Gravel Mulch Buffers

Water quality and soil erosion are high priority issues for U.S. agriculture. In more humid areas of theU.S., vegetation filter strips have proven to be an effective method of reducing erosion and improvingwater quality. Filter strips are less effective in the West due to sparser vegetation and more variablerainfall. In addition, establishment of vegetation is more difficult in many western watersheds due tolower soil water availability. To address this problem, we propose gravel mulching of upper reaches ofarroyos. Gravel mulching will increase recharge and moderate the watershed hydrograph. Thesemoderating effects are due to the interception of runoff and the reduction of evaporation andtranspiration on the shoulder of the arroyo. Lateral water movement to the channel increases wateravailable for plant growth and bank stabilization. Part of the water will travel vertically and rechargethe water table. The magnitudes of these processes require quantification. The soil water profile andsedimentation will be monitored over time. These data, coupled with a modeling exercise, will be usedto quantify recharge and to partition it into vertical and lateral components. The results of theseanalyses are then used for optimizing a site-specific design.