Reducing Streamflow Forecast Uncertainty: Application and Qualitative Assessment of the Upper Klamath River Basin,Oregon1

Abstract: The accuracy of streamflow forecasts depends on the uncertainty associated with future weather and the accuracy of the hydrologic model that is used to produce the forecasts. We present a method for streamflow forecasting where hydrologic model parameters are selected based on the climate state. Parameter sets for a hydrologic model are conditioned on an atmospheric pressure index defined using mean November through February (NDJF) 700‐hectoPascal geopotential heights over northwestern North America [Pressure Index from Geopotential heights (PIG)]. The hydrologic model is applied in the Sprague River basin (SRB), a snowmelt‐dominated basin located in the Upper Klamath basin in Oregon. In the SRB, the majority of streamflow occurs during March through May (MAM). Water years (WYs) 1980‐2004 were divided into three groups based on their respective PIG values (high, medium, and low PIG). Low (high) PIG years tend to have higher (lower) than average MAM streamflow. Four parameter sets were calibrated for the SRB, each using a different set of WYs. The initial set used WYs 1995‐2004 and the remaining three used WYs defined as high‐, medium‐, and low‐PIG years. Two sets of March, April, and May streamflow volume forecasts were made using Ensemble Streamflow Prediction (ESP). The first set of ESP simulations used the initial parameter set. Because the PIG is defined using NDJF pressure heights, forecasts starting in March can be made using the PIG parameter set that corresponds with the year being forecasted. The second set of ESP simulations used the parameter set associated with the given PIG year. Comparison of the ESP sets indicates that more accuracy and less variability in volume forecasts may be possible when the ESP is conditioned using the PIG. This is especially true during the high‐PIG years (low‐flow years).     

Performance Assessment of Rain Gardens1

Abstract: The most widely used approach for evaluating the performance of stormwater best management practices (BMPs) such as rain gardens is monitoring, but this approach can involve a long time period to observe a sufficient number and variety of storm events, a high level of effort, and unavoidable uncertainty. In this paper, we describe the development and evaluation of three approaches for performance assessment of rain gardens: visual inspection, infiltration rate testing, and synthetic drawdown testing. Twelve rain gardens in Minnesota underwent visual inspection, with four determined to be nonfunctional based on one or more of the following criteria: (1) presence of ponded water, (2) presence of hydric soils, (3) presence of emergent (wetland) vegetation, and (4) failing vegetation. It is believed that these rain gardens failed due to a lack of maintenance. For the remaining eight rain gardens, an infiltrometer was used to determine the saturated hydraulic conductivity (K_sat) of the soil surface at several locations throughout each basin in what is termed infiltration rate testing. The median K_sat values for the rain gardens ranged from 3 to 72 cm/h. Synthetic drawdown testing was performed on three rain gardens by filling the basins with water to capacity where possible and recording water level over time. The observed drain times for two of those rain gardens were in good agreement with predictions based on the median of the infiltrometer measurements. The observed drain time for the third rain garden was much greater than predicted due to the presence of a restrictive soil layer beneath the topsoil. The assessment approaches developed in this research should prove useful for determining whether the construction of the rain garden was performed properly, a rain garden is functioning properly, and for developing maintenance tasks and schedules.     

生物填料地下渗滤系统处理生活污水的中试研究

以活性污泥等生物基质为填料.在不同的水力负荷和有机负荷条件下,研究了地下渗滤系统对生活污水的处理效果.中试结果表明:地下渗滤系统对COD、NH_4~+-N和TP有着良好的去除效果,在水力负荷为4 cm·d~(-1),污染负荷为280 mg·L~(-1)和320 mg·L~(-1)时.COD、NH_4~+-N和TP的去除去分别达到91.2%、97.2%、88.0%和90.6%、95.6%、90.4%;水力负荷达到450 mg·L~(-1)时,有机物及氨氮的去除率下降迅速,仅为83.2%和85.5%,TP的去除率略有提高,为91.7%;平均污染负荷为300 mg·L~(-1),水力负荷为4.0 cm·d~(-1)、6.5 cm·d~(-1)和8.1 cm·d~(-1)时,COD、NH+4_4~+-N和TP的去除率分别达到90.6%、97.4%、90.0%.87.3%、96.8%、84.0%和85.6%,96.3%,83.3%;适宜的生活污水处理条件是水力负荷为8.1 cm·d~(-1),污染负荷低于450 mg·L~(-1).在以上工况下的出水水质均优于生活杂用水水质标准(CJ251-89)和沈阳市污水处理中水回用标准,处理效果稳定;系统垂直方向的氨化细菌分布较均匀,硝化细菌在70 cm以上区域数量较多,反硝化细菌在70 cm以下区域数量较多;氨化细菌与COD、NH_4~+-N和TN的去除率的相关性显著,硝化及反硝化细菌与COD、NH_4~+-N和TN的去除率的相关性极显著;氨化、硝化和反硝化细菌与TP的去除率的相关性均不显著,说明生物作用不是TP脱除的主要途径.     

乌江流域梯级水库入出库河流中总汞和甲基汞的时空分布

2006年1~12月,每月采集乌江流域梯级水库入出库河流水样,用两次金汞齐-冷原子荧光光谱法和蒸馏-乙基化结合GC CVAFS法测定了水中总汞和甲基汞的浓度。结果表明：（1）入出库河流中总汞年均加权浓度分别为317和 2.34 ng/L,甲基汞为014和 0.18 ng/L。（2）不同水库入出库河流中总汞和甲基汞的时空分布特征不同,位于上游第一级的普定和洪家渡水库入库河流中总汞有明显的季节变化趋势,且显著低于出库河流;而甲基汞的季节变化在出库河流中较为明显,而且库龄大的普定、东风、乌江渡水库出库河流中甲基汞浓度显著高于入库河流。（3）相关分析发现水库入库河流中总汞、甲基汞浓度主要受悬浮颗粒物的影响,而与水量间的相关性因水库所处位置的不同而有差异,上游的普定和洪家渡水库中呈显著正相关,其它水库中呈负相关。     

三级人工快渗系统脱氮效果及菌种分布分析

为了更有效地去除污水中的氮类污染物,采用三级串联人工快渗系统对高氨氮生活污水进行脱氮性研究,同时进行系统内菌种分布的特征分析,从微观角度对比传统人工快渗和新式三级串联人工快渗系统中微生物分布的区别。结果表明三级串联人工快渗系统对氨氮和总氮(TN)的去除率较常规人工快渗系统分别提高5%和21%。三级串联人工快渗系统内硝化细菌和反硝化细菌总数均大于传统人工快渗系统。反硝化细菌数量的显著提高是总氮(TN)去除提高的主要原因。同时发现三级串联人工快渗系统可以有效地缓解堵塞现象的发生。     

潜在泥石流的界定与判识——以金沙江流域溪洛渡库区为例

选择在建的溪洛渡库区作为研究区域,通过详细的野外考察,确定金沙江流域溪洛渡库区干流共有现代活动泥石流沟57条。利用Matlab构建SOM神经网络模型,依据这57条泥石流样本,选择流域面积、主沟长度、相对高差、沟床比降、平均坡度、相对切割程度、圆状率和侵蚀程度等8个指标,对干流46条沟谷进行预测。预测结果分为：①非泥石流沟有19条,分布在雷波-永善三角台地上;②低危险潜在泥石流沟有14条,分布在库区尾端;③高危险潜在泥石流沟有13条,分布于库区中间位置。预测结果可以为库区生态修复和工程治理提供依据。     

近50年湘江流域干湿气候变化若干特点

采用M-K突变、小波分析、空间变异系数、经验正交函数分解法（EOF）和旋转经验正交函数分解法（REOF）等方法,对近48年来湘江流域40个测站干湿指数（Z指数）进行了分析。研究表明：湘江流域1960年代前期和1980年代为干旱期,1990年代为湿润期。1980年代末有向湿润转变趋势,2003年后又开始向干旱转变。湘江流域干湿的年际变化较小,降水相对稳定,存在3年、6年和10年和21年4个特征时间尺度,且未来几年湘江流域将仍处于干旱期。湘江流域干湿变化具有很好的主体一致性,依据空间异常类型可分为南部、中部、北部和西南部4个区域。     

基于博弈论的南四湖流域生态补偿理论分析

采用博弈论的分析方法寻找南四湖流域生态补偿主客体的纳什均衡。在静态博弈模型和动态博弈模型得出两个截然不同的均衡：静态博弈的均衡是（不保护,不补偿）,动态博弈的均衡是（保护,补偿）。在静态博弈中进行激励设计,提高补偿客体保护水资源的积极性,实现帕累托最优,应该立法,制定严格的惩罚标准;动态分析是建立在完全信息的基础上,由此要求政府建立良好的信誉,才能保证均衡的长久,从而达到保护南四湖流域生态环境的目的。     

Projections of 21st Century Sierra Nevada Local Hydrologic Flow Components Using an Ensemble of General Circulation Models1

Abstract: Sierra Nevada snowmelt and runoff is a key source of water for many of California’s 38 million residents and nearly the entire population of western Nevada. The purpose of this study was to assess the impacts of expected 21st Century climatic changes in the Sierra Nevada at the subwatershed scale, for all hydrologic flow components, and for a suite of 16 General Circulation Models (GCMs) with two emission scenarios. The Soil and Water Assessment Tool (SWAT) was calibrated and validated at 35 unimpaired streamflow sites. Results show that temperatures are projected to increase throughout the Sierra Nevada, whereas precipitation projections vary between GCMs. These climatic changes drive a decrease in average annual streamflow and an advance of snowmelt and runoff by several weeks. The largest streamflow reductions were found in the mid‐range elevations due to less snow accumulation, whereas the higher elevation watersheds were more resilient due to colder temperatures. Simulation results showed that decreases in snowmelt affects not only streamflow, but evapotranspiration, surface, and subsurface flows, such that less water is available in spring and summer, thus potentially affecting aquatic and terrestrial ecosystems. Declining spring and summer flows did not equally affect all subwatersheds in the region, and the subwatershed perspective allowed for identification for the most sensitive basins throughout the Sierra Nevada.     

长江流域水电站施工区生活垃圾特性及处理处置决策模型研究

随着中国长江流域水电开发进入高峰期,大量的建设人员进入水电站施工营地,导致施工区的生活垃圾处理处置问题日益凸显。通过对金沙江HPS1水电站、雅砻江HPS2水电站和HPS3水电站、大渡河HPS4水电站施工区生活垃圾状况的调查表明,水电站施工生活区生活垃圾人均产量平均值约为0.68kg/d;以厨余、渣土、纸类塑料和橡胶为主,电池等危险废物含量甚微;容重、低位热值、生物可降解物质量分数的平均值分别为358kg/m3、5 234kJ/kg、43.22%。结合施工区所处的环境条件和周围的市政设施现状,采用层次分析法和最小成本法,构建了长江流域水电站施工区生活垃圾处理处置决策模型,可为大型水电站开发过程中施工区生活垃圾全过程管理提供指导。根据决策模型计算得出,HPS1、HPS2、HPS4水电站施工区生活垃圾最优处理处置技术为卫生填埋,HPS3水电站以外运综合处理最优。