Book Description

Development of total maximum daily loads (TMDLs) for critical pollutants in impaired watersheds is becoming a standard approach in environmental management. This requires the identification of future loading of contributing pollutants, and the development of a plan to allocate the necessary reductions among the point and nonpoint sources in the watershed to achieve this loading. To support water quality model-based TMDL development, US EPA has released the modeling framework BASINS-Better Assessment Science Integrating Point and Nonpoint Source, which incorporates several watershed water quality models within a GIS-based data management system. Current capabilities of BASINS enable simulation of watershed water quality associated with a TMDL, thus supporting TMDL development via a trial-and-error approach. The limitations of the trial-and-error approach are addressed via systematic search procedures implemented within the Water Quality Management Decision Support System (WQMDSS) that is designed to aid stakeholders and decision-makers efficiently identify TMDLs. The focus of the research presented in this paper is to demonstrate the applicability of WQMDSS in developing TMDLs for a realistic illustrative case study. Using the data for the Suwanee Creek Watershed in Georgia, which underwent a recent TMDL study, a series of illustrative scenarios are examined to consider varying target total suspended solids (TSS) loading rates, as well as different instream water quality parameters. The instream water quality is estimated using a calibrated HSPF model. Future land use development plans, with and without consideration of riparian buffer strips for nonpoint source control, to meet instream water quality goals are identified. Through this illustrative study, a range of uses of WQMDSS in watershed-scale TMDL development is demonstrated.