WATER QUALITY ASSESSMENT AND NUTRIENT LOADING OF THE GRASSE RIVER, ST. LAWRENCE COUNTY, NEW YORK

A water quality assessment of the Grasse River (St. Lawrence watershed, New York) is being conducted to analyze the impact of nutrient loading on water quality. Nutrient contamination in water is directly related to land use applications (e.g. agriculture); and negatively impacts water quality, aquatic life, and the public. Basic water quality parameters and nutrients (nitrogen, sulfates, and phosphates) were measured at multiple locations along the Grasse River. These results were compared to the site evaluations for stream erosion and sediment loading potential that utilized Sediment Transport Analysis and Regional Training (START) field reconnaissance sheets authorized by the US Army Corp of Engineers. Average values for the basic water quality parameters are as follows: pH = 8.2 ± 0.37, conductivity = 116.18 ± 9.49 μS, total dissolved solids = 81.8 ± 6.78 ppm, dissolved oxygen = 9.91 ± 0.82 mg/L, and turbidity = 1.32 ± 0.32 NTU. Average values for nutrients are as follows: nitrate = 1.42 ± 0.69 mg/L NO₃-N, nitrite = 2 ± 0.60 mg/L NO₂-, total phosphorus = 0.36 ± 0.16 mg/L PO₄^3-, orthophosphate = 0.07 ± 0.04 mg/L PO₄^3-, sulfates = 3.33 ± 1.72 mg/L SO₄^2-, apparent color = 46.18 ± 14.75 units, and true color = 31.73 ± 10.49 units. The pH, conductivity, total dissolved solids, dissolved oxygen, true and apparent color readings stayed consistent while moving down stream. Turbidity, nitrates, nitrites, phosphorus, and sulfates fluctuated up and down in value while moving downstream. The fluctuations could be due to the introduction of tributaries that increased discharge and diluted the water, introduction of more sediment and nutrients, and/or obstructions present in the river that may have potentially cause solids and nutrients to settle out. These factors are being assessed further. Five of the 14 sample locations were rated as having minor erosion potential (9 were normal) using the START rating sheets. Though minor sites have a higher potential than normal sites for erosion, the current data shows that minor sites do not have statistically significant higher levels of nutrient loading (p-values < 0.05 for ANOVA tests, a = 0.05) compared to normal sites at the time of testing. Overall, the water quality of the Grasse River is good to excellent, with possibly little-no contamination due to erosion.