HYDROLOGIC RESPONSES OF AN AGRICULTURAL WATERSHED TO VARIOUS HYDROLOGIC AND MANAGEMENT CONDITIONS1

ABSTRACT: The hydrologic responses from an agricultural watershed in southeast Nebraska were investigated under an array of physiographic, hydrologic, meteorologic, and management conditions. For analytical purposes, the hydrologic responses were narrowed to include only runoff and sediment yield. The study was performed by utilizing the ANSWERS (Areal Nonpoint Source Watershed Environment Response Simulation) hydrologic-simulation model. Results of this study indicate that, generally, nonstructural (agronomic) Best Management Practices (BMPs) have a more significant impact in controlling erosion and nonpoint-source pollution than structurally oriented BMPs. The percentage of reduction in average soil loss as a result of changing tilage systems from conventional to chisel plow was in the mid-40s. The corresponding percentages of reduction in sediment yield from the watershed under minimum tillage and no-till systems were in the mid-60s and mid-80s, respectively. The impact of these management strategies on runoff varied considerably. That is primarily based on the watershed's antecedent soil moisture condition, land use, and the growth stage of crops. Generally, an intense, short, thunderstorm type of rainfall event had more relative impact on runoff, and therefore sediment yield than a long, gentle, and steady event.     

Phosphorus export by runoff from agricultural field plots with different crop cover in Lake Taihu watershed

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平原井灌区土壤水库调蓄能力分析

20世纪80年代以来,由于干旱少雨,北方井灌地区农田地下水位普遍下降,由此使得农田土壤的蓄水能力发生变化。论文根据北京市水利科学研究所在北京市东南郊水资源试验区取得的试验资料,以0～3m土层作为土壤水库的界定深度,分析其对降雨的调蓄能力;经计算,1991～1995年间,春末夏初雨季前,土壤水库的有效调节能力,多年平均值为137.4mm(0～2m)和188.8mm(0～3m)。分析表明,0～3m层土壤有很好的蓄雨调节能力,雨季平均有近85%的降水量滞蓄在3m土层内,其余蒸腾、蒸发散失或补给地下水。研究认为,在田间采取一定的拦蓄水措施,即使遇到10年一遇24小时p=200mm这样的大暴雨,是可以做到农田地表不产流或少产流,从而最大限度地拦蓄汛期降水,增加土壤水资源量的。     

卡尔曼滤波理论在预报地面径流污染中的应用

本文主要介绍流域径流污染的系统分析方法，并提出采用卡尔曼滤波理论进行仿真，从而实现污染的预报。     

榆林地区能源基地建设水资源保证程度及供水措施

榆林地区是我国重要的能源基地，水资源贫乏是影响该地区工业发展的重要因素。本文通过对区内水资源及其开发利用条件、供需平衡分析后认为，只要兴建水库，调节径流及加强污水处理，增加区域供水能力，区内水资源可以基本满足近阶段经济发展的用水需求。     

城市降雨径流污染及最佳治理方案探讨

城市降雨径流污染已经成为非点源污染的一个新亮点,随着城市工业废水和生活污水等点源治理力度的加大,城市降雨径流污染问题将越来越突出.文章系统阐述了城市降雨径流污染的过程、污染类型及来源、污染物特征,对各种具体的城市降雨径流污染控制与治理技术进行了总结,并着重介绍了城市降雨径流污染最佳管理措施,还提出了实施城市降雨径流污染治理的具体对策和指导思想.     

农业流域“汇”型景观结构对径流调控及磷污染物截留作用的研究

选取天津于桥水库北岸桃花寺流域作为实验流域,进行了流域景观格局对生态水文及磷污染物迁移转化过程影响的野外实验研究.研究结果表明,流域中广泛分布于季节性河流附近的汇型景观结构(石坝、植草水道、植被过滤带、干塘、缓冲区等),通过滞留/缓冲功能,对地表径流的流速及流量具有双重调控作用,延长了养分物质在流域内部的滞留时间,对产生于不同源区的面源污染径流具有截留、吸纳、贮存作用,使径流中泥沙和磷素浓度逐渐得到降低,减少了养分对下游水体的负荷输出.多次降雨径流的监测结果表明,无论在大暴雨下的连续流事件还是在小雨下的间断流事件中,汇型景观结构均能表现出良好的养分持留功能.在2003年6月22日连续径流事件中,地表径流的流速可由系统入口处的37.2 cm·s-1降至系统出口处的11.1 cm·s-1,污染径流体积可削减50.2%,TSS、TP、TDP、DRP的持留率分别可达72.7%,69.3%,59.8%和57.9%.在间断径流事件中,污染径流全部为汇型景观结构所截留,泥沙和磷素的持留率更高.对21场降雨-径流事件的统计分析结果表明,干塘和植被过滤带是本实验流域控制污染物输出较为稳定的两种结构.     

Influence of body condition and weather on departures of first-year European robins, <Emphasis Type="Italic">Erithacus rubecula</Emphasis>, from an autumn migratory stopover site

How migratory birds decide when to leave a stopover site is important to the understanding of bird migration strategies. Our study looks at how body condition and the weather affect the decision to depart on nocturnal migratory flight. During two autumn migration seasons (2002–2003), we radio tracked 51 first-year European robins, Erithacus rubecula, at a stopover site on the Courish Spit (Eastern Baltic) from the first day after landing until their migratory departure. The tagged robins stopped over for 1–14 days. There was no clear relationship between stopover duration and energetic condition on arrival. Weather conditions (wind, precipitation, and cloud cover) on departure differed measurably between years. In 2002, robins took off mainly under following winds and clear skies. In 2003, there were mainly light head winds and partially cloudy or overcast skies. This could be explained by the year-specific role of weather factors in making the decision to depart. In both years, robins making short (1–2 days) stopovers took off in more varied weather situations than those individuals with long stopovers. This suggests that robins from the former group were more inclined to continue with migration than longer-stay birds that, apart from re-fuelling, could be waiting for favourable weather. The lack of a relationship between stopover duration and body condition and some departures under unfavourable weather conditions suggest that endogenous spatiotemporal programmes may play an important role in controlling stopover duration in robins.     

Bioavailability of zinc in runoff water from roofing materials

Corrosion and runoff from zinc-coated materials and outdoor structures is an important source for the dispersion of zinc in the environment. Being part of a large inter-disciplinary research project, this study presents the bioavailability of zinc in runoff water immediately after release from the surface of 15 different commercially available zinc-based materials exposed to the urban environment of Stockholm, Sweden. Runoff water was analysed chemically and evaluated for its possible environmental impact, using both a biosensor test with the bacteria Alcaligenes eutrophus (Biomet^®) and the conventional 72 h growth inhibition test with the green alga Raphidocelis subcapitata. Chemical speciation modelling revealed that most zinc (94.3–99.9%) was present as the free Zn ion, the most bioavailable speciation form. These findings were confirmed by the results of the biosensor test (Biomet^®) which indicated that all zinc was indeed bioavailable. Analysis of the ecotoxicity data also suggested that the observed toxic effects were due to the presence of Zn²⁺ ions. Finally, regression analysis showed that, for this type of runoff samples, the rapid screening biosensor was capable of predicting (a) the total amount of zinc present in the runoff samples (R² of 0.93–0.98; p<0.05) and (b) the observed 72 h-EbC₅₀s (R² of 0.69–0.97; p<0.05).     

高速公路降雨径流污染特征及其污染控制

随着高速公路的快速发展,路面降雨径流污染引起了越来越多的关注.从高速公路路面雨水径流中污染物成分及其影响因素、径流污染迁移模型和径流污染物对受纳水体水质的影响等方面,对路面降雨径流污染特征进行了综述,并从工程和非工程措施两方面比较了目前高速公路路面降雨径流污染治理措施的特点和适用条件,最后提出了进一步研究的建议,希望为有关方面的研究提供借鉴.