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981.
982.
James E.T. Moncur 《Journal of the American Water Resources Association》1989,25(3):499-505
ABSTRACT: Municipal water utilities, when faced with drought conditions, typically impose a temporary water use restrictions program to achieve conservation goals. If water is sufficiently price-elastic, however, at least some of the problems associated with restrictions can be avoided by imposing a drought surcharge and allowing users to adjust voluntarily. This paper develops two sources of evidence on price elasticity in Honolulu, Hawaii, with the evidence suggesting that a drought surcharge will induce much of the desired conservation, especially when used with educational publicity. 相似文献
983.
The couplings among chemical reaction rates, advective and diffusive transport in fractured media or soils, and changes in hydraulic properties due to precipitation and dissolution within fractures and in rock matrix are important for both nuclear waste disposal and remediation of contaminated sites. This paper describes the development and application of LEHGC2.0, a mechanistically based numerical model for simulation of coupled fluid flow and reactive chemical transport, including both fast and slow reactions in variably saturated media. Theoretical bases and numerical implementations are summarized, and two example problems are demonstrated. The first example deals with the effect of precipitation/dissolution on fluid flow and matrix diffusion in a two-dimensional fractured media. Because of the precipitation and decreased diffusion of solute from the fracture into the matrix, retardation in the fractured medium is not as large as the case wherein interactions between chemical reactions and transport are not considered. The second example focuses on a complicated but realistic advective-dispersive-reactive transport problem. This example exemplifies the need for innovative numerical algorithms to solve problems involving stiff geochemical reactions. 相似文献
984.
Ingrid M. Tohver Alan F. Hamlet Se‐Yeun Lee 《Journal of the American Water Resources Association》2014,50(6):1461-1476
Climate change projections for the Pacific Northwest (PNW) region of North America include warmer temperatures (T), reduced precipitation (P) in summer months, and increased P during all other seasons. Using a physically based hydrologic model and an ensemble of statistically downscaled global climate model scenarios produced by the Columbia Basin Climate Change Scenarios Project, we examine the nature of changing hydrologic extremes (floods and low flows) under natural conditions for about 300 river locations in the PNW. The combination of warming, and shifts in seasonal P regimes, results in increased flooding and more intense low flows for most of the basins in the PNW. Flood responses depend on average midwinter T and basin type. Mixed rain and snow basins, with average winter temperatures near freezing, typically show the largest increases in flood risk because of the combined effects of warming (increasing contributing basin area) and more winter P. Decreases in low flows are driven by loss of snowpack, drier summers, and increasing evapotranspiration in the simulations. Energy‐limited basins on the west side of the Cascades show the strongest declines in low flows, whereas more arid, water‐limited basins on the east side of the Cascades show smaller reductions in low flows. A fine‐scale analysis of hydrologic extremes over the Olympic Peninsula echoes the results for the larger rivers discussed above, but provides additional detail about topographic gradients. 相似文献
985.
986.
Emmet M. Owens Steven W. Effler David M. O'Donnell David A. Matthews 《Journal of the American Water Resources Association》2014,50(1):205-218
The transport and fate of two plunging tributaries, Onondaga and Ninemile Creeks, in Onondaga Lake, New York, are quantified based on application of hydrodynamic/transport models. Short‐term transport is simulated with a three‐dimensional Estuary Lake and Coastal Ocean Model (ELCOM), while the longer term fate is represented by a previously validated one‐dimensional model (UFILS4). The validation of ELCOM for the vertical distribution of tributary inflow into the lake's water column is demonstrated for four dye tracer experiments. The models are applied for three years to represent the dynamics of transport and fate for the two tributaries, with ELCOM predictions serving as input for UFILS4. The models together quantify the distribution of these inflows between the upper mixed layer (UML) and stratified depths, and the subsequent transport from stratified depths to the UML by vertical mixing. Substantial short‐term variations are predicted for both tributaries in response to variability in hydrology and weather. Increased inflow to the UML is predicted for high runoff periods. The fraction of Ninemile Creek's inflow directly entering the UML is predicted to be 50% greater than for Onondaga Creek due to Ninemile's lower negative buoyancy. The plunging phenomenon has important water quality implications, by reducing the effective loading to the UML, particularly for constituents with large rates of loss/transformation relative to the rate of vertical transport from stratified depths. 相似文献
987.
依据京杭运河常州段河网水量水质同步监测数据,建立常州河网区水量水质数学模型,应用该模型对京杭运河常州段改线后水环境改善方案进行分析计算,京杭运河常州段通过引水可改善水质,但若要保持水质基本达到Ⅳ类水质标准,研究显示该区域在第三种截污情况下,需由上游新孟河和德胜河调引长江水50m3/s。 相似文献
988.
Jurgen D. Garbrecht Jeanne M. Schneider Michael W. Van Liew 《Journal of the American Water Resources Association》2006,42(5):1285-1295
ABSTRACT: Conditions under which monthly rainfall forecasts translate into monthly runoff predictions that could support water resources planning and management activities were investigated on a small watershed in central Oklahoma. Runoff response to rainfall forecasts was simulated using the hydrologic model SWAT. Eighteen scenarios were examined that represented combinations of wet, average, and dry antecedent rainfall conditions, with wet, normal, and dry forecasted rainfall. Results suggest that for the climatic and physiographic conditions under consideration, rainfall forecasts could offer potential application opportunities in surface water resources but only under certain conditions. Pronounced wet and dry antecedent rainfall conditions were shown to have greater impact on runoff than forecasts, particularly in the first month of a forecast period. Large forecast impacts on runoff occurred under wet antecedent conditions, when the fraction of forecasted rainfall contributing to runoff was greatest. Under dry antecedent conditions, most of the forecasted rainfall was absorbed in the soil profile, with little immediate runoff response. Persistent three‐month forecasts produced stronger impacts on runoff than one‐month forecasts due to cumulative effects in the hydrologic system. Runoff response to antecedent conditions and forecasts suggest a highly asymmetric utility function for rainfall forecasts, with greatest decision‐support potential for persistent wet forecasts under wet antecedent conditions when the forecast signal is least dampened by soil‐storage effects. Under average and dry antecedent conditions, rainfall forecasts showed little potential value for practical applications in surface water resources assessments. 相似文献
989.
Éric Wajnberg 《Behavioral ecology and sociobiology》2006,60(5):589-611
As most parasitoids are time limited, they usually die before they have laid all their eggs. In such cases, optimal foraging theory predicts that female parasitoids will adopt behavioral reproductive strategies enabling them to maximize progeny production per unit of time. One key situation in which parasitoid females must optimize their time budget is related to the fact that most of their hosts are distributed in discrete patches in the environment. In this review, I first present the results of basic theoretical models predicting female wasp search duration on a patch of hosts. I then compile and analyze all studies investigating the effect of different factors on parasitoid patch time allocation and patch-leaving decision rules. Different patch-leaving mechanisms that were proposed to explain the results obtained are discussed, along with statistical methods that should be used to estimate them from experimental data. Finally, ideas for future research are presented. 相似文献
990.