NITRATE ANALYSIS OF WATERS IN THE WINTER CREEK WATERSHED, SAN GABRIEL MOUNTAINS, CALIFORNIA

Water quality is fundamental for proper resource management, healthy ecosystems, and sustainable human use. The Winter Creek Watershed within the San Gabriel Mountains above Sierra Madre, has frequent recreational use and is managed for flood control and water quality. Yet, there is little data publicly available water quality data to assess potential environmental and human health risks. Cal Poly Pomona student, Greg Van Oosbree (2012), analyzed several water samples with 300 mg/L of nitrate, far exceeding the Environmental Protection Agency (EPA) Primary Standard of 10 mg/L. To address this knowledge gap and understand nitrate sources in the watershed, a nearly year-long study investigating basic water quality parameters throughout the watershed was completed from February 2014 through December 2014. Done by checking pH, conductivity, and stream flow at each location along with filtering water samples to be analyzed back in the lab. Sampling was also concentrated near a campground with open pit toilets up-gradient in the watershed (hypothesized source). Nitrate concentrations in all samples ranged from below detection to 13.96 mg/L. One sample location, a spring in the middle of the watershed, had very consistent nitrate that ranged between 11.24 and 13.96 mg/L across the entire sampling period. Though this sample location (this study) is above the EPA limit, it is still far less than the 2012 high nitrate sample (~ 300 mg/L, Van Oosbree). Interestingly, there appears to be no indication based on this dataset that the campground is a source of high nitrate. A deeper water system is now hypothesized to be the nitrate source. However, further study is warranted.