Evaluation of a rangeland model
A large amount of water is lost on rangelands due to the conditions of the watersheds, specifically due to the presence of plant species with a high transpiration rate. Vegetation manipulation and watershed management have been proposed as means to increase water yield. Increasing efforts have focused on developing management practices and tools to evaluate the potential for increased water yield. Hydrologic modeling plays a key role in these efforts, and one the most comprehensive tools for simulating rangelands is the SPUR model. However, some limitations seem arise from the use of the SCS curve number method for simulating the runoff/infiltration process. In this project, the SCS curve number method was replaced by the Green and Ampt infiltration equation. One of the major advantages of the approach is that it relies on rainfall intensity rather than on daily rainfall, and it uses physical parameters such as the saturated hydraulic conductivity. The original and the modified SPUR models were tested for three different covers: bare, grass and mesquite. The use of the Green and Ampt infiltration equations improved model prediction of surface runoff. Furthermore, the model was shown to be sensitive to vegetation manipulation, and could be used as a water resources management tool.