ALBERT

Notes: : This paper reports on new methods of linking climate change scenarios with hydrologic, agricultural an water planning models to study future water availability for agriculture, an essential element of sustainability. The study is based on the integration of models of water supply and demand, and of crop growth and irrigation management. Consistent modeling assumptions, available databases, and scenario simulations are used to capture a range of possible future conditions. The linked models include WATBAL for water supply; CERES, SOYGRO, and CROPWAT for crop and irrigation modeling; and WEAP for water demand forecasting, planning and evaluation. These models are applied to the U.S. Cornbelt using forecasts of climate change, agricultural production, population and GDP growth.Results suggest that, at least in the near term, the relative abundance of water for agriculture can be maintained under climate change conditions. However, increased water demands from urban growth, increases in reservoir evaporation and increases in crop consumptive use must be accommodated by timely improvements in crop, irrigation and drainage technology, water management, and institutions. These improvements are likely to require substantial resources and expertise. In the highly irrigated basins of the region, irrigation demand greatly exceeds industrial and municipal demands. When improvements in irrigation efficiency are tested, these basins respond by reducing demand and lessening environmental stress with an improvement in system reliability, effects particularly evident under a high technology scenario. Rain-fed lands in the Cornbelt are not forced to invest in irrigation, but there is some concern about increased water-logging during the spring and consequent required increased investment in agricultural drainage. One major water region in the Cornbelt also provides a useful caveat: change will not necessarily be continuous and monotonic. Under one GCM scenario for the 2010s, the region shows a significant decrease in system reliability, while the scenario for the 2020s shows an increase.

Notes: Field surveys of Thames Water's distribution mains found the occurrence of ‘red water’ to be highly variable and localized. To model the many inter-related factors identified in the field, a controlled pipeline-testing facility was required to simulate conditions in a ‘live’ network, but on a pilot-scale. This was achieved by incorporating a specialized red-water testing facility into an existing experimental pipeline.This paper describes the hydraulic and material design features, including the addition of a ‘dead-end’ section operated on a stagnation and flow regime, quantified using computational fluid dynamics. Following commissioning, the facility has provided detailed, time-sequenced observations on corrosion-deposit development and red-water generation under different hydraulic regimes.

Notes: The enumeration of heterotrophic bacteria is an important measure of water quality in mains’distribution systems. Conventional methods of enumerating bacteria by plate counts do not distinguish between single bacteria and clumps of cells; however, various methods have been reported which use epifluorescence microscopy to give a direct count of bacteria. There appears to be no standard method for the preparation of samples, with the choice of fluorochrome and staining technique varying considerably – even between workers using similar environmental samples. A number of the reported methods were tested, and a technique was developed which enabled a consistent total count of bacterial cells (occurring both singularly and in clumps) to be obtained.

Notes: We use the spatial distribution of moment tensors of earthquakes in this century to estimate the velocity field in Asia within a Eurasian reference frame. In a least-squares inversion, strain rates on the surface of the Earth are matched with continuous spline functions in order to recover the velocity gradient tensor associated with the seismic moment release in Asia. Earthquakes account for 40–60 per cent of the expected motion of India relative to Eurasia, with the missing component of strain rate equivalent to about 20 mm yr−1 of N-S shortening between Siberia and India. In this solution, South China rotates counterclockwise and moves eastwards relative to Siberia.Using rigid plate constraints, we next investigate the characteristics of the complete horizontal strain field in Asia that accommodates plate motions. Our strain-rate solutions are analogous to the response of a Newtonian thin viscous sheet in which the rate of work done by the straining medium in accommodating the velocity boundary conditions is a minimum. In these solutions the Euler pole for India relative to Eurasia is constrained (NUVEL-1A; DeMets et al. 1994), but in the process of fitting the VLBI velocity at Shanghai, China (Ward 1994; Heki et al. 1995), the Euler pole for South China is determined in the inversion. A solution that both fits the velocity at Shanghai, China and yields a strain-rate field consistent with the earthquake mechanisms is one where the South China block has a motion relative to Siberia described by the pole at (51°N, 131°E, 0.3 deg Myr−1).Comparison of the complete strain field that accommodates plate motion with the seismic strains indicates that earthquake moment release rates in this century within Mongolia are about a factor of 4 larger than the long-term rate. Within Gansu-Ningxia, the earthquake moment rates have been about a factor of 2 higher than the long-term rate. The strike-slip faulting within Mongolia, Gansu-Ningxia, western Sichuan and Yunnan is possibly a direct result of velocity boundary conditions imposed on the South China block by forces unrelated to continental collision of India and Eurasia, such as forces associated with subduction along the margins of South-eastern Asia. Verification of this requires a better understanding of the role of pre-existing zones of weakness within the Asian continental lithosphere.

Notes: In this paper we attempt to apply techniques that have recently been developed to describe distributed deformation on the continents to distributed deformation in subducting lithosphere slabs. We chose a part of the Tonga slab for this study because it has a simple, approximately planar, shape and high seismicity. We then used the spatial distribution of seismic strain rates, based on earthquake centroid-moment-tensor solutions in the interval 1977-1994, to recover a velocity field that describes the seismic deformation in the plane of the slab below a depth of 100 km. Between 100 and ˜450 km depth the seismic deformation is dominated by down-dip shortening and slab thickening. Below ˜450 km the down-dip shortening seen in the earthquakes is still important, but it is absorbed roughly equally by along-strike extension and by thickening. There is little evidence of along-strike shear at depth. We have more confidence in the pattern of strain rates and velocities that we obtain than in their absolute values. Nevertheless, the rates of down-dip shortening accounted for by seismicity are probably less than half those needed if the whole down-dip component of Pacific-Australia plate convergence is absorbed by shortening in the upper mantle. The style of deformation at the base of the slab is complex and, unlike many regions of distributed continental tectonics, is not easily represented by simple patterns of faulting.

Notes: Pennisetum clandestinum Hochst ex Chiov. (kikuyugrass) is a C4 grass that has become an invasive weed in temperate climates. We examined ecophysiological mechanisms that have allowed it to become a successful weed in these locations by comparing P. clandestinum and two other common turigrass species, Festuca arundinacea Schreb. (tall fescue cv. Mojave), a C3 cool-season grass, and Stenotaphrum secundatum (Walt.) Kuntze (St. Augustinegrass), a C4 warm-season grass, grown in a warm or cool growth regime. We measured rates of photosynthesis over a range of leaf temperatures and also measured growth rate parameters of these species. At leaf temperatures between 25^C and 40^C P. clandestinum maintained the highest rates of photosynthesis in both temperature regimes. Under warm temperatures, this species rapidly increased biomass and leaf area to a greater extent than either of the other two grasses. Theoretical whole plant photosynthesis (mean leaf area × mean photosynthetic rate) was higher for P. clandestinum than for the other two species in both growth regimes and over most leaf temperatures. Our results suggest that P. clandestinum is a successful weed in Mediterranean climates as a result of its capacity to photosynthesize over the full range of temperatures found in those climates, its rapid growth during warm weather and its apparent tolerance to moderately cool temperatures.