RAPID: Sediment, water, and nutrient flux and fate in Lake Pontchartrain from the 2011 Bonnet Carre Spillway Opening.

samuel Bentley, Sibel Bargu, Chunyan Li, Nan Walker, John R. white路易斯安那州立大学摘要密西西比河下游三角洲（MRD）居住着200万人口，是海上运输、渔业和能源方面的重要国家资源。MRD湿地和水域正在以惊人的速度退化，自20世纪30年代以来，已经失去了相当于特拉华州面积的湿地。下个世纪还会有更多。沿海水域的健康和湿地的命运在很大程度上受淡水流动及其附带的沉积物和营养物的支配，而这些现在主要由沿河的工程结构控制。由于这些原因，MRD的保护和恢复是下个世纪我国面临的突出的环境和社会经济挑战之一。了解和管理进入MRD海岸带的水、沉积物和营养物质的流动和命运是这一挑战的核心。2011年春季，密西西比河的水位已经超过了路易斯安那州许多地区1927年大洪水时的水位。为了缓解河堤的压力，水正通过邦纳卡罗莱泄洪道（BCS）排入庞恰特雷恩湖（LP），这是MRD内一个大部分封闭的大河口（图1）。BCS于5月9日开通，目前正在向LP输送创纪录的水量（8800立方米，相当于设计容量的116%），可能还有创纪录的沉积物和营养物质通量。了解这种羽流在LP中的动态和影响是很重要的，原因如下：(1)湖泊的营养负荷将产生潜在的有毒藻华；(2)淡水通量将导致较淡水湖与较咸的沿海海洋的强烈交换；(3)泥沙供给与沉积的测量与研究，将为三角洲工程引沙修复中泥沙的利用提供重要信息。随着时间的推移，pi将对水、沉积物、营养物质和浮游生物进行采样，以了解对湖泊的影响，以便更好地了解未来人为转移对三角洲恢复的影响。由于LP与其他MRD河口具有很强的相似性，并且工程引水和引沙是MRD保护和修复的主要工具，因此本工作的结果将直接适用于需要保护和修复的MRD大面积区域。

RAPID: Sediment, water, and nutrient flux and fate in Lake Pontchartrain from the 2011 Bonnet Carre Spillway OpeningEAR-1139997Samuel Bentley, Sibel Bargu, Chunyan Li, Nan Walker, John R. WhiteLouisiana State UniversityABSTRACTThe lower Mississippi River Delta (MRD), inhabited by 2 million people, is a critical national resource in terms of maritime transport, fisheries, and energy. MRD wetlands and waters are degrading at alarming rates, losing wetlands equivalent to the area of Delaware since the 1930?s, and more over the next century. The health of coastal waters and the fate of wetlands are strongly governed by the flow of fresh water and accompanying sediments and nutrients, which are now largely controlled by engineered structures along the river. For these reasons, conservation and restoration of the MRD is one of the outstanding environmental and socioeconomic challenges faced by our country over the next century. Understanding and managing water, sediment, and nutrient flux and fate into the MRD coastal zone is central to this challenge. The Spring 2011 hydrograph of the Mississippi River is reaching levels exceeding the Great Flood of 1927 in many locations in Louisiana. To provide relief to river levees, water is being released through the Bonnet Carré Spillway (BCS) into Lake Ponchartrain (LP), a large mostly enclosed estuary within the MRD (Fig. 1). BCS opening on May 9 is now producing record fluxes of water (8800 m3 s-1, 126% of design capacity) into LP, likely along with record fluxes of sediment and nutrients. Understanding the dynamics and impact of this plume in LP is important for several reasons: (1) nutrient loading to the lake will produce potentially toxic algal blooms; (2) fresh water flux will cause strong exchange of the fresher lake with the saltier coastal ocean; and (3), measurement and study of sediment supply and deposition will provide important information for use of sediment in engineered diversions for delta restoration. PIs will sample water, sediment, nutrients, and plankton over time to understand impacts to the lake, in order to better understand impacts from future manmade diversions for delta restoration. Because LP has strong similarities to other MRD estuaries, and engineered diversions of river water and sediment are primary tools planned for MRD conservation and restoration, results of this work will be directly applicable to large regions of the MRD in need of conservation and restoration.