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首页> 外文期刊>International Journal of Ecology & Enviromental Sciences >A Mississippi Flood Control Reservoir: Life Expectancy and Contamination
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A Mississippi Flood Control Reservoir: Life Expectancy and Contamination

机译：密西西比河防洪水库：预期寿命和污染

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The fate of reservoirs is a major water management, water quality, and aquatic life use concern across the globe. We examined sedimentation rates, current watershed contamination contributions and potential impacts of long-term row cropping (cotton, corn, soybeans, and sweet potato) in a large flood control reservoir in the loess hills of Mississippi, USA. Grenada Reservoir, created in January 1954, was constructed as part of a comprehensive plan for flood control in the Yazoo River Basin in northwestern Mississippi. Two rivers, the Yalobusha and Skuna, contribute inflow to the reservoir, forming a distinctive Y-shape within the topography of the flood pool. Total watershed drainage area for the reservoir is approximately 3,419 square kilometers (1,320 square miles). Reservoir sediment accumulation rates were sampled in 1998 and 1999. Although reservoir life expectancy was originally estimated at 25 years because of high erosion rates in the watershed, our study revealed that the reservoir continues to function with only slightly reduced storage capacity. Sediment accumulation within the permanent pool adjacent to the dam was < 1cm yr~(-1) except for a depositional area near tributary inflow that accumulated sediment at about 5 cm yr~(-1). The central area of the permanent pool experienced sediment accumulation rates that averaged < 1.5 cm yr~(-1). Sites within the two reservoir arms fed by the two river inflows showed little or no sedimentation. Sedimentation rates further upstream in these two inflow areas were also generally low. Sedimentation rates within Grenada Reservoir were higher until the mid 1960s & early 70s but were considerably lower thereafter. These lower sedimentation rates paralleled land use changes and followed discontinuance of major upstream channel alterations for flood control. From 1996 to 2002 analyses were conducted in water and sediment for 8 metals and 48 pesticides/ contaminants at 26 stream/river locations and 9 locations within the reservoir. In spite of long-term historical use of residual pesticides in the watershed and widespread use of currently applied agricultural compounds, concentrations in stream or reservoir sediments and overlying water were generally low and sporadic or not detectable. Conversely, several metals (arsenic, lead, copper, iron, aluminum and zinc) were abundant in stream and reservoir sediments. Atrazine, a triazine herbicide, was routinely found in stream water and sediment. It was also detected in reservoir water samples but at nearly one fifth less than contributing stream concentrations. Naturally occurring aluminum and iron were found in high concentrations. Residual pesticides were generally not detected in water but were detected in stream and reservoir sediments.
机译：水库的命运是全球主要的水管理，水质和水生生物利用问题。我们研究了美国密西西比州黄土丘陵的大型防洪库中的沉积速率，当前流域污染贡献以及长期行间种植（棉花，玉米，大豆和甘薯）的潜在影响。格林纳达水库建于1954年1月，是密西西比州西北部Yazoo流域防洪综合计划的一部分。 Yalobusha和Skuna这两条河流为水库注入了水，在洪水池的地形内形成了独特的Y形。该水库的总流域排水面积约为3,419平方公里（1,320平方英里）。 1998年和1999年对水库沉积物的蓄积率进行了采样。尽管最初估计水库寿命是25年，因为流域的侵蚀率很高，但我们的研究表明，水库继续发挥作用，但蓄水能力略有下降。除支流附近的沉积区在约5 cm yr〜（-1）处沉积有沉积物外，与大坝相邻的永久性池内的沉积物沉积物<1cm yr〜（-1）。永久性水库中心区域的沉积物沉积速率平均<1.5 cm yr〜（-1）。由两条河流流入的两个水库支臂内的站点很少或根本没有沉积。在这两个入流区域更上游的泥沙淤积率通常也很低。格林纳达水库内的泥沙淤积速率一直较高，直到1960年代中期和70年代初，但此后却大大降低。这些较低的沉积率与土地利用变化并存，随后主要的上游河道改造中断以防洪。从1996年到2002年，在水和沉积物中对26种溪流/河流位置和水库内9个位置的8种金属和48种农药/污染物进行了分析。尽管在流域中长期使用残留农药，并广泛使用了目前使用的农用化合物，但河流或水库沉积物和上覆水中的浓度通常较低，并且是零星的或无法检测到的。相反，河流和储层沉积物中富含几种金属（砷，铅，铜，铁，铝和锌）。通常在溪流水和沉积物中发现三嗪类除草剂阿特拉津。在水库水样中也检测到了它，但比贡献的溪流浓度低了近五分之一。天然存在的铝和铁含量很高。残留农药通常在水中未检出，但在河流和水库沉积物中检出。

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