近四十年来长江源区河流水沙量的变化

长江源区是指直门达水文站以上长江干支流的广大集水区域，是长江的重要水源涵养区。通过统计分析直门达站1957－1999年的43a间年径流量和年输沙量的变化情况，得出几个基本结论：长江源区年径流的变化主要受气候等自然因素的影响，年径流周期性变化较为明显，径流丰水年，偏丰水年出现最多的年份是20世纪60年代和80年代，枯水年和偏枯年出现最多的年份是70和90年代，总体上看40年间节径流基本稳定，但90年代比80年代有趋向偏枯的现象；年输沙量与年径流量的变化基本同步，年输沙量的变化主要取决于年径流量的变化，年输沙量也呈弱周期性变化状态，并有趋向减少的势头，近10a直门达站年径流量呈递减的趋势导致了年输沙量呈相应的变化；长江源区径流量和输沙量年内主要集中在5－10月，分别占年径流量和年输沙量的87．3％和99％；沱沱河由于径流以冰川补给为主，径流量与输沙量的变化呈现出不同的特征。     

Study on Management and Control of Nonpoint Source Pollution from Urban Surface Runoff

Urbanization is the dominant form of land-use change in terms of impacts on water quality, hydrology, physical properties of watersheds and their nonpoint source （NPS） pollution po-tential at present. Urbanization has changed the source, process and sink of urban NPS pollution, especially raised the pollution load of urban runoff NPS in receiving water. Urban runoff pollution is a hot spot of research on NPS. This paper analyzed type, source and harm of the NPS pollutants of urban runoff and its influence on the receiving water. Through estimating NPS pollution load of urban runoff and summarizing the law and characteristics of urban runoff NPS systemically, study on management and control of urban runoff NPS pollution was focused on the application of BMPs （best management practices）. It is a fresh methodology that management and control on NPS pollution from urban surface runoff was analyzed by methods of landscape ecology, environmental economics and environmental management. The paper provided a scientific reference for mitigating urban water environment pressure and an effective method for management and control of NPS pollution from urban surface runoff.     

Impacts of Climate Variability and Land Use Alterations on Frequency Distributions of Terrestrial Runoff Loading to Coastal Waters in Southern California1

Abstract: The transport of water, sediment, dissolved and particulate chemicals, and bacteria from coastal watersheds affects the nearshore marine and estuarine waters. In southern California, coastal watersheds deliver water and associated constituents to the nearshore system in discrete pulses. To better understand the pulsed nature of these watersheds, frequency distributions of simulated runoff events are presented for: (1) three land use conditions (1929, 1998, 2050); (2) three time periods (all water years 1989‐2002), only El Nino years (1992, 1993, 1995, 1998); and only non‐El Nino years; and (3) three regions (watershed, uplands, and lowlands). At the watershed scale, there was a significant increase (>200%) in mean event runoff from 1929 to 2050 (0.4‐1.3 cm) due to localized urbanization, which shifted the dominant sources of runoff from the mountains in 1929 (78% of watershed runoff) to the coastal plane for 2050 conditions (51% of watershed runoff). Inter‐annual climate variability was strong in the rainfall and runoff frequency distributions, with mean event rainfall and runoff 66 and 60% larger in El Nino relative to non‐El Nino years. Combining urbanization and climate variability, 2050 land conditions resulted in El Nino years being five times more likely to produce large (>3.0 cm) runoff events relative to non‐El Nino years. Combining frequency distributions of event runoff with regional nutrient export relationships, we show that in El Nino years, one in five events produced runoff ≥2.5 cm and temporary nearshore nitrate and phosphate concentrations of 12 and 1.4 μM, respectively, or approximately 5‐10 times above ambient conditions.     

Measuring the Impact of Urbanization on Channel Widths Using Historic Aerial Photographs and Modern Surveys1

Abstract: Land use in a watershed is commonly held to exert a strong influence on trunk channel form and process. Land use changes act over human time‐scales, which are short enough to measure effects on channels directly using historic aerial photographs. We show that high‐resolution topographic surveys for the channels of paired watersheds in the Lehigh Valley, Pennsylvania, are comparable, but have channel widths that have changed dramatically in the past five decades. The two watersheds, Little Lehigh Creek and Sacony Creek, are similar in most aspects except in their respective amount of urban land use. Aerial photographs of the urbanized Little Lehigh Creek show that a majority of the measured widths (67 of 85) were statistically wider in 1999 than in 1947. In contrast, the measured widths from the agricultural Sacony Creek are more evenly distributed among those that widened (18), narrowed (28), and those that were statistically unchanged (6) from 1946 to 1999. From 1946 to 1999 the only section of Sacony Creek that widened was that reach downstream of the only sizable urban area in the watershed. The current land use in Sacony Creek watershed resembles that of 1946, while the Little Lehigh Creek watershed has more than tripled its urban area. These data, in concert with other recent hydrologic data from the watersheds suggest that the increase in urban area‐generated peak discharges is the mechanism behind the widening that occurred in the Little Lehigh Creek. These wider channels can affect water quality, aquatic habitat, suspended sediment loads, and river esthetics.     

Spatial Distribution of Water Supply in the Coterminous United States1

Abstract: Available water supply across the contiguous 48 states was estimated as precipitation minus evapotranspiration using data for the period 1953‐1994. Precipitation estimates were taken from the Parameter‐Elevation Regressions on Independent Slopes Model (PRISM). Evapotranspiration was estimated using two models, the Advection‐Aridity model and the Zhang model. The evapotranspiration models were calibrated using precipitation and runoff data for 655 hydrologically undisturbed basins, and then tested using estimates of natural runoff for the 18 water resource regions (WRR) of the 48 contiguous states. The final water supply coverage reflects a mixture of outputs from the two evapotranspiration models. Political, administrative, and land cover boundaries were mapped over the coverage of mean annual water supply. Across the entire study area, we find that 53% of the water supply originates on forested land, which covers only 29% of the surface area, and that 24% originates on federal lands, including 18% on national forests and grasslands alone. Forests and federal lands are even more important in the West (the 11 western contiguous states), where 65% of the water supply originates on forested land and 66% on federal lands, with national forests and grasslands contributing 51%.     

对城市雨水地下回灌的分析

城市扩张带来雨水径量增大,排出时间缩短并由此产生一系列后果,对城区雨水回灌地区的效益进行了讨论,分析城区雨水径流水质污污状况及其影响因素,初期雨水径流污染严重,主要受到地面条件,屋面材料,气温,降雨量及降雨强度等影响,根据对雨水水质的研究结果,分析了雨水回灌地下的条件及必要的雨水处理措施,对雨水回灌技术作了简略的论述。     

上海市城区非渗透性地面径流的污染特性研究

通过2003～2005年连续3 a对上海市城区非渗透性地表径流的采样与检测,获得了19个采样点56组径流水样污染物（COD、BOD₅、SS、NH⁺₄-N、TP、TN）浓度随降雨历时的变化过程线.据此分析了径流污染物浓度的变化规律及其与降雨特性之间的关系,计算了地表径流水质的事件平均浓度,分析了事件平均浓度的分布规律及其与降雨特性参数之间的相关关系.研究表明,上海市区非渗透性地面径流事件平均浓度中值（mg/L）为：COD 205,BOD₅ 68,SS 185,NH⁺₄-N 3.14,TP 0.40,TN 7.23,大大高于法国巴黎同类研究的结果;BOD₅与COD的比值约为0.37,明显高于发达国家相关监测的结果.结果表明,上海市城区地表径流污染严重,即使实现了理想的分流制也难以控制面源污染对城市水环境的危害.     

Comparison of Stormwater Lag Times for Low Impact and Traditional Residential Development1

Abstract: This study compared lag time characteristics of low impact residential development with traditional residential development. Also compared were runoff volume, peak discharge, hydrograph kurtosis, runoff coefficient, and runoff threshold. Low impact development (LID) had a significantly greater centroid lag‐to‐peak, centroid lag, lag‐to‐peak, and peak lag‐to‐peak times than traditional development. Traditional development had a significantly greater depth of discharge and runoff coefficient than LID. The peak discharge in runoff from the traditional development was 1,100% greater than from the LID. The runoff threshold of the LID (6.0 mm) was 100% greater than the traditional development (3.0 mm). The hydrograph shape for the LID watershed had a negative value of kurtosis indicating a leptokurtic distribution, while traditional development had a positive value of kurtosis indicating a platykurtic distribution. The lag times of the LID were significantly greater than the traditional watershed for small (<25.4 mm) but not large (≥25.4 mm) storms; short duration (<4 h) but not long duration (≥4 h) storms; and low antecedent moisture condition (AMC; <25.4 mm) storms but not high AMC (≥25.4 mm) storms. This study indicates that LID resulted in lowered peak discharge depth, runoff coefficient, and discharge volume and increased lag times and runoff threshold compared with traditional residential development.     

RUNOFF EVENT IMPACTS ON A WATER SUPPLY RESERVOIR: SUSPENDED SEDIMENT LOADING, TURBID PLUME BEHAVIOR, AND SEDIMENT DEPOSITION1

Abstract: The impacts of runoff events on external suspended solids loading to Schoharie Reservoir, New York, and patterns of light scattering and sediment deposition in this reservoir are assessed. The assessment is based on monitoring of suspended solids concentrations in the reservoir's primary tributary, detailed vertical profiles of optical backscattering (a surrogate measure of light scattering) in the reservoir water column, and analysis of sediment trap collections, over a seven-month interval of high runoff. These impacts are reported to be tightly temporally coupled and strongly positively related to the magnitude of runoff events. The primary tributary entered the reservoir as a plunging inflow during runoff events, causing conspicuous subsurface peaks in light scattering, with vertical patterns that varied strongly for different events. Deposition quantified by near-bottom trap deployments is reported to be more representative than results from metalimnetic deployments that were generally within, rather than below, the turbid layers. Direct inputs of sediment, transported by density currents, are found to drive deposition, rather than resuspension/redeposition. More than 50 percent of the reported deposition occurred in less than 15 percent of the study period, associated with the four largest runoff events.