Abstract

In Niagara County, nutrient and toxic substance loads associated with sediment erosion and surface runoff from agricultural and urban land uses were listed as major countywide concerns (Niagara County Water Quality Committee, 1992). The focus area of this study was the Cayuga Creek watershed, located in Niagara County, New York. This is considered a mixed land use watershed but it predominantly consists of agricultural land with interspersed residential areas and an urban center at the confluence of Cayuga Creek and the Niagara River. The Cayuga Creek watershed has the same water quality issues as Niagara County, but as a result of the watershed’s land use further emphasis must be placed on sediment erosion and nonpoint source (NPS) pollution from agricultural land use.

The United States Environmental Protection Agency (USEPA) ad-dresses sediment erosion and NPS pollution issues collectively in Section 303(d) of the Clean Water Act, which requires individual states to implement a total maximum daily load (TMDL) plan (Santhi et al., 2001; Santhi et al., 2006). A TMDL plan establishes the load capacity of a water body, as well as the sources and amounts of pol-lutants that have to be reduced to meet water quality standards. After a TMDL plan is established, often best management practices (BMPs) are used to reduce sediment erosion and NPS pollution associated with surface runoff (Bracmort et al., 2006).

Watershed modeling can be used to assist in the implementation and evaluation of BMP scenarios by allowing for a better under-standing of the relationship between land use, land management activities, and water quality processes occurring within a watershed (Im et al., 2003). The amended Water Resources Development Act of 1996, Section 516(e), gives state and local officials the authority to evaluate and implement such water resource conservation projects. The USEPA recommends that state and local officials use a suite of models available in the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) framework to assess water resource conservation projects. The soil and water assessment tool (SWAT) has been used in national studies as well as regional 516(e) studies to asses BMPs and TMDL plans, and is one of the models included in BASINS (Di Luzio et al. 2002).

In the specific case of Cayuga Creek, early coordination with stakeholders making up the Cayuga Creek Watershed Management Committee (including Buffalo Niagara Riverkeeper, USDA Natural Resources Conservation Service, US Army Corps of Engineers, Buf-falo District, U.S. Fish and Wildlife Service, New York State Department of Environmental Conservation, Niagara County Soil and Water Conservation District [NCSWCD], Town of Niagara, Town of Lewiston, Council of Chiefs, The Tuscarora Nation, Buffalo State Col-lege, Cornell Cooperative Extension, and Niagara University) was made in an effort to ensure that the sediment transport model better reflected stakeholder expectations for the application of BMPs in the watershed. In particular, it was noted by Buffalo Niagara Riverkeeper that they would like a tool or tools by which they could assess impact from change in land use. BASINS SWAT was selected for use in this project because it has been used for work in other local watersheds (e.g. Inamdar and Naumov, 2006), and personnel at the NCSWCD office have some experience with BASINS SWAT applications for the 18-Mile Creek watershed. The SWAT model is also being used for a 516(e) study of the Cuyahoga River, Ohio, and as such there will be some consistency across multiple 516(e) projects.

The SWAT model calibration and validation procedures were done using flow, turbidity and total suspended solids (TSS) data col-lected at two sites in Cayuga Creek. Rating curves between flow and depth and between TSS and turbidity were established, which will also assist in future data collection efforts. The establishment of such procedures is pertinent because past collection efforts of TSS and flow data within the watershed have been scarce (URS Corporation and Gomez and Sullivan, 2005). Furthermore, the model will serve as a basis to build upon, as well as a framework to catalog future water quality data that can be used for a more accurate model calibration.

Land Use Land Cover (LULC) maps for 2005 and 1958 were de-veloped for the watershed as part of the development of the SWAT model. These LULCs will aid state and local agencies in assessing present and historical distribution of land use, as a first step in as-sessing how changing land use might impact water quality.

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