WATER QUALITY IMPACTS DUE TO AGRICULTURE AND URBAN RUNOFF IN THE MIDDLE PROVO RIVER, UTAH

Understanding the impact of population growth and urban development on the water quality is an important issue, especially in the rapidly growing arid states like Utah. The purpose of this study is to evaluate water chemistry in the middle Provo River system, which flows through Heber Valley, in the Wasatch Mountains of central Utah, and is undergoing a rapid transition from agriculture- to urban-dominated landscape. The study focuses on quantifying trace element and nutrient concentrations and salinity in storm runoff, snowmelt, and irrigation return flow. Samples were collected seasonally during 2014 to evaluate water chemistry during runoff and baseflow conditions.

Preliminary results show that concentrations of a variety of trace metals and salts increase at least two-fold along a short stretch of river that flows through Heber City. Several metals are strongly correlated with conductivity with r²>0.9, including, Ca, Na, Sr, and K, indicating that they were easily explained by the variable conductivity. Other metals, including B, Mg, Li, Rb, Cs, Ni, As, and Co, had r²>0.7, and could be moderately explained by the variation in conductivity. Unexpectedly, we found a 10-fold increase in Mn within a small stream running next to a waste water treatment plant, suggesting that this relatively slower stream loses dissolved oxygen and causes reductive dissolution of Mn-oxides. Snake Creek, which feeds into the middle Provo from the west side of the valley, was of particular interest due to consistently higher concentrations of As, Sr, Rb, Mo, Cs, Tl, B, Li, K, Na, Mg, and Ca relative to the Provo River and other tributaries. Arsenic concentrations in Snake Creek were 2.5 to 4.5 times greater than any other site in the valley. Multiple hot springs and thermal groundwater most likely contributed metals to Snake Creek. Shallow groundwater samples from springs and wells were compared to determine a representative groundwater trace element and nutrient chemistry. With concentration and flow data, we estimated loads from each source and their effect on the river. Using the representative groundwater concentrations, we estimated the flow of groundwater within a specific reach. Knowing what each source contributes to the river will help develop methods of mitigation and control for future water quality in urbanizing areas.