Water-Quality Characterization of Subbasins in the Onondaga Lake Basin, Onondaga County, New York, by Land Type

Problem - The Onondaga Lake Partnership (OLP) is committed to improving the water quality of Onondaga Lake. Onondaga County Soil and Water Conservation District (SWCD) has promoted best-management practices to decrease loads of nutrients and sediment from agricultural lands. Onondaga County Department of Water Environment Protection has abated many of the outflows from combined sanitary-and-storm sewers in the city of Syracuse and has upgraded treatment capabilities for removal of nutrients in effluent from the county's Metropolitan waste-water-treatment plant. These measures have fallen short of target levels of phosphorus and nitrogen loadings to Onondaga Lake because of inputs from nonpoint sources of pollution. In 2005, the U.S. Geological Survey began a 3-year project to assess the water quality in flows from selected subbasins in the watershed and to characterize water quality on the basis of the dominant land use in each of these subbasins.

Objectives - The objectives of this project are to collect streamflow, suspended sediment, nitrogen, and phosphorus data to (1) identify the effects of land use, land cover, and slope on water quality; (2) upgrade a precipitation-runoff model of the Onondaga Lake basin-currently being developed by the USGS-with loading rates that are basin specific rather than estimated from literature values; (3) compare concentrations and loads with those measured during 1982-83 in three tributaries to Otisco Lake and assess the effects of best-management practices on loads from agricultural areas; (4) quantify the sediment loads to Onondaga Creek from the Mudboils (a ground-water source of fine-grained sediment), Rainbow Creek, and Rattlesnake Gulf; (5) document the changes in the water quality from headwater areas to the mouths of the two major tributaries in the Onondaga Lake basin-Onondaga and Ninemile Creeks; (6) quantify the mitigative water-quality effects of Onondaga Reservoir and Otisco Lake; (7) assess the effects of ground-water discharges on surface-water quality; (8) compare suspended-sediment and total-suspended-solids concentrations at four sites in the Onondaga County Ambient Monitoring Program; and (9) provide data to assist water-resources managers in the development of watershed management plans and total-maximum-daily-load (TMDL) allocations to Onondaga Lake.

Benefits - The concentration and loading data compiled through this project will meet the multiple needs as listed above, but ultimately will provide essential data that can be used by water-resources managers to identify nonpoint-pollution sources and make decisions regarding the mitigative measures that are likely to decrease the loads that are currently entering Onondaga Lake. These steps will move OLP closer to the court-mandated improvements in the water quality of Onondaga Lake. The study will benefit Federal priorities by (1) providing the data to better define and manage the quality of the Nation's water resources, (2) advancing knowledge of the regional geohydrologic system, (3) contributing data to national databases that will be used to advance the understanding of regional and temporal variations in hydrologic systems, and (4) providing water-resources information that will be used by multiple parties for planning and operational purposes.

Onondaga County, NY