Nutrient Loadings Into Conesus Lake

Abstract

A nutrient loading study utilizing field measurements has not been performed on Conesus Lake tributaries since the construction of a perimeter sewer. The database from this study includes many parameters and is quite large. This report details the results of measurements for stream nutrient loadings, effects of the Inlet wetland on nutrient dynamics and road salt loadings. N0 3 -N loading upstream of the Conesus Inlet Wetland that was consistently about 2.5 times higher than downstream suggests nitrogen removal by denitrification in the wetland. Hanna's and Wilkins Creeks were found to be sources of high sodium and chloride loadings on an areal basis (kgjha). A statistically significant multiple regression (r 2 = 0.51, p = 0.001) was found which describes decreasing temperature, increasing precipitation and increased sodium loadings during the winter months, November to March. Soluble reactive phosphorus (SRP) and nitrate-nitrite nitrogen (N03 -N) loadings of 2,444 kg and 47,870 kg, respectively, were estimated for eight tributaries to Conesus Lake for the period April 1985 March 1986. Intense precipitation in November 1985 and the March 1986 snowmelt resulted in these two months combining for 72% of the total SRP load and 65% of the total N0 3 -N load. Two streams located in the northwest quadrant of the watershed, (Long Point Gully and Hanna's Creek) were identified as major sources of nutrient 1 oads, combining for 41% of the total SRP load and 40% of the total N0 3 -N load. Collectively, the northern streams exported about twice as much N0 3 -N ·and SRP than the southern streams. This suggests that remedial efforts for decreasing nutrient loss from the Conesus Lake watershed should be aimed toward the northern streams in general, and Hanna's and Long Point in particular. A strong, direct relationship between stream nutrient load and the percent of the watershed in cropland has been found. This has implications for watershed management if there is a desire to mitigate the nutrient load from the tributaries. Fertilization practices could become more conservative, crops requiring less fertilizer could be grown, and strategies to decrease direct runoff are discussed and could be implemented.