BOUNDARY AND SCALE: A HYDROLOGIC OBSERVATORY IN THE MISSISSIPPI EMBAYMENT

As a community, our ability to understand the terrestrial water budget and mass and energy fluxes on a river basin scale is limited by the lack of study areas and concerted research efforts designed to address hydrologic science questions across scales and boundaries. Developing an observatory network that provides this crucial data is of the utmost importance and doing so in a manner that is inclusive of all hydrologic disciplines that provide data across scales and boundaries is a daunting task. Researchers, as members of the MS Embayment Hydrologic Observatory Design Team, present the conceptual model of a functional hydrologic observatory (HO) designed to specifically focus on science questions and fill gaps in data needed to tackle critical regional/national water science and policy issues in the U.S.

The MS Embayment HO includes the Wolf River Basin and a swath of the MS River extending approximately 10 km on either side of a 200 km reach. The boundary of MS River reach that is to be included in this HO is founded on the existence of US Army Corps of Engineers’ gaging stations at Osceola, Memphis and Helena and a USGS regional aquifer investigation indicating lateral influence of the MS River being as far inland as 10 km.

The Wolf River is an atypical watershed, evolving from a pristine wetland habitat at the headwaters, to a highly urbanized environment in Memphis, TN. The sole source of drinking water for Memphis and the surrounding communities comes from one of the most prolific fresh water aquifer systems in the nation. Serving over one million citizens, Memphis is one of the larger if not the largest municipality in the nation solely dependent on ground water, pumping an average of 210 mgd, compared to the nearly 10 bgd of ground water drawn for irrigation the neighboring states of Arkansas and Mississippi, who compete for the same ground water sources. Pressing issues within this basin that require research efforts in multiple disciplines across varying scales include, among others, (a) contamination of and recharge reduction to the aquifer due to urban sprawl, (b) impact of aggradation/denudation of the Wolf River floodplain, (c) flooding and liquefaction potential, (d) ground-water/surface water interactions, and (d) maintaining habitats for rare and endangered species.