Collaborative Research: Evaluating Groundwater Discharge into River-Dominated Coastal Waters; A Multiple Tracer Approach Grant uri icon

abstract

  • The transport of groundwater into coastal zones may be a significant process in the geochemical, nutrient, and carbon budgets of many marine nearshore waters. This project will address the manner in which we may evaluate interactions between groundwater and surface water on river-dominated margins. Recent studies have suggested that groundwater may play an important role in transporting water and bioactive elements to coastal waters along both typical continental shelves and river dominated ocean margins. Relationships between groundwater, the substrate through which it flows, and the receiving surface waters are of significant environmental concern since the magnitude of SGD in not yet assessed along most of the world's coastlines. The problem is how to quantitatively assess the extent of groundwater flow. The major goal of this study is to develop a comprehensive approach that would allow an unequivocal estimate of groundwater discharge and the associated dissolved constituents to river-dominated shelf waters. This project will develop and apply a novel multiple-tracer approach to this problem. We will employ 222Rn and 3He/tritium as natural tracers of groundwater flow on the margin adjacent to the Mississippi River. In order to evaluate the connection between groundwater inputs and surface water tracer inventories, we will construct a balance of all possible inputs and outputs of these natural tracers. Our approach is to assess all flux terms and to estimate the groundwater contribution by difference. In addition to the geochemical work to be performed in the coastal waters, wells located near the Louisiana coast and the lower Mississippi will be measured quarterly for tracer concentrations, nutrients, metals, and water level (relative to mean sea level). This data will be used to develop a hydrologic model for the study area. Model results will be compared to estimates of groundwater flow obtained from geochemical modeling. We suggest that one of the most effective ways to address the question of quantifying subsurface flow into standing bodies of water is by integrating geochemical and hydrogeological techniques. This would offer the scientific community an extremely important tool for environmental assessment, not only for the coastal zone, but lakes and other standing bodies of water as well.

date/time interval

  • October 2002 - June 2006