桂江流域岩溶碳汇特征

为研究岩溶区碳汇动态变化特征,使用德国Merck公司生产的碱度计每月定期对桂江流域14个岩溶大泉和16条地下河出口水中HCO3-含量进行了现场测定。结果表明桂江流域枯水期(11月至次年2月)地下水中HCO3-含量平均为223.62mg/L,平水期(3月、9月)为222.11mg/L,丰水期(4月至8月)为210.19mg/L,枯水期和平水期的HCO3-平均含量比丰水期高13.43mg/L和11.92mg/L。尽管丰水期的HCO3-平均含量不及枯水期和平水期,但其平均流量最大,是平水期的2倍,枯水期的2.8倍,因此其岩溶碳汇量也最大,是平水期的4.7倍,是枯水期的2.7倍。在碳汇构成上,丰水期的岩溶碳汇量占年总碳汇量的63.13%,而平水期和枯水期只分别占年总碳汇量的13.35%和23.51%。      

Implementing Integrated Catchment Management in the upper Limpopo River basin: A situational assessment

A three-phase study was initiated as a way to promote Integrated Catchment Management approaches in the Limpopo River basin. This paper presents the situational assessment, which should enable De Beers to understand how their Venetia Mine operations are located within a broader and highly dynamic socio-economic and ecohydrological landscape as it pertains to water risks. The second phase, Risk assessment, aims to develop conservation interventions in the identified areas; the third phase will develop mechanisms for implementing water stewardship schemes to mitigate the shared water risks.Analysis of the social-ecological system (hydrological, climatic, ecological, socio-economic and governance systems) of the Limpopo River basin indicates that the institutional arrangement of the Limpopo River basin is neither simple nor effective. The basin is rapidly approaching closure in the sense that almost all of the available supplies of water have already been allocated to existing water users. If the proposed ecological flow requirements were to be met for all of the tributaries, the basin would be ‘closed’. On-going and projected land use changes and water resources developments in the upper reaches of the basin, coupled with projected rainfall reductions and temperature increases, and allocation of the flows for the ecological reserve, are likely to further reduce downstream river flows. The coupled increase in temperature and decrease in rainfall is of great concern for everyone in the basin, especially the poorer communities, who rely on rain-fed agriculture for their livelihoods. Increased temperatures also lead to increased evaporation from reservoirs and therefore result in a decrease in water availability. This will lead to increased abstraction of groundwater, especially from alluvial aquifers, and consequently an increase in river transmission losses and a decrease in river flows.     

Data assimilation for distributed hydrological catchment modeling via ensemble Kalman filter

Catchment scale hydrological models are critical decision support tools for water resources management and environment remediation. However, the reliability of hydrological models is inevitably affected by limited measurements and imperfect models. Data assimilation techniques combine complementary information from measurements and models to enhance the model reliability and reduce predictive uncertainties. As a sequential data assimilation technique, the ensemble Kalman filter (EnKF) has been extensively studied in the earth sciences for assimilating in-situ measurements and remote sensing data. Although the EnKF has been demonstrated in land surface data assimilations, there are no systematic studies to investigate its performance in distributed modeling with high dimensional states and parameters. In this paper, we present an assessment on the EnKF with state augmentation for combined state-parameter estimation on the basis of a physical-based hydrological model, Soil and Water Assessment Tool (SWAT). Through synthetic simulation experiments, the capability of the EnKF is demonstrated by assimilating the runoff and other measurements, and its sensitivities are analyzed with respect to the error specification, the initial realization and the ensemble size. It is found that the EnKF provides an efficient approach for obtaining a set of acceptable model parameters and satisfactory runoff, soil water content and evapotranspiration estimations. The EnKF performance could be improved after augmenting with other complementary data, such as soil water content and evapotranspiration from remote sensing retrieval. Sensitivity studies demonstrate the importance of consistent error specification and the potential with small ensemble size in the data assimilation system.     

降雨输入对实时洪水预报精度与预见期的影响

针对降雨输入不确定性对实时洪水预报影响的问题,本文采用不考虑未来预报降雨、考虑未来预报降雨、考虑预报降雨的降雨量误差和降雨时间误差4种方法,以陕西省两个半湿润流域（陈河流域和大河坝流域）为研究区域,分析不同预见期和不同降雨输入情况下洪水预报的精度.研究表明：相对于不考虑未来降雨情况,考虑未来降雨后在预报预见期较长时对预报结果精度提升较大,在预见期较短时对预报结果精度提升不显著;暴雨中心位置不同对预报精度影响也不同,当暴雨中心位于流域下游时降雨量误差对流量预报误差影响更大;降雨量误差主要影响洪量相对误差和洪峰相对误差,且这种影响是线性的,对确定性系数的影响是非线性的二次函数,降雨时间误差主要影响峰现时间误差.     

淮河流域周村水库夏季CDOM吸收光谱特征、空间分布及其来源分析

基于2015年8月采集的24个淮河流域以周村水源水库为代表的表层水样的有色溶解性有机物(CDOM)吸收系数数据,研究了CDOM吸收光谱的空间分布特征,考察了CDOM的吸收系数与水质参数的相关关系,同时探讨了周村水库夏季CDOM的潜在来源.结果显示:依据CDOM的吸收光谱空间分布特性及采样点分布特征,周村水库分为入库口、过渡区和主库区3个特征水域;CDOM的吸收系数沿入库口到主库区依次递减,S值呈现相反的趋势;分析发现S240~500与a(355)和a*(355)呈极显著负相关(R~2=0.98、0.88);CDOM吸收系数a(355)与溶解性有机碳(DOC)浓度具有良好的线性相关,有利于建立DOC遥感反演模型;同时,CDOM吸收系数a(355)与a_(ph)(440)存在极显著正线性相关,表明浮游植物的新陈代谢及其降解产物是夏季周村水库CDOM的潜在来源.综上,通过对夏季周村水库水体CDOM的研究,丰富了关于水源水体CDOM的调查资料,可为日后水库的管理提供技术支撑.     

淮河流域瓦埠湖流域水体污染研究与现状评价(2011-2015年)

瓦埠湖位于淮河中游南岸,属于淮河流域最大的湖泊.根据2011年8月-2015年12月对瓦埠湖湖区3个监测点位、入（出）湖河流4个监测断面的水质监测数据,选用内梅罗水污染指数法和单因子指数法,以总氮、总磷、铵态氮和高锰酸盐指数为评价指标对瓦埠湖湖区水体和主要入（出）湖河流水质现状进行评价,结果表明：瓦埠湖湖区总体水质状况为轻度污染、Ⅳ类水质,其主要污染源为农业面源污染和生活污染;部分入湖河流受农业氮、磷污染的影响水质较差,其中庄墓河污染情况最为严重.因此,必须加强流域的水环境综合整治工作,控制农业面源污染对流域水环境的影响.     

巢湖流域塘西河上游分流制系统降雨径流污染特征及初期冲刷效应

研究城市径流水质变化及初期冲刷效应对控制与治理城市径流污染具有重要指导意义.对塘西河上游6次降雨径流水质水量进行监测分析,计算次降雨径流平均浓度(EMC)和单位面积次降雨径流污染负荷(EPL),作M(V)曲线图研究初期冲刷现象.结果表明:降雨径流中悬浮物(SS)、化学需氧量(CODCr)和总磷(TP)的EMC值相对较大;SS的EMC值波动最为显著;总氮(TN)、TP、COD_(Cr)、SS间的EMC值均呈正相关;TN的EMC值与降雨量呈负相关性.各污染物EPL值与各降雨特征间均呈正相关性,经估算2015年研究区在6-8月共有10.38 tTN、2.29 tTP、1022.43 t SS、161.70 t CODCr和5.18 t NH_3-N随降雨径流排入巢湖;降雨量和雨前干期是城市径流污染的主要影响因素;以FF5050为初期冲刷效应判别依据,5种污染物均有初期冲刷效应出现,冲刷程度表现为SSCODCrTPTNNH_3-N;各水质指标的初期冲刷强度与降雨特征之间无相关性;雨型对初期冲刷现象影响较大;当降雨强度达1.36 mm/h即有径流汇集流出时开始截流,截流时间取440 min,截取的最大径流量取224319.14 m~3.     

甘肃省各流域降水量的GIS模块插值估计与改进

考虑了我国西部流域降水量的主要因素,应用GIS插值模块及其改进方法以甘肃省为例对不同流域单元区年平均降水量进行插值估计,并进行了分析对比.改进方法是:根据气象台站海拔高度面与数字高程模型DEM(Digital Elevation Model)之间的海拔高度差,并以流域地形坡面、不同流域单元降水的垂直变化率为参数,引入ArcGis的 Spline、IDW、Kriging 3个模块进行插值.结果表明:与气象站降水量统计值相比,这不仅更有效地表达降水量空间分布变异程度,而且通过调整参数和反复验证可有效地提高插值精度,以弥补西部流域气象台站稀少所造成的数据空白,避免某些方法或模型(如PRISM)对上述流域降水模拟估计值偏小的不足.     

Evaluation of River Water Quality Simulations at a Daily Time Step – Experience with SWAT in the Axe Catchment,UK

The Water Framework Directive (WFD) was established for the protection of surface waters (rivers, lakes, transitional and coastal waters) and ground waters in the European Union. The main environmental objective is to achieve and maintain a good status for all waters by the target date of 2015. Models which are able to address the majority of environmental objectives are proposed within the WFD to inform the management changes required to meet current water policy goals. The use of the Soil and Water Assessment Tool (SWAT) catchment model is widespread throughout the world, especially to support river basin management as required by the WFD. This paper provides a critical evaluation of the use of the model by placing model performance in the Axe catchment, UK, in the context of international performance of the model. Within the constraints of the available data, SWAT represents hydrology, sediment and ortho‐phosphorus concentration well for this heterogeneous catchment, but the representation of daily nitrogen concentration dynamics is poor. Temporal aggregation of model outputs from daily to monthly improved the performance metrics for all the river outputs, including nitrate. Wider review of SWAT studies showed widespread reporting of monthly performance metrics within the SWAT studies, despite the model operating at a daily time step. Poor performance for nitrate identified in this current study may be a significant factor in the choice to not report daily results. This demonstrates the importance of ascertaining the reasons for the use of temporal aggregation in modelling studies.