Nutrient pollution continues to threaten water bodies and, in many places, appears to be getting worse despite gains that were made decades ago with the regulation of point sources under the Clean Water Act. Excess nutrient loads from agricultural non-point sources are largely unregulated, yet their contribution often outweighs that of other sources in many U.S. watersheds. This translates to a need for nutrient management strategies that go beyond traditional regulatory options. USEPA has used the Upper East Fork of the Little Miami River Watershed, a 192,000-acre mixed-use system in Southwestern Ohio, as an economics case study for over a decade. Both temporary and long-term monitoring stations assess sources, fluxes, and fates of nutrients in the system. These data support the parameterization, calibration, validation, evaluation, and application of a watershed nutrient loading model that tracks the fluxes of nutrients from edge-of-field and pipe-level sources to the masses loaded to a reservoir used for drinking water and recreation. The reservoir is plagued by harmful algae. We provide prescriptive monitoring and modeling to understand the feasibility of using water quality trading (WQT) as an approach to meeting total phosphorus (TP) and nitrogen (TN) reduction goals set for the system.
Results/Conclusions
TP and TN targets for the streams draining to the reservoir were set at 60 and 700 ppb, respectively, which given current conditions would require ~90,000 and 900,000 kg/yr of removal at costs of $3.6–$8.0 million for TP and $6.7–$14.5 million for TN. Point sources are responsible for <2% of these costs, while the rest must come from mitigating 104,000 acres of row crops. If fertilizer application rates remain static, the required mitigation cannot be met by one type of best management practice (BMP). The TP reduction alone equates to about 20% of annual net income from row crops, and would require about 1000 acres of constructed wetlands, 2600 acres of filter strips, and 41% of fields to use cover crops. We research the practicality of this mitigation effort, the incentives among potential participants in a WQT market and are working directly with farmers through the Conservation Districts to increase adoption rates of nutrient management practices. While the strides in BMP implementation have been remarkable over the last 5yrs, the overall economic prospects suggest a desperate need for innovative and more cost effective nutrient reduction strategies.