GROUND-WATER RECHARGE THROUGH ACTWE SAND DUNES IN NORTHWESTERN NEVADA1

ABSTRACT: Most water-resouree investigations in semiarid basins of the Great Basin in western North America conclude that ground-water recharge from direct precipitation on the valley floor is negligible. However, many of these basins contain large areas covered by unvegetated, active sand dunes that may act as conduits for ground-water recharge. The potential for this previously undocumented recharge was investigated in an area covered by sand dunes in Desert Valley, northwestern Nevada, using a deep percolation model. The model uses daily measurements of precipitation and temperature th determine energy and moisture balances, from which estimates of long-term mean annual recharge are made. For the study area, the model calculated a mean annual recharge rate of as much as 1.3 inches per year, or 17 percent of the long-term mean precipitation. Model simulations also indicate that recharge would be virtually zero if the study area were covered by vegetation rather than dunes.     

Physical and Temporal Isolation of Mountain Headwater Streams in the Western Mojave Desert,Southern California1

Abstract: Streams draining mountain headwater areas of the western Mojave Desert are commonly physically isolated from downstream hydrologic systems such as springs, playa lakes, wetlands, or larger streams and rivers by stream reaches that are dry much of the time. The physical isolation of surface flow in these streams may be broken for brief periods after rainfall or snowmelt when runoff is sufficient to allow flow along the entire stream reach. Despite the physical isolation of surface flow in these streams, they are an integral part of the hydrologic cycle. Water infiltrated from headwater streams moves through the unsaturated zone to recharge the underlying ground‐water system and eventually discharges to support springs, streamflow, isolated wetlands, or native vegetation. Water movement through thick unsaturated zones may require several hundred years and subsequent movement through the underlying ground‐water systems may require many thousands of years – contributing to the temporal isolation of mountain headwater streams.     

Use of Streamflow Data to Estimate Base Flow/Ground‐Water Recharge For Wisconsin1

Abstract: The average annual base flow/recharge was determined for streamflow‐gaging stations throughout Wisconsin by base‐flow separation. A map of the State was prepared that shows the average annual base flow for the period 1970‐99 for watersheds at 118 gaging stations. Trend analysis was performed on 22 of the 118 streamflow‐gaging stations that had long‐term records, unregulated flow, and provided aerial coverage of the State. The analysis found that a statistically significant increasing trend was occurring for watersheds where the primary land use was agriculture. Most gaging stations where the land cover was forest had no significant trend. A method to estimate the average annual base flow at ungaged sites was developed by multiple‐regression analysis using basin characteristics. The equation with the lowest standard error of estimate, 9.5%, has drainage area, soil infiltration and base flow factor as independent variables. To determine the average annual base flow for smaller watersheds, estimates were made at low‐flow partial‐record stations in 3 of the 12 major river basins in Wisconsin. Regression equations were developed for each of the three major river basins using basin characteristics. Drainage area, soil infiltration, basin storage and base‐flow factor were the independent variables in the regression equations with the lowest standard error of estimate. The standard error of estimate ranged from 17% to 52% for the three river basins.     

COMPARATIVE EVALUATION OF THREE URBAN RUNOFF MODELS1

ABSTRACT: Three urban runoff models, namely, the Road Research Laboratory Model (RRLM), the Storm Water Management Model (SWMM) and the University of Cincinnati Urban Runoff Model (UCURM), were examined by comparing the model simulated hydrographs with the hydrographs measured on several instrumented urban watersheds. This comparison was done for the hydrograph peak points as well as for the entire hydrographs using such statistical measures as the correlation coefficient, the special correlation coefficient and the integral square error. The results of the study indicated that, when applying the three selected non-calibrated models on small urban catchments, the SWM model performed marginally better than the RRL model and both these models were more accurate than the UCUR model. On larger watersheds, the comparisons between the SWM model and the other two models would be likely even more favourable for the SWM model, because it has the most advanced flow routing scheme among the studied models.     

下凹式绿地在降雨径流控制中的应用研究

下凹式绿地具有蓄渗雨水、削减洪峰流量、净化雨水、防止土壤侵蚀等优点,且投资少,是一种能同时满足环境、生态、经济等多重效应的新型雨水利用措施;它的应用将有效缓解城市水资源匮乏和降雨地表径流造成的面源污染,同时能在一定程度上防止城市内涝.在介绍下凹式绿地对降雨径流控制的基础上,着重综述了下凹式绿地对雨水的蓄渗、净化作用及其设计方面的研究进展.     

Vegetation and carbon sequestration and their relation to water resources in an inland river basin of Northwest China

In the Heihe River Basin in the arid inland area of northwest China, the distribution of water resources in vegetation landscape zones controls the ecosystems. The carbon sequestration capacity of vegetation is analyzed in relation to water resources and vegetation growing conditions. During the last 20 years, the vegetation ecosystems have degenerated in the Heihe River Basin. Simulation using the C-FIX model indicates that, at present, the total amount of NPP of vegetation accounts for about 18.16 TgC, and the average value is 106 gC/m(2)/yr over the whole basin. NPP has generally the highest value in the upperstream mountain area, middlestream artificial oases area, downstream river bank area, alluvial fan and the terminal lake depression where vegetation grows relatively well. The lowest value is found in the vast downstream desert and Gobi area. Protection of vegetation ecosystems and enhancement of carbon sequestration require such inland river basins as the Heihe River Basin to be brought under management in a comprehensive way, taking water as a key, to carry out a rational and efficient allocation and utilization of water resources.     

高速公路路面雨水径流下渗系统性能研究

为了分析径流下渗系统在径流削减和污染控制方面的性能,本文对一个高速公路路面雨水径流下渗系统性进行了监测.结果表明,降雨量、径流量、径流削减量和径流排放量之间存在明显的正相关性(r=0.82～0.97,p0.05).该系统表现出高效的径流削减能力,当降雨量小于20 mm时,可以削减70%以上的径流量.与径流削减相比,该系统在污染物负荷控制方面更为有效.当降雨量在0～10 mm之间时,污染负荷的削减率几乎为100%;而当降雨在10～20 mm之间时,污染负荷的削减率仍然可以超过60%.相对总氮(TN)和总磷(TP)而言,下渗系统对悬浮物(SS)和化学需氧量(COD_(Cr))的去除能力要更高、更稳定.研究表明,径流下渗系统作为雨水管理的工具,在径流削减和改善水质方面具有良好的性能.     

植物根系质外体溶液的提取方法研究:以多环芳烃为例

根系质外体溶液中多环芳烃(PAHs)的分析对于阐明植物根系PAHs吸收运移机制及阻控意义重大.然而,迄今鲜有便捷成熟的植物根系质外体溶液提取方法的报道.为此,本研究以小麦为材料,菲为PAHs的代表,探究了植物根系质外体溶液的真空渗透离心提取方法.结果表明,小麦根系质外体菲提取量随真空度、真空时间、离心速率、离心时间的增加而增大;小麦根系质外体六磷酸葡萄糖脱氢酶(G6PDH)活性随真空度、真空时间、离心速率、离心时间的增加而升高.依据质外体溶液受原生质污染程度小于1%且尽量提取完全的原则,真空渗透离心提取法的最佳真空度为70 k Pa,最佳真空时间为10 min,最佳离心速率为3 068 r·min-1,最佳离心时间为15 min.研究结果可为污染物的植物根系质外体运输研究提供有效、简便的方法支撑.     

A critical review of the water quality classification system in Turkey: A case study on Meric Basin

An 11-year period of water quality data, collected by the Directorate of Sate Water Works of Turkey are thoroughly analyzed for the purpose of implementing water quality classes to water resources in the Meric Basin, located on the European land mass of Turkey. Water quality parameters are divided into four groups as physical, organic, inorganic, and bacteriological. The quality class of each group is evaluated by taking into account the poorest quality of any parameter in the group, after which a quality rank is assigned to the sampling station and the waterbody in question. This method of water quality classification imposed by the Turkish Water Quality Act, is then criticized with respect to a statistical approach.     

EVALUATION OF AN INDUCED INFILTRATION MODEL AS APPLIED TO GLACIAL AQUIFER SYSTEMS1

ABSTRACT: Numerical models were used to examine the limitations of the assumptions used in an analytical induced infiltration model. The assumptions tested included negligible streambed effects, negligible areal recharge, two-dimensional ground water flow, fully penetrating rivers and wells, and constant surface water stage. For situations that deviate from the underlying assumptions, the analytical model becomes a less reliable predictor of induced infiltration. The numerical experiments show that streambed effects cannot be neglected if the streambed conductivity is more than one order of magnitude lower than the aquifer hydraulic conductivity. Areal recharge cannot be neglected if the ground water basin receives more than 5 in/yr of areal recharge. Three-dimensional flow effects due to well partial penetration cannot be neglected if the ratio of horizontal hydraulic conductivity to vertical hydraulic conductivity (K_h/K_u) is greater than 10. Surface water elevation fluctuations can significantly influence the induced infiltration rate, depending on the degree of fluctuations and the ground water hydraulic gradient.