NUTRIENT AND DISSOLVED OXYGEN TMDL FOR CHRISTINA RIVER BASIN

A total of 39 stream segments in the Christina River basin in Delaware and Pennsylvania are on the states' 303(d) lists of water-quality impaired waterbodies for nutrients and dissolved oxygen. Since the Christina River Basin spans multiple states, several agencies were involved in the project including EPA Region III (EPA), Delaware Department of Natural Resources and Environmental Control (DNREC), Pennsylvania Department of Environmental Protection (DEP), Maryland Department of the Environment (MDE), the Delaware River Basin Commission (DRBC), the University of Delaware Water Resources Agency, and the United States Geological Survey (USGS). At the request of DNREC and DEP, DRBC agreed to coordinate water management issues for the project. A cooperative and coordinated monitoring and modeling approach was undertaken by the agencies to develop and establish the Total Maximum Daily Loads (TMDLs). A calibrated hydrodynamic and water quality model was developed for nutrients and dissolved oxygen of the primary tidal and nontidal waterways in the Christina River watershed. The model was then applied for the development of TMDL allocations for carbon, nitrogen, and phosphorus loading from point and nonpoint sources. The model afforded a successful predictive tool for determining the nutrient load reductions necessary to meet water quality criteria in the impacted stream reaches. The TMDL allocation results and evaluation of the water quality management scenarios were presented to stakeholders through a series of public meetings as well as through distribution on the EPA Region III web site.