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

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

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.