The Denver Metro area is fully contained within the South Platte Watershed and so, the South Platte River is highly impacted by urban runoff and stream modification. Elevated nutrient concentrations, pesticide residue, heavy metals contamination, bacterial presence, and excessive sediment loading have been observed in the river. Many residents enjoy water-related activities in the South Platte River including fishing, kayaking, and wadding. However, in most stretches of the river, recreation is limited due to high levels of bacteria and concerns about public health. This ongoing water quality monitoring project began in May 2015. Every two weeks, measurements of dissolved oxygen (DO), pH, temperature, biochemical oxygen demand (a proxy for bacterial load), and the concentrations of nitrate, phosphorus, and ammonium are taken every three miles along the river, beginning southwest of Denver where the river emerges from the mountains, and ending north of the city, near Brighton, CO. This poster will focus on the drivers of bacterial loading in the river.
Over all the study sites, biochemical oxygen demand was positively correlated with the concentration of nitrate and with water temperature. The interactions of water temperature * pH and water temperature * nitrate were also significant. It appears that if the city of Denver would like to increase the recreational and ecological value of its primary waterway, developing ways to reduce the presence of nitrate within the South Platte River would be an effective approach. Future work will focus on the identification of likely nitrate sources using geospatial software and groundtruthing.