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  • 1
    Publication Date: 2019-07-08
    Description: Hydromorphological attributes such as flow width, water extent, and gradient play an important role in river hydrological, biogeochemical, and ecological processes and can help to predict river conveyance capacity, discharge, and flow routing. While there are some river width datasets at global or regional scales, they do not consider temporal variation in river width and do not cover all Australian rivers. We combined detailed mapping of 1.4 million river reaches across the Australian continent with inundation frequency mapping from 27 years of Landsat observations. From these, the average flow width at different recurrence frequencies was calculated for all reaches, having a combined length of 3.3 million km. A parameter γ was proposed to describe the shape of the frequency–width relationship and can be used to classify reaches by the degree to which flow regime tends towards permanent, frequent, intermittent, or ephemeral. Conventional scaling rules relating river width to gradient and contributing catchment area and discharge were investigated, demonstrating that such rules capture relatively little of the real-world variability. Uncertainties mainly occur in multi-channel reaches and reaches with unconnected water bodies. The calculated reach attributes are easily combined with the river vector data in a GIS, which should be useful for research and practical applications such as water resource management, aquatic habitat enhancement, and river engineering and management. The dataset is available at https://doi.org/10.25914/5c637a7449353 (Hou et al., 2019).
    Print ISSN: 1866-3508
    Electronic ISSN: 1866-3516
    Topics: Geosciences
    Published by Copernicus
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  • 2
    Publication Date: 2018-05-31
    Description: River discharge measurements have proven invaluable to monitor the global water cycle, assess flood risk, and guide water resource management. However, there is a delay and overall decline in the availability of gauging data and stations are highly unevenly distributed globally. While not a substitute for river discharge measurement, remote sensing is a cost-effective technology to acquire information on river dynamics. The general approach has been to relate satellite observation to discharge measured in situ, which prevents its use for ungauged rivers. Alternatively, hydrological models are now available that can be used to estimate river discharge globally. While subject to greater errors and biases than measurements, model estimates of river discharge do expand the options for applying satellite-based discharge monitoring in ungauged rivers. Our aim was to test this approach. We used gridded surface water extent information from two sources: (1) Global Flood Detection System (GFDS) passive microwave data; and (2) MODIS optical data. The data were available for the common period of 2000–2014. The hydrological model used was the World-Wide Water (W3) model version 2, providing river discharge from 1980 to 2014. We designed and compared two methods to relate simulated storage and discharge to MODIS and GFDS surface water extent fraction for developing satellite gauging reaches (SGRs), and applied the best performing method to construct SGRs across the Amazon Basin. River discharge estimates from MODIS SGRs, GFDS SGRs, and the W3 model were evaluated with in situ river discharge measurements. The results showed SGRs can be successfully established over a large area using MODIS and GFDS water extent and modelled discharge, and used to estimate river discharge at both gauged and ungauged sites.
    Print ISSN: 1812-2108
    Electronic ISSN: 1812-2116
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union (EGU).
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  • 3
    Publication Date: 2019-02-20
    Description: Hydromorphological attributes such as flow width, water extent and gradient play an important role in river hydrological, biogeochemical and ecological processes; helping to predict river conveyance capacity, discharge and flow routing. While there are some river width datasets at global or regional scales, they do not consider temporal variation in river width and do not cover all Australian rivers. We combined detailed mapping of 1.4 million river reaches across the Australian continent with inundation frequency mapping from 27-years of Landsat observations. From these, the average flow width at different recurrence frequencies was calculated for all reaches, having a combined length of 3.3 million km. A parameter γ was proposed to describe the shape of the frequency-width relationship and can be used to classify reaches by the degree to which flow regime tends towards permanent, frequent, intermittent or ephemeral. Proposed scaling rules relating river width to gradient and contributing catchment area and discharge were investigated, demonstrating that such rules capture relatively little of real-world variability. Uncertainties mainly occur in multi-channel reaches and reaches with unconnected water bodies. The calculated reach attributes are easily combined with the river vector data in GIS, which should be useful for research and practical applications such as water resource management, aquatic habitat enhancement, and river engineering and management. The dataset is available at https://doi.org/10.25914/5c637a7449353 (Hou et al. 2019).
    Electronic ISSN: 1866-3591
    Topics: Geosciences
    Published by Copernicus
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  • 4
    Publication Date: 2018-12-11
    Description: River discharge measurements have proven invaluable to monitor the global water cycle, assess flood risk, and guide water resource management. However, there is a delay, and ongoing decline, in the availability of gauging data and stations are highly unevenly distributed globally. While not a substitute for river discharge measurement, remote sensing is a cost-effective technology to acquire information on river dynamics in situations where ground-based measurements are unavailable. The general approach has been to relate satellite observation to discharge measured in situ, which prevents its use for ungauged rivers. Alternatively, hydrological models are now available that can be used to estimate river discharge globally. While subject to greater errors and biases than measurements, model estimates of river discharge do expand the options for applying satellite-based discharge monitoring in ungauged rivers. Our aim was to test whether satellite gauging reaches (SGRs), similar to virtual stations in satellite altimetry, can be constructed based on Moderate Resolution Imaging Spectroradiometer (MODIS) optical or Global Flood Detection System (GFDS) passive microwave-derived surface water extent fraction and simulated discharge from the World-Wide Water (W3) model version 2. We designed and tested two methods to develop SGRs across the Amazon Basin and found that the optimal grid cell selection method performed best for relating MODIS and GFDS water extent to simulated discharge. The number of potential river reaches to develop SGRs increases from upstream to downstream reaches as rivers widen. MODIS SGRs are feasible for more river reaches than GFDS SGRs due to its higher spatial resolution. However, where they could be constructed, GFDS SGRs predicted discharge more accurately as observations were less affected by cloud and vegetation. We conclude that SGRs are suitable for automated large-scale application and offer a possibility to predict river discharge variations from satellite observations alone, for both gauged and ungauged rivers.
    Print ISSN: 1027-5606
    Electronic ISSN: 1607-7938
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union (EGU).
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  • 5
    Publication Date: 2001-04-01
    Print ISSN: 0378-1127
    Electronic ISSN: 1872-7042
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Elsevier
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  • 6
    Publication Date: 1990-07-01
    Description: The heat pulse method was used to estimate stand transpiration from a radiata pine (Pinus radiata) plantation in southeastern Australia over a period of four days. The diurnal pattern of sapflow was related to net radiation with a time lag of about 1.5 hours. Despite high soil moisture levels, sapflow did not keep up with evaporative demand in the afternoon. Sapflow estimates of transpiration exceeded estimates for evaporation based on Bowen ratio measurements for all four days of the study. Copyright © 1990 John Wiley & Sons, Ltd
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 7
    Publication Date: 1998-05-01
    Description: A large-scale distribution function model was used to investigate the effect of differing parameter mapping schemes on the quality of hydrological predictions. Precipitation was mapped over a large forested catchment area (163 km2) using both one-dimensional linear and three-dimensional non-linear interpolation schemes. Lumped stream flow predictions were found to be particularly sensitive to the different precipitation maps, with the three-dimensional map predicting 12% higher mean annual precipitation, resulting in 36% higher modelled stream flow over a three-yr period. However, spatial predictions of stream flow appeared worse when derived from the three-dimensional map, which is considered the better of the two precipitation maps. This implies uncertainty in either the model's response to precipitation or the precipitation mapping process (the 12% precipitation difference was strongly determined by a single, short term gauge). Leaf area index (LAI) was mapped using both remote sensing and species based methods. The two LAI maps had similar lumped mean values but exhibited significant spatial differences. The resulting lumped predictions of stream flow did not vary. This suggests a linear response of water balance to LAI in the non-water-limited conditions of the study area, and de-emphasizes the importance of quanitfying relative spatial variations in LAI. Topographic maps were created for a small experimental subcatchment (15 ha) using both air photographic interpretation and ground survey. The two maps differed markedly and lead to significantly different spatial predictions of runoff generation, but nearly identical predicted hdyrographs. Thus, at scales of small basins accurate topographic mapping is suggested to be of little importance indistribution function modelling because models are unable to make use of complex spatial data. Predictions of water yield can be very sensitive (in the case of precipitation) or insensitive (in the case of small-scale topography) to changes in spatial parameterization. In either case, increased complexity in spatial parameterization does not necessarily result in better, or more certain prediction of hydrological response.The effect of differing parameter mapping schemes on the quality of hydrological predictions was investigated using a large-scale distribution function model. Precipitation was mapped over a large forested catchment area using one-dimensional linear and three-dimensional nonlinear interpolation schemes. Lumped stream flow predictions were found to be particularly sensitive to the different precipitation maps. Leaf area index was mapped by remote sensing and species-based method. The two maps differed markedly, and lead to significantly-different spatial predictions of runoff generation, but nearly identical predicted hydrographs.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 8
    Publication Date: 1999-04-15
    Description: Most studies on the use of physically based hydrological models have identified saturated hydraulic conductivity (K(sat)) as one of the most sensitive input parameters. However, K(sat) is also one of the most difficult landscape properties to measure accurately, casting doubt on the ability of modellers to estimate this parameter a priori for catchment simulations. Several studies have shown that K(sat) estimates are greatly influenced by the measurement method used, primarily because of scale effects. In this paper, we evaluate the effect of K(sat) measurement method on catchment simulations aimed at predicting water yield from forested catchments. A series of simulations are conducted using the Topog_Dynamic catchment model, with K(sat) estimated by means of the constant head well permeameter, small core (6.3 cm x 7.3 cm) and large core (22.3 cm x 30 cm) methods. These were applied in a deep, permeable forest soil in which macropore flow has been noted to occur. The three measurement methods yielded very different K(sat) estimates and these had a large effect on model results. The model predictions based on small core and well permeameter measurements were extremely poor, as these methods did not adequately account for preferential flow through the soil. The large core estimates of K(sat), which were one to three orders of magnitude higher than the values obtained by the other two techniques, produced good predictions of catchment discharge and known spatial patterns of water table depth. Our results highlight the need for caution when applying soil hydraulic measurements to catchment-scale models.Most studies on the use of physically based hydrological models have identified saturated hydraulic conductivity (Ksat) as one of the most sensitive input parameters. However, Ksat is also one of the most difficult landscape properties to measure accurately, casting doubt on the ability of modellers to estimate this parameter a priori for catchment simulations. Several studies have shown that Ksat estimates are greatly influenced by the measurement method used, primarily because of scale effects. In this paper, we evaluate the effect of Ksat measurement method on catchment simulations aimed at predicting water yield from forested catchments. A series of simulations are conducted using the Topog_Dynamic catchment model, with Ksat estimated by means of the constant head well permeameter, small core (6.3 cm×7.3 cm) and large core (22.3 cm×30 cm) methods. These were applied in a deep, permeable forest soil in which macropore flow has been noted to occur. The three measurement methods yielded very different Ksat estimates and these had a large effect on model results. The model predictions based on small core and well permeameter measurements were extremely poor, as these methods did not adequately account for preferential flow through the soil. The large core estimates of Ksat, which were one to three orders of magnitude higher than the values obtained by the other two techniques, produced good predictions of catchment discharge and known spatial patterns of water table depth. Our results highlight the need for caution when applying soil hydraulic measurements to catchment-scale models.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 9
    Publication Date: 2000-01-01
    Description: The Amazon basin covers an area of roughly 7 x 106 km2 and encompasses diverse soil-landscape types with potentially differing hydrological behaviour. This study was conducted in the Ultisol landscape of the western Amazon basin in Peru. Processes of stormflow generation were investigated on an event basis in a first-order rainforest catchment to establish a causal link between soil physical and precipitation characteristics, hillslope flowpaths and stormflow hydrograph attributes. A sharp decrease in soil hydraulic conductivity with depth and high rainfall intensity and frequency favour rapid near-surface flowpaths, mainly in the form of saturation-excess overland flow and return flow. The latter results in an almost random occurrence of overland flow, with no obvious topographic control. Hillslope flowpaths do not vary much with respect to the hydrograph attributes time of rise, response time, lag time and centroid lag time. They have the same response time as streamflow, but a somewhat lower time of rise and significantly shorter lag times. The recession constant for hillslope hydrographs is about 10 min, in contrast to the streamflow recession constants of 28, 75 and 149 min. Stormflow generation in this Ultisol rainforest catchment differs strongly from that reported for Oxisol rainforest catchments. These two soilscapes may define a spectrum of possible catchment hydrological behaviour in the Amazon basin. Copyright (C) 2000 John Wiley and Sons, Ltd.The Amazon basin covers an area of roughly 7×106 km2 and encompasses diverse soil-landscape types with potentially differing hydrological behaviour. This study was conducted in the Ultisol landscape of the western Amazon basin in Peru. Processes of stormflow generation were investigated on an event basis in a first-order rainforest catchment to establish a causal link between soil physical and precipitation characteristics, hillslope flowpaths and stormflow hydrograph attributes. A sharp decrease in soil hydraulic conductivity with depth and high rainfall intensity and frequency favour rapid near-surface flowpaths, mainly in the form of saturation-excess overland flow and return flow. The latter results in an almost random occurrence of overland flow, with no obvious topographic control. Hillslope flowpaths do not vary much with respect to the hydrograph attributes time of rise, response time, lag time and centroid lag time. They have the same response time as streamflow, but a somewhat lower time of rise and significantly shorter lag times. The recession constant for hillslope hydrographs is about 10 min, in contrast to the streamflow recession constants of 28, 75 and 149 min. Stormflow generation in this Ultisol rainforest catchment differs strongly from that reported for Oxisol rainforest catchments. These two soilscapes may define a spectrum of possible catchment hydrological behaviour in the Amazon basin.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 10
    Publication Date: 1999-04-15
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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