The Oak Orchard Soil Water Assessment Tool: Part 2

Abstract

Soil Water Assessment Tool, calibrated to two years of observed flow, sediment and phosphorus data, was used to evaluate flux changes along the main channel of the Oak Orchard River. The model employed realistic crop rotation and nutrient management scenarios, incorporates inputs from all point sources, and includes groundwater inputs from the Onondaga escarpment. The model suggests that significant amounts of sediment are sequestered in reaches containing the Iroquois National Wildlife Refuge and the Glendale dam. Some sequestering of sediment also occurred behind the Waterport dam and the reach immediately downstream. A significant increase in sediment loading occurred in the reach between the Glendale dam and River road. Inputs along this reach should be considered a management priority, as downstream sequestration in at least one of the crop scenarios was unable to reduce the flux of sediment to its pre-Glendale Dam levels. Fluxes were found to be a strong function of climate, with wet winters producing the greatest fluxes of sediment and phosphorus, followed by average conditions, wet falls, wet springs and wet summers. Fluxes were also found to be a strong function of crop location. Low phosphorus fertilizer strategies did not significantly reduce the amount of total phosphorous produced. Reductions in mineral phosphorus exports were noted, however these decreases were associated with increases in organic phosphorus exports. The location of crops on specific hydrologic response units proved to have a much larger effect on phosphorus exports. Total phosphorus was not observed to be sequestered anywhere in the main channel. These results are caused by the ratio of organic to mineral phosphorus predicted by the model, which is very large. The model shows large increases in phosphorus fluxes occurring in the Mucklands and the stretch of the river between Glendale Dam and River Rd. A flux balance analysis of the harbor shows that Oak Orchard river is the dominant source of phosphorus, contributing between 85% and 95% of the total flux. Based on these simulations, average yearly fluxes of sediment and total phosphorus out of the harbor are 7,550 and 103 tons per year.