Effects of Precipitation on Nonpoint Source of Alkaline Earth Element Contamination to Surface Waters in the US Great Plains

Abstract

Declining surface water quality is of great concern across the Great Plains. Recent changes in the earth’s climate can create abrupt changes in domestic weather that can alter the impact of nonpoint sources on water quality. A 2-year study (dry and wet years) was conducted to assess the impact of annual precipitation and runoff on water quality. Both dissolved and sediment-bound forms of alkaline earth elements (calcium (Ca), magnesium (Mg), potassium (K), barium (Ba), and strontium (Sr)) were determined weekly in runoff. Dissolved forms accounted for most of the element contents in runoff. The average concentrations of dissolved Ca, Mg, K, Ba, and Sr in runoff during the dry year (104, 24, 7.6, 0.38, and 0.61 mg/L, respectively) were greater than those during the wet year (65, 15.5, 7.2, 0.19, and 0.37 mg/L, respectively). On the contrary, the annual element loadings in surface water were greater for the wet year than those during the dry year. Calcium contributed to the greatest loadings (920 and 2,234 metric tons for the dry and wet years, respectively), whereas Ba had the least loadings at 3.7 metric tons for the dry year and 12.3 metric tons for the wet year. We concluded that greater precipitation during the wet year increased the negative impact of runoff alkaline earth elements on water quality in the Great Plains.