ALBERT

Description: Sixty percent of Australia's wastewater treatment plants use waste stabilization pond (WSP) technology for treatment. WSP systems are most commonly used in regional and remote areas. Abstract Waste stabilization ponds (WSPs) are used extensively for the treatment of wastewater in Australia, mostly in regional and remote areas. Wastewater treatment plants (WWTPs) using pond technologies are also distributed over the full geographical extent of Australia, encompassing many climatic zones. Predominantly used to service small to medium‐sized communities, WSPs are also used to service large metropolitan Australian populations, up to 2.5 million people. When well‐maintained, WSPs are a sustainable and resilient treatment option, and treatment is achieved at significantly lower cost when compared with conventional WWTPs. Increasing population, changing regulations, and climate variability are placing increasing pressure on Australian WSP systems. Sludge accumulation over time presents a significant challenge to pond maintenance, along with increasing occurrence of toxic cyanobacterial bloom events. These challenges are only enhanced by the wide geographical distribution and by increasing operational and maintenance costs. Increased demand for recycled water is placing further pressure on Australian WSP systems, as higher value treated water is expected from WSP infrastructure that is often overloaded or under‐designed. This increased demand for high‐quality treatment presents an opportunity for operators and researchers to develop a better understanding of the coupling between hydraulics and microbial ecology of these systems. With more stringent guidelines for greenhouse gas emissions (GHGs), a better understanding of biophysicochemical processes in WSPs will lead to better estimates of GHG fluxes and variability. This information will become critical for the future planning, maintenance and operation of WSPs, and will result in a better understanding of WSP systems overall. This article is categorized under: Engineering Water 〉 Water, Health, and Sanitation Engineering Water 〉 Sustainable Engineering of Water

Description: Considerable gains have been made in controlling eutrophication in rivers, lakes and coastal areas, but much work remains to be done. Location—Great Salt Lake, Utah. Photograph by W. Wurtsbaugh. Abstract Agricultural, urban and industrial activities have dramatically increased aquatic nitrogen and phosphorus pollution (eutrophication), threatening water quality and biotic integrity from headwater streams to coastal areas world‐wide. Eutrophication creates multiple problems, including hypoxic “dead zones” that reduce fish and shellfish production; harmful algal blooms that create taste and odor problems and threaten the safety of drinking water and aquatic food supplies; stimulation of greenhouse gas releases; and degradation of cultural and social values of these waters. Conservative estimates of annual costs of eutrophication have indicated $1 billion losses for European coastal waters and $2.4 billion for lakes and streams in the United States. Scientists have debated whether phosphorus, nitrogen, or both need to be reduced to control eutrophication along the freshwater to marine continuum, but many management agencies worldwide are increasingly opting for dual control. The unidirectional flow of water and nutrients through streams, rivers, lakes, estuaries and ultimately coastal oceans adds additional complexity, as each of these ecosystems may be limited by different factors. Consequently, the reduction of just one nutrient upstream to control eutrophication can allow the export of other nutrients downstream where they may stimulate algal production. The technology exists for controlling eutrophication, but many challenges remain for understanding and managing this global environmental problem. This article is categorized under: Science of Water 〉 Water Quality Water and Life 〉 Stresses and Pressures on Ecosystems

Description: Wiley Interdisciplinary Reviews: Water, Volume 6, Issue 5, September/October 2019.

Description: Historically disadvantaged individuals still lacking proper access to water for covering their basic human needs in Post‐apartheid South Africa. Abstract Given the existence of a thriving epistemic community on water sciences, the high politicization of environmental issues in the country as well as the active mobilization of a grassroot movement inspired by environmental justice, South Africa appears to be an ideal case to study the development of a political ecology (PE) approach. Moreover, since the apartheid regime, water issues have long represented a marker of extreme inequality.This paper aims at drawing a panorama of the PE of water in South Africa, its main topics and approaches. In our definition, the PE of water is concerned with human–environment relations, with explicit considerations for power relations. In the first section, we identified texts that, according to this definition, constitute the core of the PE of water in South Africa, going beyond a mere “politics of water.” In the second section and in the discussion, we undertook an in‐depth analysis of the main topics addressed by authors, such as environmental flows, “free basic water policy,” prepaid water meters. PE of water is strongly connected to international debates about the link between water and power, but also capable of addressing in a critical way the specificities of the South African waterscape. It stems from this review that critical PE in urban settings in particular dominates the discipline. We could also note that the PE of water in rural areas tends to put a bigger emphasis on the “politics of ecology” whereas urban PE tends to focus more on the “ecology in politics,” although both thrive to examine the human–environment relations in an integrated manner. This article is categorized under: Human Water 〉 Water Governance Human Water 〉 Value of Water Human Water 〉 Rights to Water

Description: Floodwater in North Bihar, India. Photo by Luisa Cortesi. Abstract As social scientists of water, we need to keep evaluating the analytical tools we use. Through the example of floods, we here develop a critique of one of those tools, the hydrosocial cycle framework, in order to expand our conceptualizations of water. The hydrosocial cycle is a re‐elaboration of the classical hydrological cycle which explicitly politicizes and denaturalizes the study of hydrological systems. In political ecology, such a conceptual framework has been pivotal to the understanding of how water circulates in society through a complex web of power relations, economic structures, and processes that are at the same time spatial and historical. But when we deploy this concept to examine floods, a number of limitations emerge. In this article, we formulate three specific theses which focus on those limitations: (a) an overemphasis on society, (b) a lack of attention to ecology and, more generally the relationships between water and other nonhuman elements and processes, and (c) a heuristic overreliance on the metaphors of flow and cycle. In developing these three theses, we discern alternative paths of analysis to conceptualize floodwaters at a time when these events increasingly constitute a significant threat to humans and nonhumans alike. Our hope is that this critique will also contribute to broader interdisciplinary debates about water and society. This article is categorized under: Human Water 〉 Water as Imagined and Represented Water and Life 〉 Conservation, Management, and Awareness Human Water 〉 Water Governance

Description: During the 2017/2018 water crisis, city‐wide water conservation targets forced Cape Town's residents to limit their use to 50 L of water per day. Photo courtesy: Lucy Rodina. Abstract In the aftermath of the acute water crisis, building resilience in the water sector has become a priority for the City of Cape Town. In this piece, I discuss several emerging lessons from Cape Town's experience and their implications for water resilience more broadly. While having avoided “Day Zero,” Cape Town has also demonstrated how unprepared many municipalities might be as they face growing variability and uncertainty in the hydrologic cycle. Second, Cape Town's experience also signals the limits of conventional demand and supply paradigms that focus on high efficiency and overallocation of water resources. Furthermore, Cape Town's deeply unequal waterscape and acutely divisive politics are among the most important factors that shaped not only how the crisis unfolded, but also the ability of governance systems to respond in a timely and adequate manner. This article is categorized under: Engineering Water 〉 Planning Water Human Water 〉 Water Governance

Description: An example of a zoning policy whereby development has been focused onto flood safe areas combined with land‐use changes. Abstract One commonly proposed method to limit flood risk is land‐use or zoning policies which regulates construction in high‐risk areas, in order to reduce economic exposure and its vulnerability to flood events. Although such zoning regulations can be effective in limiting trends in flood risk, they also have adverse impacts on society, for instance by limiting local development of areas near the water. In order to judge whether proposed land‐use or zoning policies are a net benefit to society, they should be accepted or rejected based on a societal cost–benefit analysis (CBA). However, conducting a CBA of zoning regulation is complex and comprehensive guidelines of how to do such an analysis are lacking. We offer guidelines for good practice. In order to assess the costs and benefits of zoning as a climate change adaption strategy, they should be assessed at a societal level in order to account for public good features of flood risk reduction strategies, and because costs in one area can be benefits in another region. We propose a multistep process: first, determine the spatial extent of the zoning policy and how interconnected the zoned area is to other locations; second, conduct a CBA using monetary costs and benefits estimated from an integrated hydro‐economic model to investigate if total benefits exceed total costs; third, conduct a sensitivity analysis regarding the main assumptions; fourth, conduct a multicriteria analysis (MCA) of the normative outcomes of a zoning policy. A desirable policy is preferred in both the CBA and MCA. This article is categorized under: Engineering Water 〉 Planning Water Human Water 〉 Value of Water Science of Water 〉 Water Extremes Human Water 〉 Methods

Description: Embodied approaches to urban water in/security bring attention to the body as a critical site and scale of analysis, pushing academic and policy work to go beyond quantity/quality approaches to water to examine the ways water insecurity is tied to a host of additional inequities and vulnerabilities. In recent years, emerging scholarship has advanced embodied approaches to urban water in/security, inequality and infrastructure. This new literature is broadly informed by political ecology studies of water, which critique depoliticized approaches to water scarcity, insecurity and inequality and give attention to the socially differentiated experiences of the urban waterscape. Recent interventions to bring feminist and embodied approaches to water's urban political ecology analyze the site and scale of the body as critical for understanding everyday urban water access and inequality. Drawing from these frameworks, I summarize three contributions of an embodied urban political ecology approach for addressing water in/security. These include analytical approaches that give attention to (1) the scale of the body within multi‐scalar approaches to water, (2) intersectionality and gender/class/race/ethno‐religious relations in shaping patterns of water inequality and insecurity, and (3) everyday practices and politics, in relation to both governance and citizens, which reveal under‐theorized dimensions of water insecurity and inequality. Embodied approaches to urban water insecurity are poised to expand and deepen work on the everyday politics and lived experiences of insufficient, insecure, and unequal water that profoundly shape urban life for city‐dwellers. This article is categorized under: Engineering Water 〉 Planning Water Human Water 〉 Water Governance Human Water 〉 Rights to Water

Description: Wiley Interdisciplinary Reviews: Water, Volume 6, Issue 4, July/August 2019.

Description: Different perspectives and scales of existing causative classifications of river flood events. (Reprinted with permission from Bárdossy and Pegram (2011). Copyright 2011 Wiley and Nied et al. (2014). Copyright 2014 CC BY) Abstract A wide variety of processes controls the time of occurrence, duration, extent, and severity of river floods. Classifying flood events by their causative processes may assist in enhancing the accuracy of local and regional flood frequency estimates and support the detection and interpretation of any changes in flood occurrence and magnitudes. This paper provides a critical review of existing causative classifications of instrumental and preinstrumental series of flood events, discusses their validity and applications, and identifies opportunities for moving toward more comprehensive approaches. So far no unified definition of causative mechanisms of flood events exists. Existing frameworks for classification of instrumental and preinstrumental series of flood events adopt different perspectives: hydroclimatic (large‐scale circulation patterns and atmospheric state at the time of the event), hydrological (catchment scale precipitation patterns and antecedent catchment state), and hydrograph‐based (indirectly considering generating mechanisms through their effects on hydrograph characteristics). All of these approaches intend to capture the flood generating mechanisms and are useful for characterizing the flood processes at various spatial and temporal scales. However, uncertainty analyses with respect to indicators, classification methods, and data to assess the robustness of the classification are rarely performed which limits the transferability across different geographic regions. It is argued that more rigorous testing is needed. There are opportunities for extending classification methods to include indicators of space–time dynamics of rainfall, antecedent wetness, and routing effects, which will make the classification schemes even more useful for understanding and estimating floods. This article is categorized under: Science of Water 〉 Water Extremes Science of Water 〉 Hydrological Processes Science of Water 〉 Methods

Description: Cape Town's water crisis was triggered by a 3‐year drought leaving reservoirs with just 10% usable water. Thanks to a joint effort by government, residents, and businesses, water used dropped massively and household taps remained open until winter rains replenished dam levels. Abstract The drought that drew the world's attention to Cape Town in early 2018 was the worst on record, threatening to cut off household taps for 4 million people. Even before the drought, the city's relation to water was complex; South Africa still struggles with the legacy of racial inequality including its implications for water justice. Spatial and economic segregation of people initiated when Europeans first settled in the Cape culminated during the apartheid era 1948–1994. It forcibly moved hundreds of thousands of “colored” and “black” Capetonians to inferior housing in low‐lying areas prone to flooding and with limited access to water, sanitation, and other services. Post‐1994 policies have aimed to promote water justice for all citizens, but municipalities have struggled with implementation especially in rapidly growing informal settlements. During the recent drought, the City of Cape Town ramped up its program for water demand management, including pressure reduction, leak repairs, and public awareness‐raising campaigns. However, poor communication and a lack of trust contributed to a near‐panic situation at the threat of “Day Zero” as dams almost ran dry in the first half of 2018. Saved by winter rains, Cape Town is now exploring additional water sources and developing a new Water Strategy. Taken together, the City's experiences demonstrate that sustainable water governance needs to acknowledge the interrelated threats of drought and flooding, and the range of impacts these threats as well as the City's responses have on a population still defined by extreme inequality. This article is categorized under: Engineering Water 〉 Planning Water Human Water 〉 Water Governance Science of Water 〉 Water Extremes

Description: Comparing drought risks around the world is trickier than for other natural hazards, such as floods or earthquakes, because the impacts of droughts are hard to define. Nonetheless, metrics of hydro‐climatic variability and socio‐economic vulnerability can help to inform drought risk management policies. There is growing interest in the possibility of global analysis of drought risk, following the rapid development of global models of flood risk and other natural hazards. While this is an attractive idea, we argue that it is not actually possible as, unlike for flooding, it is not possible to unambiguously distinguish between “drought” and “nondrought” events, in particular when considering the impacts of droughts on agriculture. Any definition of a drought event depends upon the choice of drought index, which is to some extent arbitrary. Nonetheless, the absence of unambiguous quantified estimates of drought risk need not be an obstacle to rational drought risk management, as it is still possible to evaluate and compare the benefits of different drought risk management options. This article is categorized under: Science of Water 〉 Water Extremes Science of Water 〉 Water and Environmental Change Science of Water 〉 Methods

Description: Combining agent‐based (purple), sociohydrologic (orange), and drought risk (green) modelling techniques provides a generalized framework that can be used across a range of research questions. The intention of such a framework is to better represent individual and collective behaviors and their role in shaping drought risk projections. Droughts are a persistent and costly hazard impacting human and environmental systems. As climate variability continues to increase and socioeconomic development influences the distribution of wealth and people, drought risk is expected to increase in many parts of the world. The unique characteristics of droughts—namely their slow onset, large spatiotemporal extent, human‐influenced propagation, delayed impacts and teleconnection potential—make it difficult to correctly assess drought impact and calculate risk. Further complicating this calculation is the capacity for humans to make adaptive decisions before, during, and after a drought event, which in turn alters expected impacts. In this sense, droughts are equally a social and hydroclimatic issue. Risk perception is one of the main factors driving adaptation decisions, yet most models neglect how humans view and respond to risk, and in particular how experiences influence decisions through time. In this overview, we describe a framework that extends the traditional risk modeling approach to include the two‐way feedback between the transient adaptation decisions and drought exposure, vulnerability and hazard. We discuss how a sociohydrologic, agent‐based modeling setup, focused on individual and collective actions, can simulate the adaptive behaviors of different stakeholders to examine how emergent actions might influence projected drought risk. We suggest such an approach can provide a test‐bed for understanding adaptive behaviors in an increasingly drought‐prone world and could allow for better prioritization of drought adaptation strategies; refined understanding of future scenarios; and a vehicle to drive planning and resilience building. This article is categorized under: Science of Water 〉 Water Extremes Engineering Water 〉 Planning Water Engineering Water 〉 Methods

Description: Map of southern Iraq, showing ancient sites and channels along with major ancient cities. Channel data and sites (courtesy of Jaafar Jotheri and Carrie Hritz; Reprinted with permission from Jotheri (2016). Copyright 2016 Durham University; Adams (1981); Copyright 1981 University of Chicago Press; Wright (1981). Copyright 1981 University of Chicago Press) Abstract The region of southern Mesopotamia, in modern southern Iraq, was home to perhaps the world's oldest cities and complex societies. Such cities and towns developed closely to irrigation works and other water features, with major settlements developed along levees and so‐called turtle backs made up of natural accumulation and human‐made debris. While water was a critical component to the rise of cities, it was also the unique evolution of societies to their complex landscape, including the development of different social practices that made the region develop early cities. By‐products of these social developments included religious institutions and inequality but also the rise of governments, written language, laws, and other forms of social development we associate with our own societies. Recent work in southern Iraq demonstrates that the region was likely occupied much earlier than we thought; new climate data and other work will mean our picture on how the environment shaped the development of urban‐based societies in southern Mesopotamia will evolve in the coming years. New fieldwork, including surveys and excavations, will also shape a new understanding of how urbanism arose in this complex landscape. This article is categorized under: Human Water 〉 Water as Imagined and Represented Science of Water 〉 Water and Environmental Change Engineering Water 〉 Planning Water

Description: Overlap and exclusion of ES inventory and impacts from vulnerability interviews. Abstract As research recognizes the importance of ecological impacts of drought to natural and human communities, drought planning processes need to better incorporate ecological impacts. Drought planning currently recognizes the vulnerability of some ecological impacts from drought (e.g., loss of instream flow affecting fish populations). However, planning often does not identify all the ecological aspects in a landscape that stakeholders value, nor does it examine the extent to which those aspects are vulnerable to drought. One approach for identifying ecological aspects is ecosystem services (ES)—that is, the benefits humans receive from nature. To incorporate ecological impacts into drought planning in the Upper Missouri Headwaters (UMH) region (Montana, USA), we combined ES elicitation using the Common International Classification of Ecosystem Services and a vulnerability assessment using semi‐structured interviews. We juxtaposed results from the interviews and the ES elicitation to assess which ES might be vulnerable to drought and which impacts from interviews were associated with losses of ES. While both methods suggested common drought vulnerabilities, each method also suggested drought vulnerabilities not reported using the other method. The ES elicitation produced more detail about services present in the UMH ecosystem today while interviews resulted in more discussion about ecological transformation from future droughts. Results suggest that some combination of open‐ended vulnerability assessment methods and ES elicitation using a structured framework can result in greater understanding of ecological drought vulnerability in a given region. This article is categorized under: Water and Life 〉 Stresses and Pressures on Ecosystems Water and Life 〉 Conservation, Management, and Awareness Water and Life 〉 Methods Engineering Water 〉 Planning Water

Description: Dams that are commissioned, under construction, or planned for the Mekong Basin. In this paper, we examine the benefits and costs of hydropower development in the Mekong River Basin. We compare four major reports—the Mekong River Commission's (MRC's) Basin Development Plan Programme, Phase 2 (BDP2), the Strategic Environmental Assessment of Hydropower on the Mekong Mainstream (SEA), the Study on the Impacts of Mainstream Hydropower on the Mekong River (MDS), and the MRC's recent council study (CS)—in order to provide the basis for a comparative analysis of the major impact evaluation literature on mainstream dam construction in the Mekong River Basin for the period of 2010–2018. The primary objective of the review is to identify points of agreement, disagreement, inconsistency, and knowledge gaps. Both Mekong River Commission reports (BDP2 and CS) suggest extensive economic benefits for proposed hydropower development, whereas the SEA and MDS indicate that the net impact would be negative. The projected impacts of hydropower development on fisheries, sediment flows, and ecosystems vary widely both in economic and biophysical terms. However, all four reports point to decreased food security and loss of local livelihoods for millions of people as major concerns related to dam development. While considerable resources have been devoted to producing these important studies, the lack of standardization across reports, especially assumptions and methodologies for economic impacts, frustrates efforts at meaningful comparison of their findings and precludes the prospect of clear analytical outcomes or policy impacts. This article is categorized under: Engineering Water 〉 Planning Water Human Water 〉 Value of Water Engineering Water 〉 Methods

Description: High‐frequency measurements of NO3− in rivers are improving understanding of the influence of hydrological and biogeochemical processes during high flow and within stream channels. Abstract Widespread deployment of sensors that measure river nitrate (NO3−) concentrations has led to many recent publications in water resources journals including review papers focused on data quality assurance, improved load calculations, and better nutrient management. The principal objective of this study is to review and synthesize studies of high‐frequency NO3− data that have aimed to improve understanding of the hydrologic and biogeochemical processes underlying episodic, diel, and long‐term stream NO3− dynamics. Investigations have provided unprecedented detail on hysteresis and flushing patterns during high flow, seasonal variation during baseflow, and responses to multiyear climate variation. Analyses of high‐frequency data have led to notable advances in understanding how climate variation affects spatial and temporal NO3− patterns, especially dry–wet cycles and antecedent moisture. Further advances have been limited by few investigations that include high‐frequency measurements outside the channel and the short duration of many records. High‐frequency data for multiple constituents have provided new insight to the relative roles of hydrology and biogeochemistry as highlighted by studies of the roles of autotrophic uptake, denitrification, riparian evapotranspiration, and temperature‐driven changes in viscosity as drivers of diel patterns. Comparisons of short duration high‐frequency data with long duration low‐frequency data have described similarities and differences in concentration–discharge patterns and highlighted the role of legacy stores. Investigators have applied innovative analysis approaches not previously possible with low‐frequency or temporally irregular data. Future availability of long duration high‐frequency data will provide new insight to processes, resulting in improved conceptual models and a deeper understanding of the role of climate variation. This article is categorized under: Science of Water 〉 Water Quality Science of Water 〉 Methods Water and Life 〉 Nature of Freshwater Ecosystems

Description: Published literature on the floodplain restoration effectiveness monitoring was reviewed to provide historic and current monitoring methods and guidance for future monitoring and evaluation of floodplain restoration projects. Abstract Floodplains are some of the most ecologically important and human‐impacted habitats throughout the world. Large efforts are underway in North America, Europe, Australia, and elsewhere to restore floodplain habitats, not only to increase fish and aquatic biota but to restore ecological diversity. As the scale, number, and complexity of floodplain restoration projects has increased, so has the need for rigorous monitoring and evaluation to demonstrate effectiveness and guide future floodplain restoration efforts. Moreover, technological advances in remote sensing, genetics, and fish marking have been evolving rapidly and there is need to update guidance on the best methods for monitoring physical and biological response to floodplain restoration. A comprehensive review of the restoration literature located 180 papers that specifically examined the effectiveness of various floodplain restoration techniques. The various methods that were historically and currently used to evaluate the physical (channel and floodplain morphology, sediment, flow, water quality [temperature and nutrients]) and biological (fish, invertebrates, and aquatic and riparian plants) effectiveness of floodplain restoration were reviewed and used to provide recommendations for future monitoring. For each major physical and biological monitoring method, we discuss their importance, how they have historically been used to evaluate floodplain restoration, newer methodologies, and limitations or advantages of different methodologies and approaches. We then discuss monitoring the effectiveness of small (〈2 km in main channel length) and large (〉2 km of main channel length) floodplain projects, with recommendations for various study designs, parameters, and monitoring methodologies. This article is categorized under: Water and Life 〉 Conservation, Management, and Awareness Water and Life 〉 Methods

Description: Key factors influencing how density reduction alters water resources and vegetation water use, productivity and health Abstract In seasonally dry Mediterranean regions, forest ecosystems are well adapted to water stress. However, extended droughts, or droughts that are warmer or more frequent than they have been in the past, can have large consequences on water availability, forest productivity, and forest mortality. Forest density reduction offers a strategy for potentially mitigating these effects and may not only improve forest health but also increase streamflow. While recent droughts have focused attention on forest density reduction strategies, there is great uncertainty in how changing forest structure alters water availability for both remaining trees and downslope water provision, particularly during droughts in semi‐arid and Mediterranean forests. To help to disentangle sometimes conflicting findings from case studies, we present a review from an eco‐hydrologic perspective that considers both how much water trees use (hydrology) but also how water availability affects forest ecophysiology and health (ecology). This eco‐hydrologic perspective helps to build a conceptual model of the mechanisms through which changes in forest structure and composition can influence water availability, forest productivity, and mortality patterns, particularly in Mediterranean‐climate regions, both during and after droughts. Ultimately, this eco‐hydrologic conceptual model offers a guide for assessing when and where density reduction will be likely to achieve desired management objectives. This article is categorized under: Human Water 〉 Water Governance Human Water 〉 Rights to Water Science of Water 〉 Water Quality

Description: Numerical solution of Richardson–Richards equation (RRE) is an important tool to predict the flow in variably saturated soil, while this is one of the most difficult equations in hydrological community. We have reviewed several essential issues related to the development of RRE numerical models. Abstract Modeling variably saturated flow in the vadose zone is of vital importance to many scientific fields and engineering applications. Richardson–Richards equation (RRE, which is conventionally known as Richards' equation) is often chosen to physically represent the fluxes in the vadose zone when the accurate characterization of the soil water dynamics is required. Being a highly nonlinear partial differential equation, RRE is often solved numerically. Although there are mature software and codes available for simulating variably saturated flow by solving RRE, the numerical solution of RRE is nevertheless computationally expensive. Moreover, sometimes the robustness and the efficiency of RRE‐based models can deteriorate rapidly when certain unfavorable conditions are met. These demerits of RRE hinder its application on large‐scale vadose zone hydrology problems and uncertainty quantification, both of which requires many runs of the prediction model. To address these challenges, the accuracy, convergence, and efficiency of the numerical schemes of RRE should be further improved by testing a wide variety of cases covering different initial conditions, boundary conditions, and soil types. We reviewed and highlighted several critical issues related to the numerical modeling of RRE, including spatial and temporal discretization, the different forms of RREs, iterative and noniterative schemes, benchmark solutions, and available software and codes. Based on the review, we summarize the challenges and future work for solving RRE numerically. This article is categorized under: Science of Water 〉 Hydrological Processes Science of Water 〉 Methods

Description: A suggestion for 38 new water quality criteria for pesticides led us to analyze their impacts on the classification of the chemical status of a river in a Swiss canton. We discuss revision of the standards and recommend them as long as ecosystem protection is guaranteed and demonstrated. Abstract Awareness of the presence of high concentrations of pesticides in Swiss rivers has increased in the last decade. Since 2017, the Federal Department of the Environment, Transport, Energy and Communications is planning to introduce new regulatory acceptable concentrations for surface water of 38 organic pesticides. Based on pesticide concentration analyses carried out in a small agricultural catchment in the canton of Vaud, over the 2005–2015 period, we review the impacts of this legislative revision on the chemical status of rivers. A first comparison between the historical standard (0.1 μg/L) and revised water quality criteria (WQC) highlights that standards are raised for 12 pesticides and lowered for 25 pesticides, sometimes with very high ratios. Risk coefficients were computed based on the historical standard and revised WQC to determine the chemical status of the river. The worst‐case value was retained to define this status. Individual risk coefficients indicate that more pesticides meet the revised WQC than the historical one, leading to very different chemical status. According to the historical standard, the chemical status of the Boiron River is defined as moderate to poor, and the main problem is the presence of herbicides. According to the revised WQC, the chemical status is good, and periodically moderate or poor. Ninety percent of the pesticides identified had a low to very low ecotoxicological risk coefficient. Other issues related to insecticides were identified. Based on these results, we discuss the importance of the standard chosen when defining regulatory acceptable concentrations. This article is categorized under: Water and Life 〉 Conservation, Management, and Awareness Science of Water 〉 Water Quality Engineering Water 〉 Sustainable Engineering of Water

Description: Overview of methods used for reviewing irrigators' decision‐making behavior—A systematic method was used to identify key articles, and qualitative data analysis method was used to analyze the literature. Abstract The contribution of agriculture to society is undeniable, as is its impact on the environment. Irrigators' decisions to follow best management practices or implement a policy change, to accept a technology, or even to exit farming, all affect society. Hence the decision‐making behavior of irrigators is of interest to politicians, policymakers, and researchers due to their impact on resource use and social concerns for their welfare. There are numerous studies available regarding the decision‐making behavior of irrigators. Most of them concentrate on decisions within a single time frame, single decisions with multiple driving forces, or multiple decisions with a single driving force. We have conducted a comprehensive review of the existing literature related to irrigators' decision‐making behavior. We used a systematic method to identify relevant publications and used qualitative data analysis (content analysis) to analyze trends and/or patterns across the selected articles. This research provided a typology and an overarching high‐level framework of irrigators' decision‐making process irrespective of the types of decisions made. The results of the study demonstrate that it is highly beneficial to integrate both qualitative and quantitative methods in a single study to get a complete picture of irrigators' decision‐making process. This allows us to ensure that we have captured the relevant drivers of decision‐making in highly dynamic and complex environments. Better knowledge of irrigators' decision‐making process allows regulators to shape improved agricultural policy and increase acceptance by irrigators of technologies that allow water managers to allocate resources fairly among different stakeholders. This article is categorized under: Human Water 〉 Methods Engineering Water 〉 Planning Water Human Water 〉 Water Governance

Description: Over the past 15,000 years, West African populations have engaged with radical changes in environmental conditions in varied ways, leading to massive population movements, the emergence of monumentality, and the rise of cities. Abstract Since the end of the last glacial period (~12.4 ka bp) the African continent has undergone no less than 30 dramatic climate transitions. West Africa in particular witnessed abrupt climate oscillations—between humid optima and hyper‐aridity—which lasted anywhere between 10 and 15 years and a millennium. Such unpredictable shifts forced local communities to develop a suite of risk‐buffering strategies that could withstand climate change on various scales. Both archeological and palaeoclimatic research has begun to reveal how these societies engaged with their erratic environment over the span of the Holocene. The adoption of pastoral lifeways, the domestication of cereal crops, and the emergence of monumentality or urbanism may indeed be viewed through the lens of environmental risk‐buffering strategies. Yet, these developments proceeded along trajectories that belie traditional narratives rooted in environmental determinism and underscore the unique cultural processes at play, which do not conform to presumptions imported from outside regions. Revised narratives, therefore, must take into account cultural perceptions of climate change, and the localized nature of landscape. This article is categorized under: Human Water 〉 Water as Imagined and Represented Science of Water 〉 Water Extremes

Description: Conceptual framework of Critical Infrastructure Resilience and Cascades (CIRCa). Abstract Critical infrastructure and cascading effects are analyzed in this article as cross‐cutting topics in flood risk and resilience. A concept is developed for integrating aspects of disaster risk, hazard, vulnerability and resilience with critical infrastructure analytic components such as redundancy, rapidity or resourcefulness. These components are expressed for each phase of an unfolding flood event and cascading effects are indicated, too. This contribution discusses the implications of such a conceptual frame for the advancement of existing flood risk management concepts. Current international guiding strategies such as the United Nations Sendai Framework for Disaster Risk Reduction, the “Making Cities Resilient” campaigns in field of urban disaster resilience, Climate Change Adaptation processes such as the Paris Agreement of the IPCC process, or urban planning in the field of UN HABITAT are all interconnected to the topic of (critical) infrastructure. The article shows how flood risk management can connect to such wider international developments by the conceptual frame discussion presented. This article is categorized under: Engineering Water 〉 Planning Water Science of Water 〉 Water Extremes Human Water 〉 Water Governance

Description: Three component hydrograph separation results for the reference (left column) and alternative scenarios for two example rainfall‐runoff events in a small catchment derived by varying the original tracer signature of the end‐members. Abstract Hydrograph separation is a widely applied technique that uses the stable isotopes of water (2H and 18O) or other tracers to quantify the contribution of different water sources to streamflow. For its successful application it is critical to adequately characterize these sources (end‐members). In most small catchment studies, water samples are collected from end‐members at one or a few locations that are assumed to be representative for the entire catchment. We tested this assumption by reviewing 148 papers that used the stable isotopes of water to investigate hydrological processes in catchments up to 10 km2. We assessed the typical spatial variability in the isotopic composition of different hydrological compartments when they were sampled at five or more locations across a catchment. The median reported spatial variability was largest for snowmelt and soil water, followed by throughfall and shallow groundwater. To determine how this spatial variability might affect isotope‐based hydrograph separation results, we used three‐component hydrograph separation for two real rainfall‐runoff events and a synthetic rainfall‐runoff event and adjusted the isotopic composition of the end‐members (throughfall, soil water, and shallow groundwater) by the median observed spatial variability. The estimated maximum contributions of the three components differed by up to 26% from the reference scenario. This suggests that caution is needed when interpreting hydrograph separation results if they are based on samples taken at one or only a few locations. Above all, these results show that the assumption of negligible spatial variability may not be valid for small catchments. This article is categorized under: Science of Water 〉 Hydrological Processes Science of Water 〉 Methods

Description: The Bridge of the Admiral across the river bed of the Oreto, Palermo. The Muslim capture of Palermo in 831 transformed a small Byzantine outpost into the capital of Islamic Sicily and a Mediterranean metropolis. Central to this urban growth was Palermo's role as an agricultural and trading hub: the city's geophysical situation on the north‐western shores of Sicily linked it with a fertile plane where rivers flowed north into the Tyrrhenian Sea. Throughout the medieval period, Palermo's dependence on this area's water resources made questions of water use and management a key concern in the medieval city. However, there has been little scholarly debate about such issues. With an eye to recent archeological studies concerning the Oreto districts, this article will explore such dynamics by analyzing an important piece of architecture which crosses the Oreto river: the so‐called Bridge of the Admiral. This bridge was recently made a UNESCO World Heritage Site and is considered one of the most significant works of medieval Mediterranean engineering. Until now, research has concentrated on questions of its date and commissioning: scholarship has largely assumed that it was constructed in 1132 by George of Antioch, the admiral of King Roger II. However, as this article will demonstrate, there is little evidence to support this conclusion. This study will approach the debate by analyzing the spatial setting of the bridge. In so doing, it will be shown how an investigation of the bridge's toponym and topography can elucidate details concerning both the bridge's commissioning and the institutional relationship between the Oreto area and the city of Palermo. This article is categorized under: Human Water〉 Water as Imagined and Represented Human Water〉 Water Governance

Description: Journal articles in highly cited water‐related journals on “resilience” underline the rising usage and continuing trend since at least a decade in flood risk management (FRM). Abstract Resilience in relation to flood risk management (FRM) is not a new concept, yet parts of the FRM community are still struggling to apply it. The main challenge this study addresses is the question as to whether parts of the FRM community should still adopt, or rather “leap‐frog,” resilience. The main purpose is to evaluate whether resilience is a still on‐going trend or, already subsiding. Research suggests that resilience is an on‐going trend that connects research and policy and has gained international recognition as expressed by international guidelines and bodies promoting its research but also its operationalization. Academic literature in the area of FRM also shows a significant continuing development. Resilience enables to analyze dynamics and transformations of riverine areas, or coastal zones in connection to an integrated social‐environmental system approach with more emphasis and conceptual basis than previous concepts. Resilience is more than a short‐lived notion and it appears that FRM researchers cannot avoid addressing it. Resilience often is a convergence of ideas and mainstreaming of efforts, which in many venues is absolutely necessary and can help, for example, to decrease silo‐thinking. But as academics, we have a mandate to remain skeptical and remain on the look‐out for novel ideas, too. This article is categorized under: Engineering Water 〉 Planning Water

Description: Humans and the landscape interacting over the course of 3,500 years have led to the rise and fall of major civilizations in the Teotihuacan Valley. The changing times have brought with them varying landscapes and different peoples and practices–independent, yet inexorably linked with each other. The Teotihuacan Valley has witnessed the rise and fall of various civilizations since it was first inhabited by sedentary societies 3,500 years ago. Given its location in a semi‐arid environment, Teotihuacan has featured prominently in debates about the role of water and water management in the development of sedentism, culture, primary states, and large, complex societies. While many previous discussions tended to echo Wittfogel's “hydraulic hypothesis,” focusing on the ability of an elite few to monopolize water resources, we instead turn to a growing corpus of research showing varied water management strategies through time potentially resulting in distinct patterns of social organization. In this palimpsest landscape hydraulic and agricultural strategies were constrained not merely by present environmental conditions, but also by very real and material legacies of previous behavior. We discuss the state of research regarding these adaptations (and social responses) to water scarcity from the Early‐to‐Middle Formative Period (1250–650 B.C.) through the independence of Mexico (A.D. 1810), noting how previous fundamental assumptions about agriculture and hydraulic management in the Teotihuacan Valley have led to a significant number of neglected concepts and potential adaptations. If we are to address the current destruction of the Teotihuacan Valley's ecological and cultural resources in response to national development and climate change, a historical‐ecological perspective is necessary to disentangle the relevant processes that have shaped the landscape—and the cultures residing within it—to this day. This article is categorized under: Science of Water 〉 Methods Human Water 〉 Water as Imagined and Represented Engineering Water 〉 Planning Water

Description: Dimensional analysis has historically represented a powerful tool that, while bypassing the intricacies of turbulence theory and the NS equations, allows for the derivation of many formulae that are still routinely used in many problems of practical interest dealing with highly turbulent flows. The use of this concept to describe water movement in streams as well as water vapor movement in the atmosphere is featured. The apparent random swirling motion of water is labeled “turbulence,” which is a pervasive state of the flow in many hydrological and hydraulic transport phenomena. Water flow in a turbulent state can be described by the momentum conservation equations known as the Navier–Stokes (NS) equations. Solving these equations numerically or in some approximated form remains a daunting task in applications involving natural systems thereby prompting interest in alternative approaches. The apparent randomness of swirling motion encodes order that may be profitably used to describe water movement in natural systems. The goal of this primer is to illustrate the use of a technique that links aspects of this ordered state to conveyance and transport laws. This technique is “dimensional analysis”, which can unpack much of the complications associated with turbulence into surprisingly simplified expressions. The use of this technique to describing water movement in streams as well as water vapor movement in the atmosphere is featured. Particular attention is paid to bulk expressions that have received support from a large body of experiments such as flow‐resistance formulae, the Prandtl‐von Karman log‐law describing the mean velocity shape, Monin‐Obukhov similarity theory that corrects the mean velocity shape for thermal stratification, and evaporation from rough surfaces. These applications illustrate how dimensional analysis offers a pragmatic approach to problem solving in sciences and engineering.

Description: Attenuation data from commercial microwave links can provided valuable rainfall information. But there are several challenges along the way from raw data access to rainfall fields. Accurate observation of the high spatio‐temporal variability of rainfall is crucial for hydrometeorological applications. However, the existing observations from rain gauges and weather radars have individual shortcomings that can introduce considerable errors and uncertainties. A fairly new technique to get additional rainfall information is the usage of the country‐wide commercial microwave link (CML) networks for rainfall estimation by exploiting the measurements of rain‐induced attenuation along these CMLs. This technique has seen an increasing number of applications during the last years. Different methods have been developed to process the noisy raw data and to derive rainfall fields. It has been shown that CMLs can provide important line‐integrated rainfall information that complements pointwise rain gauge and spatial radar observations. There exist several limitations, though. Robustly dealing with the erratic fluctuations of the CML raw data is a challenge, in particular with the growing number of CMLs. How to correctly compensate for the biases from the effect of wet antenna attenuation for different CMLs also remains a crucial research question. Progress is additionally hampered by the lack of method intercomparisons, which in turn is hampered by restricted data sharing. Hence, collaboration is key for further advancements, also with regard to extended interaction with the CML network operators, which is a prerequisite to achieve increased data availability. In regions where rain gauges and weather radars are available, CMLs are a welcome complement. But in developing countries, which are characterized by weak technical infrastructure and which often suffer from water stress, additional rainfall information is a necessity. CMLs could play a crucial role in this respect. This article is categorized under: Science of Water 〉 Hydrological Processes Science of Water 〉 Water Quality Science of Water 〉 Methods

Description: The Upper Streenbras dam in Cape Town back in 2016, one year into the three year drought that led to the acute water shortages in Cape Town. Resilience is increasingly applied the context of water systems, and water governance more broadly, in response to climate change impacts, hydrologic variability and uncertainty associated with various dimensions of global environmental change. However, the meanings, applications and implications of resilience as it relates to water governance are still poorly understood. Drawing on a systematic scoping review of the peer‐reviewed academic literature, this paper addresses the questions: how is resilience framed in relation to water systems and water governance, how are diverse resilience framings (re)shaping ideas and trends in water management, and what are the associated implications? The analysis found that the resilience‐informed water governance literature remains fragmented and predominantly centered on conventional approaches and framings of water planning, with a predominant focus on engineering resilience in water supply infrastructure. A recently emerging engagement with resilience in the water governance literature, however, draws on more diverse framings and theories and calls for a shift towards more integrative and ecologically‐centered thinking in water governance. Despite this, significant empirical and conceptual gaps remain, particularly around the integration of the various subsectors of water governance and, more importantly, around the institutional and governance dimensions of building water resilience. This article is categorized under: Engineering Water 〉 Planning Water Human Water 〉 Water Governance

Description: High‐quality contingent valuation studies can estimate the value communities place on potable water resources. Determining the value of environmental goods that impact human populations, such as potable water, is often highly problematic. The all‐too‐common lack of realistic markets for the provisioning of these goods necessitates the use of nonmarket valuation techniques. Contingent valuation surveys are often an appropriate method, thanks to their ability to value hypothetical changes and nonuse values, and their limited prior data requirements. When properly implemented, contingent valuation surveys can estimate the maximum willingness to pay of surveyed individuals, allowing the value of the environmental good to be accurately measured. An analysis of the extant body of contingent valuation studies of rural potable water systems in developing and emerging countries indicates that rural water consumers are willing to pay, often substantially, for the creation of a potable water system or for improvements to existing system. Studies involving changes to existing potable water system, through improving an existing system for greater reliability or sustainability, showed a high degree of consistency in respondents' willingness to pay estimates as a percentage of income or current water tariff. Higher incomes, higher levels of education and youth, among other characteristics, were found to be positively correlated with higher willingness to pay estimates. Future contingent valuation studies focusing on improving comparability through greater methodological consistency, and addressing the impact of community power dynamics, intercommunal cleavages, and subsidies could be especially productive. This article is categorized under: Human Water 〉 Value of Water Engineering Water 〉 Planning Water Human Water 〉 Water Governance

Description: Wiley Interdisciplinary Reviews: Water, Volume 6, Issue 2, March/April 2019.

Description: Urban aquatic ecosystems provide multiple co‐benefits including opportunities for recreations, cooling, flood alleviation and urban nature. How much biological diversity is present and how variations may differentially relate to variation in health outcomes is less understood (Wandsworth Common, UK. Courtesy of B. Goldsmith). The findings of a national workshop that explored the social and environmental impacts, challenges, and research opportunities associated with the role of urban freshwaters for improved public health are discussed. Bringing together the collective expertise of academics, practitioners, policy, and user‐groups from urban aquatic ecology and human health backgrounds, this commentary develops a progressive agenda for future research by synthesizing current understandings and knowledge of urban aquatic biodiversity relative to health‐related ecosystem service outcomes, from a cross‐sectoral and cross‐disciplinary perspective. Key areas include (a) a need for greater interaction between sectors to maximize opportunities for collaboration and to promote the cobenefits (both environmental and health) associated with urban freshwater ecosystems; and (b) the need for a unified understanding and operationalization of the definition of aquatic biodiversity across sectors and disciplines, to improve our understanding of whether actual freshwater biodiversity or the perception of biodiversity is important for maximizing gains in health. Methods of valuation relating to ecosystem services and resource allocation and investment in urban freshwaters are critical in ensuring that research addresses the pathways and contexts within which health and environmental benefits from blue space can be maximized. This article is categorized under: Human Water 〉 Value of Water

Description: Caracol, Belize, and Tikal, Guatemala, are two of the largest and best documented ancient cities in the Southern Maya lowlands. Each occupies a distinct agro‐urban landscape, shown through geographic information system analysis, and has a unique urban morphology of built environmental features for management of potable and agricultural water resources. The Classic Period Maya cities of Caracol and Tikal possessed unique urban morphologies of water management. In part, the built environment at each city reflects adaptations to the hydrology of their landscapes. Caracol exists in a rugged, hilly, and karst environment; its residents invested their landesque capital in constructing agricultural terraces and residential reservoirs. These features created Caracol's anthropogenic garden‐city landscape. This landscape was unified through a dendritic causeway system and the distributed nature of monumental nodes. The landscape of Tikal exhibits a lower slope, is generally smoother, and its residents invested in constructing a large and condensed site core along with their monumental reservoirs. Additionally, the people of Tikal invested in bajo margin agriculture. The differences in urban form and hydrology conditioned the resulting water management strategies employed by both cities; the resulting built environmental features are preserved in the archeological record. Because of its higher slopes, Caracol's landscape presents a greater hazard for soil erosion and faster rainfall runoff. Yet, the construction of distributed residential reservoirs and agricultural terraces acted to collect rainfall, increase soil saturation, and reduce this runoff. Tikal's landscape on the whole presents fewer hazards in terms of soil erosion but perhaps greater issues from torrential rainfall. Water management infrastructure at both cities reflects both their unique urban morphologies and environmental conditions. This article is categorized under: Engineering Water 〉 Planning Water Science of Water 〉 Methods

Description: Sketch of return period and probability of failure. The return period measures the rareness of extreme events such as floods and droughts that might cause huge damages to the society and the environment; hence, it lies at the heart of hydraulic design and risk assessment problems. Indeed, return period is a commonly applied probabilistic concept in the hydrologic literature, which has attracted renewed interest stimulated by the need of efficiently dealing with complex processes in a changing environment. In this study, the concept of return period and the related risk of failure are presented by making use of a general mathematical framework. It helps for a better understanding of the return period and risk of failure formulations that are commonly adopted in practical engineering applications. The framework can be further applied under more general conditions. In particular, the extension of the return period concept to nonstationary and time‐dependent cases is discussed herein, by relaxing the hypotheses commonly (and sometimes implicitly) assumed that allows to derive simple analytic formulations. This article is categorized under: Engineering Water 〉 Planning Water Engineering Water 〉 Methods Science of Water 〉 Methods

Description: A flash flood and its forensic analysis. The last decade has witnessed the development of methodologies for the post‐flood documentation of both hydrogeomorphological and social response to extreme precipitation. These investigations are particularly interesting for the case of flash floods, whose space–time scales make their observations by conventional hydrometeorological monitoring networks particularly challenging. Effective flash flood documentation requires post‐flood survey strategies encompassing accurate radar estimation of rainfall, field and remote‐sensing observations of the geomorphic processes, indirect reconstruction of peak discharges—as well eyewitness interviews. These latter can give valuable information on both flood dynamics and the related individual and collective responses. This study describes methods for post‐flood surveys based on interdisciplinary collaborations between natural and social scientists. These surveys may help to better understand the links between hydrometeorological dynamics and geomorphic processes as well as the relationship between flood dynamics and behavioral response in the context of fast space–time changes of flooding conditions. This article is categorized under: Science of Water 〉 Methods Science of Water 〉 Hydrological Processes

Description: The cover image is based on the Advanced Review Commercial microwave link networks for rainfall observation: Assessment of the current status and future challenges, by Christian Chwala and Harald Kunstmann, https://doi.org/10.1002/wat2.1337 The cover image is based on the Advanced Review Commercial microwave link networks for rainfall observation: Assessment of the current status and future challenges, by Christian Chwala and Harald Kunstmann, https://doi.org/10.1002/wat2.1337

Description: We discuss the impact of a changing regional hydroscape (pictured) on the proxy archives and people of southwest Asia over the last 20,000 years. The Fertile Crescent, its hilly flanks and surrounding drylands has been a critical region for studying how climate has influenced societal change, and this review focuses on the region over the last 20,000 years. The complex social, economic, and environmental landscapes in the region today are not new phenomena and understanding their interactions requires a nuanced, multidisciplinary understanding of the past. This review builds on a history of collaboration between the social and natural palaeoscience disciplines. We provide a multidisciplinary, multiscalar perspective on the relevance of past climate, environmental, and archaeological research in assessing present day vulnerabilities and risks for the populations of southwest Asia. We discuss the complexity of palaeoclimatic data interpretation, particularly in relation to hydrology, and provide an overview of key time periods of palaeoclimatic interest. We discuss the critical role that vegetation plays in the human–climate–environment nexus and discuss the implications of the available palaeoclimate and archaeological data, and their interpretation, for palaeonarratives of the region, both climatically and socially. We also provide an overview of how modelling can improve our understanding of past climate impacts and associated change in risk to societies. We conclude by looking to future work, and identify themes of “scale” and “seasonality” as still requiring further focus. We suggest that by appreciating a given locale's place in the regional hydroscape, be it an archaeological site or palaeoenvironmental archive, more robust links to climate can be made where appropriate and interpretations drawn will demand the resolution of factors acting across multiple scales. This article is categorized under: Human Water 〉 Water as Imagined and Represented Science of Water 〉 Methods Water and Life 〉 Nature of Freshwater Ecosystems

Description: Controls on the delivery, transport and storage of fine sediment, and the resulting ecological responses in river networks. From the sediment sources in the landscape to the ecological impact in the river, the transport of particles and the responses of biota are subject to potential lags and delays as sediment is temporarily stored and time is taken for local populations to reach critical life‐stages where fine sediment limits survival. Excess fine sediment, comprising particles 〈2 mm in diameter, is a major cause of ecological degradation in rivers. The erosion of fine sediment from terrestrial or aquatic sources, its delivery to the river, and its storage and transport in the fluvial environment are controlled by a complex interplay of physical, biological, and anthropogenic factors. While the physical controls exerted on fine sediment dynamics are relatively well‐documented, the role of biological processes and their interactions with hydraulic and physicochemical phenomena has been largely overlooked. The activities of biota, from primary producers to predators, exert strong controls on fine sediment deposition, infiltration, and resuspension. For example, extracellular polymeric substances associated with biofilms increase deposition and decrease resuspension. In lower energy rivers, aquatic macrophyte growth and senescence are intimately linked to sediment retention and loss, whereas riparian trees are dominant ecosystem engineers in high energy systems. Fish and invertebrates also have profound effects on fine sediment dynamics through activities that drive both particle deposition and erosion depending on species composition and abiotic conditions. The functional traits of species present will determine not only these biotic effects but also the responses of river ecosystems to excess fine sediment. We discuss which traits are involved and put them into context with spatial processes that occur throughout the river network. While strides towards better understanding of the impacts of excess fine sediment have been made, further progress to identify the most effective management approaches is urgently required through close communication between authorities and scientists. This article is categorized under: Water and Life 〉 Nature of Freshwater Ecosystems Water and Life 〉 Stresses and Pressures on Ecosystems Science of Water 〉 Water and Environmental Change

Description: Wastewater irrigation began with the water shortage, fertilizer saving or preventing water pollution centuries ago, developed with the technological innovations, and still faces many challenges in the future. This is a broad and systematic overview of the history, the present status and the challenges in future focused on wastewater irrigation. With population growth and social and economic development, water shortage is becoming a serious issue worldwide. As a key alternative water resource, wastewater can be used in agriculture to compensate for water shortages. Wastewater irrigation has a long development history and has undergone different phases in developing and developed countries. Untreated wastewater irrigation can come with numerous environmental problems. Strong management practices, such as the application of suitable treated and irrigated technologies, can be used to reap substantial benefits while minimizing risks. We discussed the major challenges associated with wastewater irrigation and its future use to help improve wastewater irrigation practices around the world. This article is categorized under: Engineering Water 〉 Sustainable Engineering of Water Engineering Water 〉 Water, Health, and Sanitation

Description: Simulation modeling of nonmarket water exchanges: Exchange strategies reach different stable arrangements depending on the population of partners. Abstract Water allocation occurs within systems that include market‐driven and nonmarket approaches; these are often nested within complex collections of laws, contracts, and customs, and embody cultural definitions of the nature of water as a commodity or a right and the nature of fair exchanges. Understanding the dynamics of such an allocation system, including the ways that it may change through time and the ways that it can be modified to better achieve societal goals, can be challenging. One promising approach is agent‐based modeling (ABM), and specifically models in which the agents dynamically adapt to the system that they create. The potential for such modeling in the domain of water systems is only beginning to be explored. We present a highly abstract but illustrative example of an adaptive system and its analysis to show the potential for the ABM approach. This article is categorized under: Engineering Water 〉 Planning Water Human Water 〉 Rights to Water Engineering Water 〉 Methods Human Water 〉 Water Governance

Description: Interpreting responses to the World Commission on Dams' (WCD) report and recommendations. Abstract The World Commission on Dams (WCD) was a global environmental governance forum that worked between 1998 and 2000 to try to resolve long‐standing controversies between supporters and opponents of large dams. Its objectives were to assess the development effectiveness of large dams and to develop best practice guidelines for large dam construction and management, based on an extensive review of scientific evidence and wide‐ranging stakeholder consultation. This paper reviews literature discussing the WCD, to understand its influence on the debate on large dams and beyond. We find that its influence is debated within four main contexts: (a) interpretations of stakeholder responses to the WCD report and recommendations; (b) the persistence of the kinds of impacts of large dams that gave rise to the Commission's work; (c) the different visions for appropriate follow‐up strategies; and (d) insights from the WCD experience in the context of global environmental governance. Within these four contexts, we identify diverse opinions and directions of post‐WCD development and sources of disagreement on its merits and legacy, ranging from calls for its full implementation to dismissal and opposition. Commentators also differ in their assessment of whether the WCD sparked truly novel insights and propositions for dam decision‐making or whether it simply represented one among many other elements in the broader debate on dams. Most commonly, the WCD's work is cited in the context of persistent negative social and environmental impacts of dams: neither the impacts nor the controversy over large dams have ended. This article is categorized under: Engineering Water 〉 Planning Water Engineering Water 〉 Sustainable Engineering of Water

Description: The Tigris and Euphrates basin is shared by Turkey, Syria, Iraq, and Iran (with a small portion of the watershed in Saudi Arabia and Jordan). Many major dams now regulate and divert the flow of these rivers. These facilities, and the water delivery systems associated with the rivers, have become significant targets and weapons of armed conflict in the region in recent years. Abstract Violence over water resources has persisted in various forms for thousands of years, driven by complex ideological, religious, economic, and strategic factors. Scarce and valuable freshwater has played a role in conflicts as a contributing factor, a target or tool, or a weapon. The focus of this review is on specific instances of violence around water and water systems conflict in Syria, Iraq, and Yemen, where water resources and human‐built water systems have been both weapons and targets of conflict. A new cycle of violence in the region, growing in extent and severity, began approximately three decades ago and is described here in the context of broader regional water challenges and theoretical issues around environmental security. New data and definitions and an analysis of the types of event and sources of information are also provided in the context of international humanitarian law. This assessment confirms and expands upon previous work that evaluates trends toward the weaponization of water and the targeting of water systems in Middle East conflicts. Initial recommendations for reducing these trends are provided. This article is categorized under: Human Water 〉 Water Governance Human Water 〉 Rights to Water Science of Water 〉 Water Quality

Description: Overcoming balkanization in water market research to explore the role of markets in achieving SDG 6. Abstract Water markets are used in a wide variety of contexts to (a) increase access to water, and (b) increase water use efficiency by reallocating water to uses with a higher economic value. The global prevalence of water markets may help or hinder achievement of Sustainable Development Goal 6, making it essential to understand their role in water management. However, an overarching understanding of what water markets are and how they work across different regulatory and geographic contexts is surprisingly elusive. The literature separates water markets based on their formality and the nature of the goods and services being sold (typically either domestic water or agricultural), but growing water scarcity and increasing urban water demands means that agricultural and urban water use can no longer be considered separately. This review brings together two disparate strands of literature on water markets: (a) markets as a tool for re‐allocation between agricultural uses (including both water rights and irrigation services), and (b) urban water markets to expand access to safe water supplies. Based on a review of 148 studies of water markets, this article explores the similarities and differences between urban and agricultural markets across the spectrum of regulatory formality to identify key findings in water market operation and outcomes, including critiques of market function. Bringing together the work on urban and agricultural water markets highlights important lessons on the role water markets can play in achieving SDG 6. This article is categorized under: Human Water 〉 Value of Water Engineering Water 〉 Sustainable Engineering of Water

Description: Use of emerging technology is transforming how we see riverscapes. Plugging‐in tools and workflows to conceptual frameworks such as River Styles provides scaffolded and coherent datasets for use in river management. But, humans are not redundant! We are needed to choose the right tools for the job, interrogate and validate output(s), and make geomorphic and management interpretations of rivers. Abstract In an era of big‐data acquisition and semiautomation of geomorphic river surveys, it is timely to consider how to better integrate this into existing and widely used conceptual frameworks and approaches to analysis. We demonstrate how Stage 1 of the River Styles Framework, which entails identification and interpretation of river character and behavior, patterns and controls, can be used as a “powerboard” into which available, developing and future semiautomated tools and workflows can be plugged (or unplugged). Prospectively, such approaches will increase the efficiency and scope of analyses, providing unprecedented insights into the diversity of rivers and their morphodynamics. We appraise the role of human decision‐making in conducting expert‐manual analyses and interpretations. Genuine integration of big‐data analytics, remote‐sensing based tools for semiautomated river analysis with expert‐manual interpretations including field insights, will be an essential ingredient to fully exploit emerging computational and remote sensing technologies to advance our understanding of river systems, to translate information into knowledge, and raise the standards of practice in river science and management. This article is categorized under: Water and Life 〉 Conservation, Management, and Awareness Water and Life 〉Methods Engineering Water 〉 Planning Water Engineering Water 〉 Sustainable Engineering of Water

Description: Abstract Plastic pollution in aquatic ecosystems is an emerging environmental risk, as it may negatively impacts ecology, endangers aquatic species, and causes economic damage. Rivers are known to play a crucial role in transporting land‐based plastic waste to the world's oceans, but riverine ecosystems are also directly affected by plastic pollution. To better quantify global plastic pollution transport and to effectively reduce sources and risks, a thorough understanding of origin, transport, fate, and effects of riverine plastic debris is crucial. In this overview paper, we discuss the current scientific state on plastic debris in rivers and evaluate existing knowledge gaps. We present a brief background of plastics, polymer types typically found in rivers, and the risk posed to aquatic ecosystems. Additionally, we elaborate on the origin and fate of riverine plastics, including processes and factors influencing plastic debris transport and its spatiotemporal variation. We present an overview of monitoring and modeling efforts to characterize riverine plastic transport, and give examples of typical values from around the world. Finally, we present an outlook to riverine plastic research. With this paper, we aim to present an inclusive and comprehensive overview of riverine plastic debris research to date and suggest multiple ways forward for future research. This article is categorized under: Science of Water 〉 Water Quality Water and Life 〉 Stresses and Pressures on Ecosystems

Description: Causal structure depicting influent (tributary) flow and influent (tributary) nutrient concentration as the direct causes of both lake nutrient concentration and nutrient load. The absence of an arrow from nutrient load to lake nutrient concentration indicates that the correlation between nutrient load and lake nutrient concentration is not causal. The dashed arrow from influent flow to influent nutrient concentration indicates that nutrient concentration in the tributary may be dependent on flow. Abstract The “phosphorus loading concept,” or more generally the “nutrient loading concept,” arose from Richard Vollenweider's work in the 1960–1970s that showed correlations between phosphorus loads and various eutrophication symptoms. The initial success of target loads developed for the Great Lakes solidified the concept that nutrient loading causes eutrophication, and load targets have become common tools to reduce eutrophication. Using concepts from the field of causality, we offer additional context to the nutrient loading concept to show that the correlation between nutrient load and eutrophication is spurious; load and eutrophication have common drivers, tributary flow and tributary nutrient concentration, but load itself is not causal. Consequently, in‐lake conditions are not invariant to the same load delivered at differing flow‐concentration combinations. We then use a simulation model to evaluate the consequences of delivering the same load at various flow‐concentration combinations from the Maumee River into Lake Erie. We show that load reductions under increased tributary flows may cause in‐lake phosphorus concentration increases, potentially offsetting the anticipated effect of the load reduction. Thus, particularly under a scenario where climate change may cause systematic flow changes, it will be important to expand the nutrient loading concept to consider the independent effects of tributary flow and nutrient concentrations, to assess the effectiveness of nutrient reduction strategies. This article is categorized under: Science of Water 〉 Hydrological Processes Water and Life 〉 Stresses and Pressures on Ecosystems Science of Water 〉 Water Quality

Description: Artificial light at night can occur as a form of environmental pollution, light pollution, which also affects aquatic systems. We identify a knowledge gap of insufficient data regarding the status quo of aquatic light pollution and provide a route to fill this gap with in‐situ measurements. Abstract Freshwater ecosystems are hotspots of biodiversity. They are of major importance for humans because they provide vital ecosystem services. However, as humans tend to settle near freshwaters and coastal areas, these ecosystems are also over‐proportionally affected by anthropogenic stressors. Artificial light at night can occur as a form of environmental pollution, light pollution. Light pollution affects large areas on a worldwide scale, is growing exponentially in radiance and extent and can have diverse negative effects on flora, fauna and on human health. While the majority of ecological studies on artificial light at night covered terrestrial systems, the studies on aquatic light pollution have unraveled impact on aquatic organisms, ecosystem functions as well as land‐water‐interactions. Although monitoring of light pollution is routinely performed from space and supported by ground‐based measurements, the extent and the amount of artificial light at night affecting water bodies is still largely unknown. This information, however, is essential for the design of future laboratory and field experiments, to guide light planners and to give recommendations for light pollution regulations. We analyze this knowledge gap by reviewing night‐time light measurement techniques and discuss their current obstacles in the context of water bodies. We also provide an overview of light pollution studies in the aquatic context. Finally, we give recommendations on how comprehensive night‐time light measurements in aquatic systems, specifically in freshwater systems, should be designed in the future. This article is categorized under: Water and Life 〉 Stresses and Pressures on Ecosystems Water and Life 〉 Conservation, Management, and Awareness Water and Life 〉 Methods

Description: WIREs Water , EarlyView.

Description: Following Hurricane Katrina in August 2005, residents of Jefferson Parish, Louisiana, especially children and older people, are brought to an elevated bridge area by boat (photograph by Win Henderson: Available at: https://commons.wikimedia.org/wiki/File:FEMA_-_14535_-_Photograph_by_Win_Henderson_taken_on_08-31-2005_in_Louisiana.jpg (accessed at May 9, 2019).). Abstract The management of hydrometeorological hazard risks increasingly builds on the notion that the main constituents—hazard risk and vulnerability—have to be understood as dynamic processes. Natural hazards and their impacts are influenced by changes in land use and impacts of climate change, whereas the vulnerability of communities is, inter alia, determined by changes in their demographic composition. Structurally weak rural regions have to face these challenges, while their capacities to manage hydrometeorological risks are affected by major demographic developments, such as population decline and demographic aging (especially in Europe). Nonetheless, academic research regarding this issue is still in its infancy. Research on the relationship between hydrometeorological hazards and long‐term demographic change often focuses on one side of the coin: impacts of hazards on the demographic composition of communities. The impacts of demographic change onto communities' ability to prepare for, respond to and recover from natural hazards appear as disregarded link. This article gives an overview over linkages by reviewing literature at the intersection of demographic and hydrological hazard research. The review of more than 90 publications provides insights into how particular demographic factors (socioeconomic status; migration, residency, and mobility; gender and gender relations; education and knowledge; and religion and beliefs) determine the management of hydrometeorological hazard risks. Furthermore, it identifies publications which consider long‐term developments. The overview shows that we lack a thorough connection between demographic change and hydrometeorological hazard risk management, which would be crucial for in‐depth studies as well as a more dynamic understanding of respective linkages. This article is categorized under: Science of Water 〉 Water Extremes Engineering Water 〉 Planning Water

Description: Proposed regulatory framework to protect groundwater resources during UOG extraction Abstract Unconventional oil and gas (UOG) extraction using fracking can damage groundwater resources, a crucial resource in many countries. Protecting groundwater will become more urgent as climate change and population growth increase pressure on water demand, especially in water‐scarce countries. But despite the strategic importance of groundwater, it is often poorly managed during UOG extraction. This review considers three types of regulation (command‐and‐control, market‐based and voluntary) in countries where UOG extraction is allowed, to identify the best suite of regulations to protect groundwater resources during this process. We propose a regulatory framework that includes both “hard” command‐and‐control regulations and “soft” market‐based and voluntary regulations. If regulations are to protect groundwater resources effectively, public disclosure of UOG operations must be required and the information must be stored in publicly accessible databases. This would allow for independent scientific review of data by academia and the private sector, in addition to government scrutiny of the data. These parties can then make recommendations to government, allowing timeous and appropriate adaptive management and the amendment of regulations as necessary. And, most importantly, these regulations must be properly enforced to avoid (in some cases irreversible) damage to groundwater resources. This article is characterized under: Engineering Water 〉 Sustainable Engineering of Water Human Water 〉 Water Governance Science of Water 〉 Water Quality

Description: Velocity is a dynamic and highly localized component of river discharge. Areas of intense velocity can create barriers to migration for fish. But, understanding relations between river discharge and the biological implications of local hydraulic barriers has only recently become possible. High resolution digital elevation models derived from drones are useful in characterizing these hydraulic features at the scale at which migrating fish experience them. Below is a an orthorphoto mosaic of study reach overlaid with modeled velocity (m/s) at survey discharge. Abstract Global climate models suggest dramatic changes in the timing and form of future precipitation in the Pacific Northwest, United States. By some estimates, in the Columbia River drainage, basin‐wide snow‐water equivalencies could decrease by more than 50% before the end of the century, with locally more extreme variation. In the South Fork Clearwater River, Idaho, where hydraulic barriers are currently thought to partially limit ESA‐listed steelhead migrations, changes in precipitation that could exacerbate the intensity and timing of hydraulic barriers presents an obvious conservation concern. Evidence indicates that the strongest steelhead swimmers are capable of sustaining burst speeds for up to 20 s, with maximum speed being a function of fish size (length). Understanding hydraulic dynamics that have implications for migrating fish requires integration of high‐resolution hydraulic models with sufficient resolution to characterize the hydraulic experience of the fish. Unmanned aerial vehicles (drones) have recently emerged as useful platforms for measuring river ecosystems with high precision. Results from habitat surveys and hydraulic modeling can identify locations where intense hydraulic energy may preclude fish passage during critical migration periods. The current as well as future range of discharges can be evaluated with a spatially explicit hydraulic model to quantify when, where, and how long barriers to migration exist. Further, this approach provides a powerful tool for manipulating the digital physical channel form and presents a heuristic opportunity to test hydraulic scenarios to improve migration success. This article is categorized under:   Water and Life 〉 Nature of Freshwater Ecosystems   Water and Life 〉 Stresses and Pressures on Ecosystems   Water and Life 〉 Methods

Description: The ineffectiveness of state‐centered groundwater governance must be understood through a political analysis of state‐society relationships. Favorable drivers and contexts for state‐centered governance are identified but shown to be rare in practice. Abstract Faced with severe groundwater depletion, many governments have opted to increase the power of the state. Despite calls for more inclusive governance and a role for groundwater users, modes of governance have tended to continue to rely on a diversity of policy tools and state‐run strategies in the attempt to control groundwater (over)abstraction. Yet, around the world, the performance of state‐centered governance has remained dismal. Beyond common difficulties in terms of data and financial or human resources, this article analyzes in greater depth the limited effectiveness of state groundwater policies that has been observed, emphasizing its political ramifications. The various aspects of weak monitoring and enforcement, as well as of the infamous “lack of political will,” are considered from the perspective of the political economy of groundwater economies. Cases of relative success are then used to identify favorable drivers and contexts for effective state‐centered groundwater governance. This article is categorized under: Human Water 〉 Water Governance Engineering Water 〉 Planning Water

Description: Water issues are always local, even when transboundary. Therefore, efforts to manage these resources should be pursued and implemented at the local and regional levels, regardless of binding or nonbinding nature of any arrangements. Abstract Binational efforts to understand, assess, and manage shared groundwater resources on the Mexico‐Texas border are limited and politically sensitive. On the Mexico side, long‐standing centralized groundwater governance structures have created institutional barriers at the local level to the expansion of knowledge and cooperation over these transboundary resources. On the Texas side, property rights related to groundwater resources limit the scope of options available for cooperative management of cross‐border aquifers. In order to develop more effective cross‐border relations and enhance knowledge, cooperative management, and sustainability of the region's shared aquifers, stakeholders in the border between Mexico and Texas should pursue local and regional arrangements that focus primarily on water quality and environmental issues. Additionally, in order for the results of local efforts to be permanent and sustainable, they must consider the more formal, long‐term cooperative models that tend to have stronger systemic impacts and funding commitments. In addition, stakeholders and officials must make a better effort to educate the public on the science and facts in order to avoid past experiences where fear and political lobbying scuttled viable and promising cooperative efforts. This article is categorized under: Engineering Water 〉 Planning Water Human Water 〉 Water Governance

Description: This dam in LakeCounty, Montana stands 6 ft (1.83 m) tall. Abstract Most of the United States' 2.5 million dams are not under the jurisdiction of any public agency. These small (under 6 ft [1.83 m] tall) nonjurisdictional dams, unregulated and not inventoried anywhere, endanger public safety and degrade riparian ecosystems. Their problems are increasing as structures age and storm events become more violent. Property owners can be held liable for problems at dams. Through several policy changes and legal actions, states can vastly improve the situation. States should consider expanded jurisdiction over small dams, a program of inventorying and mapping all dams in state waterways, owner education and outreach, and shared resources to allow for improved public safety and river restoration through best dam management or dam removal practices. This article is categorized under: Human Water 〉 Water Governance Engineering Water 〉 Planning Water Water and Life 〉 Stresses and Pressures on Ecosystems

Description: Large wood (LW) in rivers can provide a range of benefits. This includes improving the ecological integrity of rivers, reducing flood risk and managing sediment. Numerical hydraulic and hydrological models are used to predict the effects of LW. However, the suitability of approaches to LW modeling and therefore guidance, remain uncertain. Abstract The influence of naturally occurring in‐channel large wood (LW) on the hydraulics, hydrology and geomorphology of rivers is well documented. To inform management and better understand naturally occurring or artificially placed LW, hydraulic and hydrological models are applied to predict the possible benefits and drawbacks for habitat, sediment management and flood risk mitigation. However, knowledge and guidance on appropriate representation in models, needed to underpin realistic predictions, is lacking. This could lead to unrealistic expectations of the effectiveness of LW for different river management goals. To date, seven types of LW representation in hydraulic and hydrological models have been applied, the range partly reflecting the variety of LW, model types, scales and purposes. The most common approach is by altering channel roughness to represent flow resistance. Although qualitatively the effects of LW have been captured using models, to date quantitative validation, as well as transferable knowledge to help a priori parameterization of LW representations, remain limited. Therefore, additional empirical investigations and robust model validation are required to inform defensible LW representations for specific purposes and scales in numerical models coupled with better accounting of input uncertainty to improve confidence in predictions. Future studies should also consider a greater range of artificial and natural LW features, settings, larger spatial scales and better account for temporal variability of flow, morphology and LW configuration. This article is categorized under: Water and Life 〉 Methods Science of Water 〉 Methods Water and Life 〉 Nature of Freshwater Ecosystems

Description: Wiley Interdisciplinary Reviews: Water, Volume 6, Issue 6, November/December 2019.

Description: In streams, biofilms should be depicted as ecosystem engineers as they stabilize and fertilize sediments. Their development is thus critical for river ecosystems, particularly in glacier floodplains, where sediments tend to be unstable and nutrient‐limited. Abstract The term “ecosystem engineering” emerged in the 1990s and is commonly used to refer to the activities of larger organisms like beavers and trees in rivers and streams. The focus on larger organisms may be motivated by their more visible effects on the environment. However, while it may be intuitive to suggest that the bigger the organism the bigger its potential engineering effects, there may be microscale organisms who through their number rather than their size can act simultaneously to result in significant impacts. This paper considers biofilms as a candidate ecosystem engineer. It is well known that biofilms play an important role in enriching the sediment matrix of nutrients and in stabilizing sediments. Biofilms may be critical in increasing the habitability of the benthic substratum. In this paper, we consider their potential role in the ontogeny of ecosystems in recently deglaciated terrain. We show how by changing sediment stoichiometry, decreasing sediment erodibility, and reducing surface sediment permeability they may promote primary succession on lateral, incised terraces, which are less perturbed compared with the main active floodplain. This article is categorized under: Water and Life 〉 Nature of Freshwater Ecosystems Science of Water 〉 Water and Environmental Change

Description: Transition from smooth water to extreme whitewater in House Rock Rapid, Colorado River, Grand Canyon causes high small‐scale variation in gas exchange rates ranging from low diffusive fluxes in the foreground to bubble‐mediated fluxes in the middle of the rapid. Abstract Gas exchange across the air–water boundary of streams and rivers is a globally large biogeochemical flux. Gas exchange depends on the solubility of the gas of interest, the gas concentrations of the air and water, and the gas exchange velocity (k), usually normalized to a Schmidt number of 600, referred to as k600. Gas exchange velocity is of intense research interest because it is problematic to estimate, is highly spatially variable, and has high prediction error. Theory dictates that molecular diffusivity and turbulence drives variation in k600 in flowing waters. We measure k600 via several methods from direct measures, gas tracer experiments, to modeling of diel changes in dissolved gas concentrations. Many estimates of k600 show that surface turbulence explains variation in k600 leading to predictive models based upon geomorphic and hydraulic variables. These variables include stream channel slope and stream flow velocity, the product of which, is proportional to the energy dissipation rate in streams and rivers. These empirical models provide understanding of the controls on k600, yet high residual variation in k600 show that these simple models are insufficient for predicting individual locations. The most appropriate method to estimate gas exchange depends on the scientific question along with the characteristics of the study sites. We provide a decision tree for selecting the best method to estimate k600 for individual river reaches to scaling to river networks. This article is categorized under: Water and Life 〉 Nature of Freshwater Ecosystems Science of Water 〉 Water Quality Water and Life 〉 Methods

Description: Power‐sensitive resilience of social–hydrological systems: five definitional questions with political implications derived from critiques of the resilience concept. Abstract Since the early work on defining and analyzing resilience in domains such as engineering, ecology and psychology, the concept has gained significant traction in many fields of research and practice. It has also become a very powerful justification for various policy goals in the water sector, evident in terms like flood resilience, river resilience, and water resilience. At the same time, a substantial body of literature has developed that questions the resilience concept's systems ontology, natural science roots and alleged conservatism, and criticizes resilience thinking for not addressing power issues. In this study, we review these critiques with the aim to develop a framework for power‐sensitive resilience analysis. We build on the three faces of power to conceptualize the power to define resilience. We structure our discussion of the relevant literature into five questions that need to be reflected upon when applying the resilience concept to social–hydrological systems. These questions address: (a) resilience of what, (b) resilience at what scale, (c) resilience to what, (d) resilience for what purpose, and (e) resilience for whom; and the implications of the political choices involved in defining these parameters for resilience building or analysis. Explicitly considering these questions enables making political choices explicit in order to support negotiation or contestation on how resilience is defined and used. This article is categorized under: Human Water 〉 Water Governance. Engineering Water 〉 Planning Water.

Description: Catchments are leaky units perched on a larger, regional hydrogeological system. Abstract Catchments, generally understood as the drainage areas of low‐order streams, are often regarded as closed hydrologic entities; that is, precipitation (P) minus evapotranspiration (ET) over a catchment equates stream outflow (Q r). Here, we review evidence that catchments can be leaky due to groundwater outflow or inflow across topographic divides, based on catchment mass balance across a continent and several site‐based studies across the globe. It appears that a catchment is more likely to be leaky with the combination of the following factors: small catchment size, positioned at either the high or low end of a steep regional topographic and climatic gradient, underlain by deep permeable substrates that extend beyond the study catchment, and in drier climate or dry seasons and droughts. Catchment leakage has hydrological, geochemical, and ecological implications. Thus, catchments are best framed as semiclosed hydrologic units perched on top of a larger, regional hydrogeological system with no real boundaries regarding the movement of water and solutes. This article is categorized under: Science of Water 〉 Hydrological Processes Water and Life 〉 Nature of Freshwater Ecosystems

Description: For many human populations around the world, river flows are linked to livelihood, identity, sense of place, religious beliefs and ceremonies, language systems, or educational practices. These embedded, reciprocal, and constitutive relationships between humans and rivers remain poorly understood, but can be critically important to assessment and implementation of environmental flows Abstract River flows connect people, places, and other forms of life, inspiring and sustaining diverse cultural beliefs, values, and ways of life. The concept of environmental flows provides a framework for improving understanding of relationships between river flows and people, and for supporting those that are mutually beneficial. Nevertheless, most approaches to determining environmental flows remain grounded in the biophysical sciences. The newly revised Brisbane Declaration and Global Action Agenda on Environmental Flows (2018) represents a new phase in environmental flow science and an opportunity to better consider the co‐constitution of river flows, ecosystems, and society, and to more explicitly incorporate these relationships into river management. We synthesize understanding of relationships between people and rivers as conceived under the renewed definition of environmental flows. We present case studies from Honduras, India, Canada, New Zealand, and Australia that illustrate multidisciplinary, collaborative efforts where recognizing and meeting diverse flow needs of human populations was central to establishing environmental flow recommendations. We also review a small body of literature to highlight examples of the diversity and interdependencies of human‐flow relationships—such as the linkages between river flow and human well‐being, spiritual needs, cultural identity, and sense of place—that are typically overlooked when environmental flows are assessed and negotiated. Finally, we call for scientists and water managers to recognize the diversity of ways of knowing, relating to, and utilizing rivers, and to place this recognition at the center of future environmental flow assessments. This article is categorized under: Water and Life 〉 Conservation, Management, and Awareness Human Water 〉 Water Governance Human Water 〉 Water as Imagined and Represented

Description: The connection between the weakening intensity of the terrestrial water cycle and the notion of human well‐being as a declining asset. Abstract This article develops an approach that applies macroeconomic concepts to the interpretation of complex, water related natural processes. By translating and re‐interpreting these processes into a language that is more accessible to a broader audience otherwise unaccustomed to its terms will likely help sharpen our understanding of the terrestrial water cycle. For economists, we describe climate‐forming natural processes in a manner consistent with the fundamentals of the mainstream approach. For noneconomists, parallels from economically determined, relatively short‐term observations can be applied conceptually to identify dynamics which occur over much longer and therefore more elusive natural occurrences, in particular considering the role of forests and how persistent land conversion over a millennium has shaped the earth's surface and impacted climate stability. The set of “supporting ecosystem services” highlighted in the Millennium Ecosystem Assessment (MEA) coincides with the ground phase of the terrestrial water cycle, taking the concept beyond the ecosystem service perspective and identifying it as a planetary service. Ecosystem and planetary services differ in the same way that microeconomic and macroeconomic perspectives do. The water cycle intensity of a geographical area may well be related to a rainfall multiplier that measures the ability of continental ecosystems to increase the amount of water moving across terrestrial surfaces and descending as rainfall through transpiration and deposition, and re‐transpiration and re‐deposition of the water content in the air that originally arrives from the oceans. Building upon the MEA's association of human wellbeing with ecosystem features, the rainfall multiplier serves as a physical indicator and measure of the natural basis of wellbeing creation. This article is categorized under: Human Water 〉 Water as Imagined and Represented Water and Life 〉 Conservation, Management, and Awareness Human Water 〉 Value of Water

Description: Managerial‐focused approaches to groundwater governance have not succeeded to improve the situation of the resource and fail to reconcile the fundamental dynamics of groundwater as a resource and governance as a sociopolitical phenomenon. As a result, solutions based on these existing approaches remain partial at best. Abstract With decreasing aquifer levels, increasing groundwater pollution, inequitable access, and generally poor management outcomes, better groundwater governance has been put forward as a recipe to address these challenges worldwide. Existing recommendations focus on improved legal frameworks, monitoring and control of access and abstraction through permits or formal rights. In addition, decentralized water management, enforcement of regulations, and supply‐side technological solutions are seen as cornerstone components of good groundwater governance systems. However, until now, these approaches have generally failed to reconcile the fundamental dynamics and properties of groundwater as a natural resource and of governance as a social and political phenomenon. This has caused a disregard for local to planetary boundaries, power dynamics, and intra‐ and intergenerational inequalities in access to benefits from groundwater. As the current general notion of good groundwater governance is limited, solutions put forward are also partial and do not encompass the wider challenges affecting groundwater governance, in effect replacing sustainable management goals and policy for governance as a process. This paper takes a particular look at the Middle East and North Africa and agricultural groundwater use for irrigation to constructively redefine groundwater governance and fully address the multilayered and multifaceted core challenges of groundwater governance. Equally, the paper puts forward a new conceptual thinking that will help support the effective development of governance‐based solutions to achieve sustainable, socially acceptable, resilient and equitable resource use. This article is categorized under: Engineering Water 〉 Planning Water Human Water 〉 Water Governance

Description: In times of climate change, our cities have to deal with heavy rainfall events and risks of pluvial flooding, as occurred in the city of Kaiserslautern (Germany) on June 11, 2018—in fact a great and urgent common task for all local actors towards more resilient cities. Image: Theo Schmitt (2018). Abstract The increase of pluvial flooding has long been discussed to be a most probable outcome of climate change. This has raised the question of necessary consequences in the design of urban drainage systems in order to secure adequate flood protection and resilience. Due to the uncertainties in future trends of heavy rainfall events, the awareness of remaining risks of extreme pluvial flooding needs to be roused at responsible decision makers and the public as well leading to the implementation of pluvial flood risk management (PFRM) concepts. The state of two core elements of PFRM in Germany are described here: flood hazard and risk evaluation and risk communication. In 2016 the guideline DWA‐M 119 has been published to establish city‐based PFRM concepts in specification of the European Flood Risk Management Directive (EU 2007). As core elements, the guidelines recommend a site‐specific analysis and evaluation of flood hazards and potentials of flood damages to create flood hazard and flood risk maps. In the long run, PFRM needs to be established as a joint community effort and a requirement for more flood resilience. The risk communication within the administration and in the public requires a comprehensible characterization and classification of heavy rainfall to illustrate event extremity. The concept of a rainstorm severity index (RSI) instead of statistical rainfall parameters appears to be promising to gain a better perception by affected citizens and non‐hydrology‐experts as well. A methodical approach is described to specify and assign site‐specific rainfall depths within the severity index scheme RSI12. This article is categorized under: Engineering Water 〉 Sustainable Engineering of Water Engineering Water 〉 Planning Water Engineering Water 〉 Methods

Description: Approaches to develop optimal operating rules Abstract Coordinated and efficient operation of water resource systems becomes essential to deal with growing demands and uncertain resources in water‐stressed regions. System analysis models and tools help address the complexities of multireservoir systems when defining operating rules. This paper reviews the state of the art in developing operating rules for multireservoir water resource systems, focusing on efficient system operation. This review focuses on how optimal operating rules can be derived and represented. Advantages and drawbacks of each approach are discussed. Major approaches to derive optimal operating rules include direct optimization of reservoir operation, embedding conditional operating rules in simulation‐optimization frameworks, and inferring rules from optimization results. Suggestions on which approach to use depend on context. Parametrization–simulation–optimization or rule inference using heuristics are promising approaches. Increased forecasting capabilities will further benefit the use of model predictive control algorithms to improve system operation. This article is categorized under: Engineering Water 〉 Water, Health, and Sanitation Engineering Water 〉 Methods

Description: Groundwater comanagement: a continuum. Abstract The sustainability of groundwater abstraction is fast becoming a global challenge. This article reviews cases and assess the potential of groundwater comanagement, beginning by identifying a comanagement spectrum with varying degrees of role sharing between the state and user communities. Twelve case studies selected from a global review illustrate varied levels of success. Key contextual elements are identified that contribute to raising the chances of success of comanagement. These include certain characteristics of the user community, the existence of a credible environmental or legal threat, joint monitoring and transparency, and substantial available funding. State action is shown to involve a delicate balance between “carrots” and “sticks” as part of a wider political balancing between parties. The limitations of both state‐ and community‐centered governance make comanagement appear as a way forward but a delicate set of conditions is needed for it to be effective. This article is categorized under: Human Water 〉 Water Governance Engineering Water 〉 Planning Water