Calculating the Cost of Reducing Erosion from a Small Rangeland Watershed

Sediment is an important pollutant in the United States. Attempts to control sediment are under consideration for water bodies where sediment-affected water does not support designated uses. To be economically efficient, policies to control sediment should achieve required reductions in sediment at least cost. On rangelands, quantifying the scope of sediment reduction available through land management is problematic given the difficulty in quantifying sediment detachment, transport and deposition processes, and watershed runoff and sediment yield. As many ranches are economically stressed, imposing additional costs to reduce sediment could drive some ranchers out of business. A constrained optimization model was built that simulates the effect of imposing a constraint to reduce watershed sediment yield. The model calculates a rancher’s net return subject to technology and soil detachment and sediment yield constraints. By varying the sediment constraints and solving the model multiple times, an abatement cost curve can be estimated. A case study of the Walnut Gulch Experimental Watershed is examined in which the entire watershed is modeled as a single ranch. Results indicate little scope to significantly reduce erosion by reducing herd numbers in the short run. Although additional research is needed to quantify the effects of management on the vegetation community and sediment yields, automated methods to calculate abatement cost curves could improve rangeland water quality decision-making