The Aging of America's Reservoirs: In‐Reservoir and Downstream Physical Changes and Habitat Implications

Reservoirs are important for various purposes including flood control, water supply, power generation, and recreation. The aging of America's reservoirs and progressive loss of water storage capacity resulting from ongoing sedimentation, coupled with increasing societal needs, will cause the social, economic, environmental, and political importance of reservoirs to continually increase. The short‐ and medium‐term (<50 years) environmental consequences of reservoir construction and operation are well known and include an altered flow regime, lost connectivity (longitudinal, floodplain), an altered sediment regime, substrate compositional change, and downstream channel degradation. In general, reservoir‐related changes have had adverse consequences for the natural ecosystem. Longer term (>50 years) environmental changes as reservoirs enter “old” age are less understood. Additional research is needed to help guide the future management of aging reservoir systems and support the difficult decisions that will have to be made. Important research directions include assessment of climate change effects on aging and determination of ecosystem response to ongoing aging and various management actions that may be taken with the intent of minimizing or reversing the physical effects of aging.     

云南昌宁玉地里温泉水文地球化学特征及形成模式

以水化学及同位素技术为基础,对昌宁县玉地里温泉的地质及地热特征进行了研究,并取得了一些重要的认识.通过对比研究该温泉地下热水1980年和2012年的水文地球化学数据,发现经过30多年的循环演化,其水化学类型仍为HCO3-Na型.δD和δ18O同位素为该温泉首次获得,数据显示地下热水具有现代大气降水的氢氧同位素组成特征,属断裂带对流型深循环低温地下热水系统,其补给源区位于东部和南部山区,热储层和盖层的构造及岩性特征与地下热水的深循环和化学组成有着密切联系.     

贵州东风水库沉积物间隙水中溶解态汞及甲基汞的分布特征及界面交换

为弄清水库沉积物间隙水中汞及甲基汞的分布及扩散特征,于2009年春、夏两季对东风水库进行了采样,分别采用两次金汞齐-CVAFS法和蒸馏-乙基化结合GC-CVAFS法测定沉积物间隙水中溶解态(DHg)和甲基汞(DMeHg)浓度。结果表明夏季沉积物间隙水DHg浓度远高于春季,而DMeHg浓度却略低于春季;沉积物间隙水中DHg和DMeHg均有向上覆水体扩散的趋势,其夏季扩散通量高于春季;间隙水中DMeHg对上覆水体的贡献率大于DHg,最高可达30%,再次证明了沉积物间隙水中的DMeHg是其上覆水体的重要来源。     

水库渗漏水流溶解氧与水温沿程恢复的试验研究

水库底层低温低氧水从坝体下泄或渗漏,可能对下游生态产生不利影响。通过对湖北温峡水库下游温峡河225 km河段的野外试验,测量溶解氧、水温等指标的日变化和沿程变化,开展复氧试验研究阶梯深潭结构和沙洲对溶解氧的影响,并取样分析大型底栖无脊椎动物的沿程分布。结果表明,流速对水温与溶解氧日变化规律无明显影响。试验河段水温和溶解氧恢复很快,经过17 km的河段,水温从123℃升高至300℃,且溶解氧饱和度基本达到饱和。河宽对水温恢复起重要作用,对溶解氧影响较小,对复氧速度基本无影响。流量通过改变淹没程度影响阶梯深潭的复氧能力。溶解氧在沙洲下游存在横向分布,滞水区溶解氧高于左右汊道。溶解氧是水库下游水生态的控制因素,物种多样性随溶解氧的升高而增加     

Effects of artificially induced complete mixing on dissolved organic matter in a stratified source water reservoir

Naturally complete mixing promotes the spontaneous redistribution of dissolved oxygen(DO), representing an ideal state for maintaining good water quality, and conducive to the biomineralization of organic matter. Water lifting aerators(WLAs) can extend the periods of complete mixing and increase the initial mixing temperature. To evaluate the influence of artificial-induced continuously mixing on dissolved organic matter(DOM) removal performance, the variations of DOM concentrations, optical cha...     

Evidence on the causes of the rising levels of CODMn along the middle route of the South-to-North Diversion Project in China: The role of algal dissolved organic matter

As the biggest inter-basin water transfer scheme in the world,the South-to-North Water Diversion Project（SNWD） was designed to alleviate the water crisis in North China.The main channel of the middle route of the SNWD is of great concern in terms of the drinking water quality.In this study,we tested the hypothesis that the dissolved organic matter（DOM） derived from the planktonic algae causes the rising levels of COD_Mn along the middle route by monitoring data on water quality（2015-20...     

滇中高原水库外源污染负荷贡献解析与环境容量核算

为探究高原型水库上游流域的污染负荷来源及其贡献率,并计算水库的水环境容量,以云南高原柴石滩水库为研究对象,应用排污系数法估算了水库上游流域污染来源,运用水文和水质同步监测资料计算入库污染负荷,采用富营养化模型核算了不同水质目标情景下水库TN和TP的最大容量.结果表明：(1)柴石滩水库及其以上流域主要特征污染物为TN和TP;(2)水库上游流域的COD和TP主要来源于农村面源污染,贡献率分别为49.40%和50.11%; NH⁺₄-N和TN主要来源于城镇生活污染,贡献率分别为45.76%和33.77%;农村面源污染贡献中,陆良县COD和TP贡献率最大,分别为34.82%和36.82%;城镇生活污染贡献中,麒麟区COD、 NH⁺₄-N、 TN和TP贡献率最大,均高达65%.(3)COD、 NH⁺₄-N、 TN和TP污染负荷入河量分别为28 050.90、2 465.16、4 680.54和870.93 t·a^-1,TN和TP污染负荷入库量分...     

长江中上游表层沉积物重金属形态分布特征及风险评价

大坝蓄水显著改变了河流的水文情势,进而影响着河流沉积物的颗粒组成和重金属形态.2019年6～7月,从长江上游金沙江攀枝花市至长江中游湖口县,沿长江干流调查了26个断面,采用欧共体BCR 3步提取法分析了沉积物中8种重金属(As、 Cd、 Co、 Cr、 Cu、 Ni、 Pb和Zn)的含量及其赋存形态,并用重金属地累积指数法、沉积物质量基准法和风险评价编码法(RAC)对沉积物重金属污染程度和生物有效性进行风险评价.结果表明,长江上游库区段(金沙江梯级水库段和三峡库区段)从上游至下游沉积物的粒径均值呈减小趋势,沉积物As和Zn全量呈增加趋势,中游段变化规律不明显.沉积物黏粒含量与弱酸提取态Cd和Ni含量呈显著正相关.Cd以残渣态(59.26%)和弱酸提取态(24.67%)为主,Cr(92.41%)和Ni(83.41%)以残渣态为主,As、 Co、 Cu、 Pb和Zn以残渣态和可还原态为主.As、 Cd、 Co、 Cr、 Ni和Zn污染程度大小为：金沙江段>长江中游段>三峡库区段.Cd、 Co、 Cr、 Cu、 Ni和Zn的生物有效性(RAC均值)大小：上游三峡段>中游段&...     

Daily Bank Erosion Rates in the Lower Yellow River Before and After Dam Construction

During the period of water impoundment and sediment detention of the Sanmenxia Reservoir, riverbank erosion processes played a key role in the channel evolution of the Lower Yellow River (LYR). However, research into bank erosion rates of the LYR has been neglected due to the lack of direct field monitoring. In this study, an indirect method is proposed to determine bank erosion rates at daily time scales by outlining a detailed calculation procedure using measured hydrological data. A total of 810 data points of daily bank erosion rates before and after the construction of Sanmenxia Dam was calculated at seven hydrometric sections along the LYR, with the corresponding values of the bank stability coefficient and the width‐to‐depth ratio also being calculated. Empirical relations were then developed to estimate the daily bank erosion rates, using these parameters at the sections. Temporal and spatial variability in daily bank erosion rates in the LYR before and after dam construction were also investigated, revealing that: (1) the bank erosion rates had a mean value of 16.7‐29.1 m/day in the braided reach, with a maximum value of 290.0 m/day, while they were relatively low in the meandering reach, with a mean value of 2.5 m/day; (2) the erosion rates before dam construction were slightly greater than those after dam construction, with the difference reaching 5‐10 m/day in the braided reach, decreasing in the transitional reach gradually, and being slight in the meandering reach.     

Upstream Sediment‐Control Dams: Five Decades of Experience in the Rapidly Eroding Dahan River Basin,Taiwan

Sedimentation is emerging as a key issue in sustainable reservoir management. One approach to controlling reservoir sedimentation is to trap sediment in hydraulic structures upstream of the reservoir. In the 1,163‐km² catchment of the Dahan River (Taiwan) over 120 “sabo” dams were built to reduce sediment yield to Shihmen Reservoir. Built in 1963 for water supply, Shihmen has lost over 40% of its 290‐Mm³ storage capacity to sedimentation. Most of these upstream structures were small, but three had capacities >9 Mm³. Field measurements and historical data from the Water Resources Agency show most smaller dams had filled with sediment by 1976. The three largest were full or nearly so by 2007, when one (Barlin Dam) failed, releasing a pulse of 7.5 Mm³, most of its 10.4 Mm³ stored sediment downstream. The Central Range of Taiwan is rapidly eroding (denudation rates 3‐6 mm/yr), so geologically high loads make sediment problems manifest sooner. Even in other environments, however, eventually small dams built upstream of large reservoirs are likely to fill themselves, creating multiple small sediment‐filled reservoirs, some located in sites inaccessible to mechanical removal. Our analysis suggests sabo dams do not offer a long‐term basis for controlling reservoir sedimentation in such a high‐sediment yield environment. Sustainable solutions must somehow pass sediment downstream, as would be accomplished by a sediment bypass around Shihmen Reservoir, as now being studied.