Water Quality Changes Shortly After Low-Head Dam Removal Examined With Cultural and Microbial Source Tracking Methods

Short-term effects of low head dam removal on water quality of urbanized stream were evaluated, focusing on fecal pollution indicators. Composite river samples were analyzed for Escherichia coli concentrations, nitrates, phosphates, turbidity and human-specific marker (HF183) and antibiotic resistance marker (tetQ) before and after dam removal during dry weather conditions. The sampled Olentangy River water in summer before the dam removal showed poor water quality with mean E. coli concentration of 439 colony forming unit (CFU)/100mL, mean turbidity of 10 NTU and mean nutrient concentrations of 0.61 and 0.41mg/L for nitrate and phosphate, respectively. Surprisingly, even one month after the dam removal, E. coli numbers doubled and nitrate concentration tripled compared to pre-removal concentrations. Although the detected HF183 concentrations were below the quantifiable levels, they did not correlate with E. coli concentrations, suggesting E. coli from other than human fecal origin. The correlation between turbidity and E. coli during dry weather further suggests E. coli accumulation in impoundment sediments and release once dam was removed. These short-term effects of dam removal on water quality should be further evaluated, especially if recreation and other beneficial uses of water in the area are expected. Copyright (c) 2016 John Wiley & Sons, Ltd.