Elevated Bacteria and Nutrients in an Urban Creek during Wet Season Baseflow

HARBESON 30

In arid regions, flushing of pollutants from diverse sources during storm events may influence water quality. This effect is important because it increases the transport of contaminants into coastal areas, which is a public health concern, and can result in beach closure. We conducted year-long sampling in the Upper Reach of Alvarado Creek during wet and dry seasons. We tracked changes in fecal indicator bacteria concentrations using IDEXX Colilert and Enterolert systems. Our results showed that E.Coli concentrations increased substantially, up to an average of 434 MPN/100 mL, in baseflow during the months of December through February. Furthermore, total dissolved nitrogen was seen to increase during these months possibly due to run-off of nutrients from lawns and other sources in the watershed. Conductivity, which is an indirect measure of salinity in water, also indicated that the creek is brackish, which affects many aquatic organisms. The focus of this research on water quality during baseflow is important because it serves as a baseline for comparison with water quality during storm events, that can better aid us in understanding the magnitude of pollution inputs in Alvarado Creek.