Water Quality Simulation and Economic Valuation of Riparian Land-Use Changes

Abstract

It is widely recognized that many agricultural watersheds are contaminated by nutrients and sediments. However, land-use change in the riparian corridor can be a viable option in mitigating the non-point source pollution. On the other hand, the water quality management strategy will be successful only if it is economically feasible. The research focus of this dissertation is to quantify the ecological and economical impacts of land-use changes in riparian buffer zones on the hydrology and water quality in the Little Miami River watershed, Ohio, through creation and application of an integrated modeling approach. The ArcView GIS based U.S. EPA BASINS/HSPF model was calibrated and validated from 1980-1993 using local DEM, climatic, land-use, flow, and water quality data. The replacement cost method was used to estimate the value of riparian forest buffer zones based on the cost of nitrogen and phosphorus removal through wastewater treatment plants. Results indicated that the 60-meter, 90-meter and 120-meter riparian forest and wetland buffers were able to reduce the mean annual flow by 0.26% - 0.28%, mean annual nitrite plus nitrate by 2.9% - 6.1%, and mean annual total phosphorus by 3.2% - 7.8%. It was also found that three engineering best management practices (BMPs) in the agricultural land, 25% filter strips, 50% filter strips, and 25% grassed swales, could achieve similar or better nutrient mitigation results than the riparian buffers. The economic valuation showed that for the 60-meter, 90-meter and 120-meter riparian forest buffers, the benefit:cost ratios were the same, 0.269:1. The highest benefit:cost ratio, 0.348:1, was from 50% filter strips. Although none of them was cost effective, compared with two selected engineering BMPs, the 60- meter forest buffers had the highest benefit:cost ratio among three riparian forest buffer designs. This dissertation has demonstrated that the BASINS/HSPF is a very reliable and useful water quality and quantity assessment tool, and the replacement cost valuation method is able to effectively estimate both the costs and benefits of riparian land-use changes.