Efficacy of Source Water Protection for Reducing Costs of Drinking Water Treatment

In the face of threats to source water quality such as population growth, land use change, and intensive agriculture, utility managers at drinking water treatment plants must allocate resources between increased treatment at the plant and promotion of best management practices (BMPs) in the watershed. While source water protection makes intuitive sense, the costs and benefits of such programs for the water treatment plant (WTP) are in most cases unknown. This paper uses a loosely-coupled watershed-water treatment plant modeling technique to provide a screening-level assessment of: (1) the impacts of major point and nonpoint source pollutant loads on WTP operating costs; (2) the potential of agricultural and urban BMPs and best available technologies (BATs) to mitigate these impacts; (3) the cost-effectiveness of BATs and BMPs in the watershed vs. increased treatment at the WTP. A screening-level watershed model was used to quantify changes in annual suspended solids and organic carbon loads exported under varying land use and BMP implementation scenarios, and a dynamic water treatment plant model was used to quantify the impact of associated changes in daily raw water quality profiles on water treatment plant operations and costs. National data on the ratio of catchment size to WTP size was used to determine the fraction of utilities that may benefit from BMP promotion.