Customization of BASINS for the North Sandy Pond Watershed, Oswego County, New York

North Sandy Pond is a small embayment of Lake Ontario in upstate New York. In 1996 it was listed on the Priority Waterbodies List for the Oswego-Seneca-Oneida River Basin as having “impaired boating and fishing with poor documentation.” This waterbody contains an overabundance of aquatic vegetation due to excessive nutrient loadings. The nutrient loadings are attributed to both non-point sources from the land surface and effluent from on-site septic systems in nearby communities. The goal of the project was to evaluate the relative impact of these nutrient inputs to North Sandy Pond in order to guide future management decisions. To achieve this goal, a combined watershed/water quality model was developed for the Oswego County Department of Planning. The modeling attempted to address four main issues: 1) What are the sources of nutrients to the pond? 2) What are the data gaps in the study area? 3) How does the pond respond to certain nutrient loadings? and 4) What is the impact of certain management practices on the water quality of the pond?Because the desire was to provide a user-friendly model for planning use, USEPA's BASINS 2.01 was customized for the County. BASINS existing watershed model, Non-Point Source Model (NPSM) was coupled to a customized water quality model that was written in FORTRAN and compiled as a stand-alone application to simulate the response of the pond to the watershed loadings and on-site septic system inputs. The final modeling tool operated entirely within the BASINS framework, providing a familiar interface for the user. This paper will overview the project and present the process involved with integrating an independent model into the BASINS tool. In addition, model development will be presented, with an overview of NPSM input data, constants, and parameters and a description of the mathematical process representation and input parameter specifications for the pond water quality model. Further, modeling results will be presented to highlight the use of this tool for evaluating the relative importance of nutrient inputs from the various subwatersheds and nearby septic systems to pond water quality.