草海湿地小流域土地利用与景观格局对氮、磷输出的影响

识别主要污染物和污染源对草海湿地生态系统的保护与管理具有重要的现实意义.基于2012年5—10月6个小流域的水质观测数据、土地利用结构与景观格局指数,研究了草海湿地入湖小流域氮、磷输出的时空变化规律及其与景观格局的关系,以期为草海湿地综合治理提供参考.结果表明,草海湿地北面建设用地面积比例呈西北、东南方向逐渐降低和景观破碎度逐渐减小的趋势,具有明显的城市-城郊-农村的景观格局梯度,景观格局影响流域水质.多元统计分析表明,小流域氮磷输出受景观组成属性和空间属性综合影响,城镇建设用地百分比与TN、TP和COD呈显著正相关关系(r分别为0.995、0.978和0.996,p0.01),景观破碎度(CONTAG、ED、MPS)和多样性(SHDI)与水质(TN、TP、COD)具有显著的相关关系,CCA的第一排序轴解释了建设用地面积比例、景观指数与水质指标相关性的96.0%.可见,威宁城镇化快速发展威胁了草海湿地生态安全,需进行草海周边城镇化进程的调整和控制.     

亚热带典型小流域总氮最大日负荷(TMDL)及影响因子研究——以金井河流域为例

本研究以亚热带红壤丘陵区为研究区域,选取10个典型小流域,根据土地利用和畜禽养殖密度分为4种类型(森林、森林-种植、养殖和种植-养殖小流域),并基于近3年小流域把口站的原位观测数据,采用负荷历时曲线模型(LDC)计算了不同类型小流域水体总氮(TN)的最大日负荷(TMDL),运用灰度分析法定量研究了不同流量阶段小流域主要因子对TN负荷消减率的影响.结果表明,小流域TN负荷特征与流域类型密切相关,10个小流域TN年均负荷为739.0~2798.4 kg·km-2·a-1,由小到大依次为森林、森林-种植、养殖、种植-养殖小流域,其中,养殖、种植-养殖小流域水质整体超标严重,且应针对中、低流量条件下(秋、冬季节)负荷进行消减,而森林-种植小流域TN负荷超标情况略好,但高流量阶段(春、夏)超标率过高.灰度分析结果表明,TN负荷消减率在高、中流量阶段下主要受农田面积比例影响,而低流量阶段受畜禽密度影响.农田面积比例对高、中流量段TN消减率影响显著,而畜禽养殖密度在低流量段具有更大影响,小流域景观越破碎、类型越丰富、斑块分布越零散、形状越复杂,TN负荷通量则越大.     

基于FLO-2D模型的红椿沟泥石流工程治理效果研究

汶川地震带来了众多地质灾害,给当地灾民造成了严重的生命和财产损失。为了更好地预防地质灾害的发生,保护灾后重建成果,对地质灾害防护工程的效果分析研究就显得尤为重要。文章选取了汶川红椿沟流域中的甘溪铺沟、大水沟、新店子沟3条泥石流沟为研究对象,采用二维流变模型FLO-2D,经连续方程与运动方程,结合网络化的数字高程模型,通过DEM在ArcGIS中转换为ASCII格式输入至FLO-2D软件中,建立流域模型,分析计算出红椿沟泥石流沟在工程治理条件下,遭遇50、100年一遇暴雨时,泥石流冲出物的堆积深度和流动速度。通过计算机数值模拟方法对治理效果进行分析研究,从而确定工程治理效果和进一步的工作方法。     

Management Implications of Snowpack Sensitivity to Temperature and Atmospheric Moisture Changes in Yosemite National Park,CA

In order to investigate snowpack sensitivity to temperature increases and end‐member atmospheric moisture conditions, we applied a well‐constrained energy‐ and mass‐balance snow model across the full elevation range of seasonal snowpack using forcing data from recent wet and dry years. Humidity scenarios examined were constant relative humidity (high) and constant vapor pressure between storms (low). With minimum calibration, model results captured the observed magnitude and timing of snowmelt. April 1 snow water equivalent (SWE) losses of 38%, 73%, and 90% with temperature increases of 2, 4, and 6°C in a dry year centered on areas of greatest SWE accumulation. Each 2°C increment of warming also resulted in seasonal snowline moving upslope by 300 m. The zone of maximum melt was compressed upward 100–500 m with 6°C warming, with the range reflecting differences in basin hypsometry. Melt contribution by elevations below 2,000 m disappeared with 4°C warming. The constant‐relative‐humidity scenario resulted in 0–100 mm less snowpack in late spring vs. the constant‐vapor‐pressure scenario in a wet year, a difference driven by increased thermal radiation (+1.2 W/m²) and turbulent energy fluxes (+1.2 W/m²) to the snowpack for the constant‐relative‐humidity case. Loss of snowpack storage and potential increases in forest evapotranspiration due to warming will result in a substantial shift in forest water balance and present major challenges to land management in this mountainous region.     

Addressing Declining Appropriations for Bureau of Reclamation Infrastructure: Policies Needed for Enabling Private Finance

Western water infrastructure was funded in the early and mid‐20th Century through federal financing through the Bureau of Reclamation. Over the past 30 years, federal financing has been less forthcoming, which has been commensurate with an increase in the need for financing rehabilitation and replacement of western irrigation infrastructure. As federal appropriations have declined, there has been increased interest in alternative approaches to infrastructure including public–private partnerships (P3s), loan guarantees, or title transfer of federal infrastructure. However, two of these approaches — P3s and loan guarantees — are precluded by existing federal budgetary policies, particularly Office of Management and Budget (OMB) scoring practices. If the OMB changed its policies for P3s or loan guarantees, private capital could play an important role in recapitalizing aging Reclamation infrastructure.     

Mitigating Groundwater Impacts of Residential Wells through Small‐Scale Distributed Storage in the Skagit River Basin

The exemption for groundwater wells for residential uses from the prior appropriations system, common in the western United States, has eroded in Washington State since about 2000 due to a series of legal cases. Water markets can allow the transfer of an existing water right, typically from an agricultural use, to compensate for the effect of a new residential well. But water must be legally and physically available in a way suitable to satisfy mitigation requirements. A recent court case in the Skagit basin in Northwestern Washington State has effectively halted residential development in rural areas of the basin because no suitable water rights are available to purchase for mitigation. This paper presents and examines the cost‐effectiveness of various water supply mitigation strategies. We find a small‐scale, distributed stream‐side storage system for augmenting instream flow purchased from downstream sources is relatively cost‐effective to mitigate against the effects of domestic groundwater use compared to more common alternatives. We consider transporting water to storage sites by both small‐gauge pipe and by truck. Overall, trucking water to stream‐side storage and release points tends to be more cost‐effective to mitigate against indoor‐use only given current subbasin housing densities, whereas piping for direct streamflow augmentation is more cost‐effective for higher mitigation needs associated with indoor and outdoor use and higher housing densities.     

漓江流域红壤侵蚀区植被演替与复合农林试验

漓江季节性的干旱和洪涝并存成为地方政府、有关专家和旅游行业密切关注的环境问题,漓江流域的环境建设尤其是上游森林植被恢复,成为生态治理重点内容。漓江上游红壤区植被类型主要包括针叶林、阔叶林、竹林、灌丛和草丛,植被的水分特征差异较大,植被的生态调节、水源涵养功能各异。在漓江上游红壤区开展4种模式的植被恢复和复合农林试验示范,3年的试验表明,乡土常绿阔叶树适应性强、有效保持水土,果林经济效益显著、但生态功能较差,木本药材林具有较好的生态功能和潜在的经济效益。通过调查和试验示范,提出亚热带红壤退化山地农林经营的植物种类和复合模式,对漓江流域水资源调控和水土流失治理提出建议和对策。     

浙西山区水库小流域放逸短沟蜷的空间格局

放逸短沟蜷(Semisulcospira libertina)是浙西山区水库小流域底栖螺类的优势种，定量采集不同环境条件的9个样点的标本，分别采用Taylor幂法则、Iwao聚集格局回归分析法及Morisita指数公式计算和统计分析，结果显示，所调查流域的放逸短沟蜷种群密度差异极显著，其种群空间格局理论上属于聚集型负二项分布，主要是由环境污染和流域底质所致。图2表3参10     

A study on the Spatial Distribution of Nitrogen and Phosphorus Balance, and Regional Nitrogen Flow Through Crop Production

The spatial distribution patterns of the nitrogen and phosphorus input/intake amounts in crop production within two small basins are examined, based upon a cropping unit distribution map that is obtained from remote sensing data analysis. Firstly, we examine the availability and suitability of approaches to the spatial distribution analysis of cultivation patterns classified from material flow characteristics of crop production using seasonal remote-sensing data. Secondly, material flow units in crop production are grouped according to the cultivation patterns obtained from the remote-sensing data analysis. Consequently, the spatial patterns of the amounts of both nitrogen and phosphorus inputs/intakes through crop production on farmland are examined and their spatial distribution maps are prepared according to the material flow units. In addition, we developed a nitrogen flow and runoff model and the model is simulated based on the examination of the results of spatial distribution patterns of the material flow units. The annual nitrogen runoff from small catchments, where various crops are cultivated, varies from 2.7 kg ha^–1 year^–1 to 108 kg ha^–1 year^–1 and the annual balanced losses of nitrogen in small catchments varied from –30 kg ha^–1 year^–1 to 101 kg ha^–1 year^–1. Also, the monthly changes in soil nitrogen of each material flow unit is estimated at –55 kg ha^–1 as a maximum decrease and 114 kg ha^–1 as a maximum increase. These results indicate that the spatial distribution patterns of nutrient input and intake through agricultural activities should be considered when analyzing the material flows and nutritient movement in soil–water systems in rural areas for watershed environmental control and regional agricultural management.     

小流域水土保持综合治理效益指标体系及其应用

在分析总结已有水土保持综合治理效益评价指标与方法的基础上,结合黄土高原沟壑区自然、经济、社会条件及治理特点,遴选了9个评价指标,并采用层次分析的方法对两个典型小流域的效益进行了评价。