NUTRIENT LOADING PATTERNS ON AN AGRICULTURALLY IMPACTED STREAM SYSTEM IN HUNTINGDON COUNTY PENNSYLVANIA OVER THREE SUMMERS

Spruce Creek and Warrior’s Mark Run, located in Huntingdon County of Central Pennsylvania, were studied from 2002 to 2004 to determine the effects of agricultural practices on water quality. These two creeks are tributaries to the Juniata River which feeds the Susquehanna River. The summers of 2002, 2003, and 2004 represent different hydrologic conditions of the Spruce Creek watershed, which allowed for testing of nutrient fluctuations under a variety of hydrologic conditions. Land use varies along the banks of these streams; a concentrated animal feeding operation is located near the banks of Spruce Creek, while Warrior’s Mark Run has much traditional agriculture located near its banks. Headwater samples of Warrior’s Mark Run contain low nitrate concentrations (0.44-0.89 mg/L), whereas the water samples from all other sampling sites have higher nitrate concentrations (>8.0 mg/L). Overall, the total nitrate loads are higher on Spruce Creek than Warrior’s Mark Run. Nitrate is present in the stream system regardless of the amount of rainfall, and tends to increase as discharge decreases. This could indicate that nitrate enters the system through baseflow. Within this stream system, phosphate behaves differently than nitrate. Generally, Spruce Creek exhibits a higher phosphate load than Warrior’s Mark Run. Phosphate concentrations seen in the headwaters of Warrior’s Mark Run are similar to the other sampling locations along this stream, indicating that the bedrock is potentially a source for this nutrient. In contrast to nitrate concentrations, the phosphate concentrations increased during large discharge events. This signifies that phosphate is likely associated with particulates derived from surface runoff due to rain events. Turbidity typically increases with elevated discharge, as well as with increases in phosphate levels. This suggests that an input of phosphate into the stream system may be associated with an input of particulates, which will raise turbidity. Conversely, nitrate concentrations vary with increasing turbidity.