Genesee River Watershed Project. Volume 5. Water Quality Analysis of the Canaseraga Creek Watershed Nutrient Concentration and Loading, Identification of Point and Nonpoint Sources of Pollution, Total Maximum Daily Load, and an Assessment of Management Practices using the Soil Water Assessment Tool (SWAT) Model. A report to the USDA.

Abstract

An assessment of the Canaseraga Creek watershed was undertaken to determine the nutrient and sediment contribution to the Lower Middle Main Stem of the Genesee River and to determine sources of nutrient and sediment loss geospatially within the Canaseraga Creek watershed. To accomplish this task, a multifaceted, integrated approach was taken by a combination of monitoring, segment analysis, and modeling (Soil and Water Assessment Tool). Thus, the river was monitored for discharge, water chemistry, and loss of nutrients and soil for an entire year (3 August 2010 to 14 February 2012) at the USGS stations at Shaker’s Crossing and Dansville, NY. The Canaseraga Creek Soil and Water Assessment Tool (CCSWAT) model was created, calibrated, and verified for discharge, sediment, and P loss using these data. Based on the measured loading data to a subbasin outlet and the SWAT model, segment analysis was performed on selected subwatersheds to determine sources of material loss. Together these two bodies of information, the total amount of nutrients, sediments, and bacteria lost from the watershed and the sources of these losses, served to direct watershed management. Lastly, the CCSWAT model was employed to test the effectiveness of Best Management Practices (BMPs) on land use and to determine the minimum potential P concentration expected in a forested Canaseraga Creek watershed. With approximately 76.7% of its phosphorus load from anthropogenic sources, the largest subbasin (88,578 ha) of the Genesee River, Canaseraga Creek, should be a high priority for water quality remediation. Reducing phosphorus loads from Canaseraga Creek into the Genesee River is an important step to reduce the impact that the Genesee River has on water quality in the nearshore zone of Lake Ontario. In general, nonpoint sources of agriculture were identified as the leading cause of phosphorus loss in Canaseraga Creek through segment analysis, determination of weekly and event water chemistry, and integration into the Soil and Water Assessment Tool (SWAT) model. Of the various BMPs simulated throughout the whole watershed, grassed waterways were the most effective in reducing TP loading (44.8% reduction) and reducing TP concentration (69.9 ?g P/L) at Shaker’s Crossing. But grassed waterways by themselves did not reach either of the target (45 and 65 ?g P/L) TP concentrations. Simulations combining grassed waterways with upgraded (tertiary) WWTPs foe the entire watershed resulted in a decreased P concentration of 49.7 ?g P/L at Shaker’s Crossing. This simulation suggested a 65 ?g P/L is a realistic target concentration and that the 45-?g P/L target may be met with more stringent BMPs. A less costly approach is to focus remediation to a smaller area known to deliver P to the streams. For example, by implementing grassed waterways in the impacted tributaries of Twomile and Buck Run Creeks and the Groveland Flats area, by implementing streambank stabilization in highly erodible main stem areas, and by upgrading WWTPs to tertiary treatment (Tributary Remediation 3), the CCSWAT model predicted a reduction in TP concentration from 104.3 to 71.6 ?g P/L.