GIS EVALUATION OF POTENTIAL IMPACTS TO WATER QUALITY, OAK ORCHARD CREEK WATERSHED, NEW YORK

The Oak Orchard Watershed is located in Western New York and discharges into Lake Ontario. It occupies most of Orleans County and parts of Genesee County. The waters in the Oak Orchard have many use values including recreational boating and sport fishing. The watershed comprises 173,975 acres including two urban areas, but land use within the watershed is primarily agriculture. Soils within the basin are highly fertile, supporting diverse agriculture including livestock, vegetable crops, cash crops and fruit farms. Several water quality concerns exist in this watershed including lack of an MS4 stormwater program, a total of thirteen combined sewer overflows, four CAFO and the potential for non-point source agricultural discharge. Currently, the Oak Orchard Creek is a USEPA 303d listed impaired stream.

Snap shot water sampling was conducted in the spring of 2005. Water samples were analyzed for major cations and anions and trace elements using ICP-AES and ion chromatography. Samples were found to have concentrations of total phosphorous, nitrate and in some locations sulfate above recommended levels, ranging up to 2.1mg/L, 9.1 mg/L and 1066 mg/L, respectively. This poses several potential health risks for the stream including clogging navigable waters with aquatic plants and algae, and the potential for decreases in dissolved oxygen.

GIS is being used to identify potential problems in the watershed. GIS is useful because it illustrates trends and demonstrates patterns, and enables query and analysis by linking tabular and spatial data. By using GIS it is possible to develop relationships between land use and water quality issues in the watershed. In using GIS it is possible to identify threats through a screening process and enables decision making to focus in on water quality hotspots. An example of the analysis completed indicated a relationship between high levels of sulfate in stream water and an abandoned gypsum mining operation.