Water quality and soil erosion are high priority issues for U.S. agriculture. In more humid areas of the U.S., vegetation filter strips have proven to be an effective method of reducing erosion and improving water quality. Filter strips are less effective in the West due to sparser vegetation and more variable rainfall. In addition, establishment of vegetation is more difficult in many western watersheds due to lower soil water availability. To address this problem, we propose gravel mulching of upper reaches of arroyos. Gravel mulching will increase recharge and moderate the watershed hydrograph. These moderating effects are due to the interception of runoff and the reduction of evaporation and transpiration on the shoulder of the arroyo. Lateral water movement to the channel increases water available for plant growth and bank stabilization. Part of the water will travel vertically and recharge the water table. The magnitudes of these processes require quantification. The soil water profile and sedimentation will be monitored over time. These data, coupled with a modeling exercise, will be used to quantify recharge and to partition it into vertical and lateral components. The results of these analyses are then used for optimizing a site-specific design.Applications:Anticipated results include a large increase in recharge, reduction of soil erosion, and improvement of water quality in watersheds with ephemeral and intermittent tributaries characteristic of the western U.S. These effects (especially increase in recharge) are of direct financial benefit to private landowners. Because this project focuses on the more neglected subsurface flow component of watershed management, the results also benefit watershed managers who now generally lack tools to integrate subsurface and surface water flow into an effective management plan.
