RAPID: COLLABORATIVE RESEARCH: The 2011 Historic High Flows in the Atchafalaya Basin: How will Hydrologic transport Alter Nutrient Retention (C and N)?

通过森林湿地——特别是密西西比河下游流域——转移富含营养的水是减少向沿海河口出口营养物质的一种建议方法。本研究的主要目的是量化河水通过阿恰法拉雅流域洪道系统（ABFS）时的营养保留和碳矿化。研究小组通过对经流域渠化部分输送的水进行表征，并与未渠化的溢洪道（包括森林沼泽）进行对比，希望发现由于停留时间增加和与洪泛区沉积物接触增加，通过溢洪道转移的水中营养物质的去除能力增强。将在洪水期间（12周）收集整个流域的样本。将测量水同位素和保守阴离子，以量化水源和推断水停留时间。营养物质（磷和氮种）将被测量，以量化系统处理和描绘整个ABFS的空间差异。虽然引水是减少墨西哥湾养分输出和相关缺氧区范围的一种建议方法，但大规模引水对养分减少幅度的影响尚不清楚。目前密西西比河下游的洪水（自1927年以来的最高水位）导致美国陆军工程兵团自1973年以来首次开放摩根萨溢洪道进入ABFS。通过ABFS探索营养丰富的密西西比河水的命运的机会是前所未有的，并将为阿恰法拉亚河和洪泛区的水文和生物地球化学耦合提供有价值的见解。该研究将对与大规模泉水径流分流相关的养分减少提供见解。

The diversion of nutrient-rich water through forested wetlands--especially within the Lower Mississippi River Basin--is one proposed approach to reduce nutrient export to coastal estuaries. The primary objective of this research is to quantify nutrient retention and carbon mineralization as river water is transported through the Atchafalaya Basin Floodway System (ABFS). By characterizing water transported via channelized sections of the basin in contrast to the un-channelized spillway including the forested swamps, the research team expects to find enhanced nutrient removal within water diverted through the spillway due to increased residence time and enhanced contact with floodplain sediments. Samples will be collected across the basin over the flood period (12 weeks). Water isotopes and conservative anions will be measured to quantify water sources and infer water residence time. Nutrients (phosphorus and nitrogen species) will be measured to quantify system processing and delineate spatial differences across the ABFS.Although diverting water is a proposed approach to reduce nutrient export, and associated hypoxic zone extent, in the Gulf of Mexico, the effect of very large-scale diversion on the magnitude of nutrient reduction is not well understood. The current flooding in the Lower Mississippi (highest levels since 1927) has resulted in the Army Corps of Engineers opening the Morganza Spillway into the ABFS for the first time since 1973. The opportunity to explore the fate of the nutrient-rich Mississippi water through the ABFS is unprecedented and will provide valuable insight into the coupling of hydrology and biogeochemistry of the Atchafalaya River and Floodplain. This study will provide insights on nutrient reduction associated with large scale diversion of spring runoff water.