Streamflow Response to Climate as Influenced by Geology and Elevation1

Mayer, Timothy D. and Seth W. Naman, 2011. Streamflow Response to Climate as Influenced by Geology and Elevation. Journal of the American Water Resources Association (JAWRA) 47(4):724‐738. DOI: 10.1111/j.1752‐1688.2011.00537.x Abstract: This study examines the regional streamflow response in 25 predominately unregulated basins to warmer winter temperatures and snowpack reductions over the last half century in the Klamath Basin of California and Oregon. Geologic controls of streamflow in the region result in two general stream types: surface‐dominated and groundwater‐dominated basins. Surface‐dominated basins were further differentiated into rain basins and snowmelt basins on the basis of elevation and timing of winter runoff. Streamflow characteristics and response to climate vary with stream type, as discussed in the study. Warmer winter temperatures and snowpack reductions have caused significantly earlier runoff peaks in both snowmelt and groundwater basins in the region. In the groundwater basins, the streamflow response to changes in snowpack is smoothed and delayed and the effects are extended longer in the summer. Our results indicate that absolute decreases in July‐September base flows are significantly greater, by an order of magnitude, in groundwater basins compared to surface‐dominated basins. The declines are important because groundwater basins sustain Upper Klamath Lake inflows and mainstem river flows during the typically dry summers of the area. Upper Klamath Lake April‐September net inflows have decreased an estimated 16% or 84 thousand acre‐feet (103.6 Mm³) since 1961, with the summer months showing proportionately more decline. These changes will exacerbate water supply problems for agriculture and natural resources in the region.     

Nonstationarity: Flood Magnification and Recurrence Reduction Factors in the United States1

Vogel, Richard M., Chad Yaindl, and Meghan Walter, 2011. Nonstationarity: Flood Magnification and Recurrence Reduction Factors in the United States. Journal of the American Water Resources Association (JAWRA) 47(3):464‐474. DOI: 10.1111/j.1752‐1688.2011.00541.x Abstract: It may no longer be reasonable to model streamflow as a stationary process, yet nearly all existing water resource planning methods assume that historical streamflows will remain unchanged in the future. In the few instances when trends in extreme events have been considered, most recent work has focused on the influence of climate change, alone. This study takes a different approach by exploring trends in floods in watersheds which are subject to a very broad range of anthropogenic influences, not limited to climate change. A simple statistical model is developed which can both mimic observed flood trends as well as the frequency of floods in a nonstationary world. This model is used to explore a range of flood planning issues in a nonstationary world. A decadal flood magnification factor is defined as the ratio of the T‐year flood in a decade to the T‐year flood today. Using historical flood data across the United States we obtain flood magnification factors in excess of 2‐5 for many regions of the United States, particularly those regions with higher population densities. Similarly, we compute recurrence reduction factors which indicate that what is now considered the 100‐year flood, may become much more common in many watersheds. Nonstationarity in floods can result from a variety of anthropogenic processes including changes in land use, climate, and water use, with likely interactions among those processes making it very difficult to attribute trends to a particular cause.     

珠江三角洲两条主要河流沉积物中的典型内分泌干扰物污染状况

为了调查珠江三角洲河流沉积物中典型内分泌干扰物的污染状况,采用超声提取-衍生化-GC/MS法研究了双酚A(BPA)、雌酮(E1)、雌二醇(E2)、己烯雌酚(DES)、17α-乙炔雌二醇(EE2)、雌三醇(E3)等典型内分泌干扰物在珠江广州河段和东江东莞河段表层沉积物中的质量分数水平、分布特征,并对其来源进行了分析。结果显示,BPA在所有样品中均有检出,E1和E2的检出率分别为72%和61%,其质量分数(以干质量计)分别在14.3～429.5 ng.g-1之间(中值为79.5 ng.g-1)、<1.3～10.9ng.g-1之间(中值为3.4 ng.g-1)和<0.9～2.6 ng.g-1之间(中值为1.6 ng.g-1);其余几种雌激素均未被检出。东江东莞河段沉积物中BPA的污染水平整体高于珠江广州河段,而天然雌激素的污染状况则是珠江广州河段更为严重。3种化合物的质量分数总体呈现出沿河口方向降低的分布特征,这可能与沿岸工业废水和生活污水不规则排放以及水动力条件有关。BPA、E1、E2的质量分数均与沉积物总有机碳(TOC)质量分数呈正相关,表明有机质是控制沉积物中内分泌干扰物分布的一个重要因素。     

Development and modelling of realistic retrofitted Nature-based Solution scenarios to reduce flood occurrence at the catchment scale

Decentralized Nature-based Solutions such as Urban Green Infrastructures (UGI) are increasingly promoted to reduce flooding in urban areas. Many studies have shown the effectiveness of flood control of UGI at a plot or neighbourhood level. Modelling approaches that extrapolate their flood reducing impact to larger catchment scales are often based on a simplistic assumption of different percentages of UGI implementation. Additionally, such approaches typically do not consider the suitable space for UGI and potential implementation constraints. This study proposes a scenario development and modelling approach for a more realistic upscaling of UGI based on empirical insights from a representative neighbourhood. The results from this study, conducted in the metropolitan area of Costa Rica, show that upscaling the full potential for UGI could significantly reduce surface runoff, peak flows, and flood volumes. In particular, the permeable pavement has the highest potential for flood reducing in public space while cisterns perform best at the property level. These results can guide the formation of policies that promote UGI.Supplementary InformationThe online version of this article (10.1007/s13280-020-01493-8) contains supplementary material, which is available to authorized users.     

中哈跨境河水质标准及评价方法对比研究

中哈跨境河流的水量与水质,是双方共同关注的重要问题。对比了中哈跨境河水质标准及评价方法的差异性。中国采用的是单因子水质评价方法,哈萨克斯坦采用的是综合评价方法。中国与哈萨克斯坦跨境河水质监测指标数不同,但相同指标的标准限值在同一数量级。讨论了综合评价法与单因子评价法优势与不足。指出中哈跨境河水质标准与评价方法的统一,是双方合作研究急需解决的问题。建议综合两个标准体系,组成双方共同的地表水标准限值指标体系。建议对两国执行的评价方法,采各家之长优势互补,对环境及人体健康有严重影响的毒理性指标,必须执行单因素评价方法,在此基础上,对其他指标进行综合评价。     

人工补水条件下的缺水河流生态修复综合评价方法

构建了人工补水条件下的缺水河流生态修复多目标综合评价指标体系,对生态修复中影响评价指标量化结果的因素进行了综合考虑,提出了包含主、客观因子并反映层次关系的综合权重确定方法,进而建立了一种人工补水条件下的缺水河流生态修复综合评价方法,以更好地解决多目标决策中的总目标量化问题.最后,以正在建设的永定河生态修复工程为例,通过构建典型的生态修复情景方案,对建立的评价指标体系进行应用,确定各评价指标的综合权重系数,并对构建的情景决策方案进行了综合评估,验证本文提出的评价指标权重综合调整的必要性,说明构建的人工补水条件下的缺水河流生态修复综合评价方法的合理性与可行性.结果表明,所提出的评价方法不仅对人工补水条件下的河流生态修复决策具有一定的实用价值,而且对其它类型生态修复多目标综合决策评价也具有借鉴意义.     

城市污染河道沉积物有机质的氧化稳定性

为了研究城市河道沉积物有机质的氧化稳定性,以氧化稳定系数(Kos)和腐殖化程度(HA/FA)作为评价指标,在用H2O2处理沉积物的基础上,探讨城市污染河道有机质含量、有机质组成等对氧化稳定性的影响.结果显示,污染河道沉积物有机质含量明显高于自然水生态系统沉积物有机质含量;富里酸(FA)、胡敏酸(HA)、胡敏素(HM)是污染河道沉积物有机质主要赋存形式,其中胡敏素是主体,占全部有机质的65%以上;易氧化有机质(OMr)和难氧化有机质(OMd)与总有机质含量均显著正相关(P0.05);OMd的含量可以更直观地反映河道污染程度;重污染河道沉积物有机质去除量较高;随着有机质的去除,沉积物Kos在总体上有上升的趋势;不同形态有机组分其Kos差异性明显(P0.05),以HM为主的紧结态腐殖质的Kos值最高;用HA/FA和OMr可从大体上表征沉积物的氧化稳定性;HA、FA是影响城市河道沉积物氧化稳定性的主要因素.     

Rapid Geomorphic and Habitat Stream Assessment Techniques Inform Restoration Differently Based on Levels of Stream Disturbance

Visual‐based rapid assessment techniques provide an efficient method for characterizing the restoration potential of streams, with many focusing on channel stability and instream habitat features. Few studies, however, have compared these techniques to see if they result in differing restoration priorities. Three rapid assessment techniques were contrasted at three wild trout streams in western New York with different amounts of channel disturbance. Two methods focused only on geomorphic stability, whereas the third addressed physical habitat condition. Habitat assessment scores were not correlated with scores for either geomorphic assessment method and they varied more between channels with different degrees of disturbance. A model based on dynamic equilibrium concepts best explains the variation among the streams and techniques because it accounts for a stream's capacity to maintain ecological integrity despite some inherent instability. Geomorphic indices can serve as effective proxies for biological indices in highly disturbed systems. Yet, this may not be the case in less disturbed systems, where geomorphic indices cannot differentiate channel adjustments that impact biota from those that do not. Dynamically stable streams can include both stable and unstable reaches locally as characterized by geomorphic methods and translating these results into restoration priorities may not be appropriate if interpretations are limited to the reach scale.     

Oregon Hydrologic Landscapes: A Classification Framework1

Wigington, Parker J., Jr., Scott G. Leibowitz, Randy L. Comeleo, and Joseph L. Ebersole, 2012. Oregon Hydrologic Landscapes: A Classification Framework. Journal of the American Water Resources Association (JAWRA) 1‐20. DOI: 10.1111/jawr.12009 Abstract: There is a growing need for hydrologic classification systems that can provide a basis for broad‐scale assessments of the hydrologic functions of landscapes and watersheds and their responses to stressors such as climate change. We developed a hydrologic landscape (HL) classification approach that describes factors of climate‐watershed systems that control the hydrologic characteristics of watersheds. Our assessment units are incremental watersheds (i.e., headwater watersheds or areas draining directly into stream reaches). Major components of the classification include indices of annual climate, climate seasonality, aquifer permeability, terrain, and soil permeability. To evaluate the usefulness of our approach, we identified 30 rivers with long‐term streamflow‐gauging records and without major diversions and impoundments. We used statistical clustering to group the streams based on the shapes of their annual hydrographs. Comparison of the streamflow clusters and HL distributions within river basin clusters shows that the Oregon HL approach has the ability to provide insights about the expected hydrologic behavior of HLs and larger river basins. The Oregon HL approach has potential to be a useful framework for comparing hydrologic attributes of streams and rivers in the Pacific Northwest.     

Estimation of the nutrient inputs into river systems – experiences from German rivers

The nutrient discharges from point and diffuse sources in more than 200 German river basins were estimated for the periods 1983–1987 and 1993–1997 employing the MONERIS model. This model distinguishes between six diffuse pathways and point source emissions from waste water treatment plants and direct industrial discharges. It was estimated that the total nitrogen input into the German river systems amounts to about 819,000 t N year^–1 in the period 1993 to 1997. These emissions have decreased since the mid-eighties by about 266,000 t N year^–1, mainly caused by the reduction of point discharges. For phosphorus the emissions have been reduced by 56,290 t P year^–1 and amount to 37,250 t P year^–1 in the period 1993–1997. Based on emission data a retention module estimates riverine nutrient loads. The comparison of the model output with the observed loads shows a deviation as low as 30% and 50% for nitrogen and phosphorus, respectively. The regional resolution of the model indicates the relative importance of different pathways for phosphorus and nitrogen input into river systems. Electronic Publication