MONITORING EFFECTS OF WILDFIRE MITIGATION TREATMENTS ON WATER BUDGET COMPONENTS: A PAIRED-BASIN STUDY IN THE SANTA FE RIVER WATERSHED, NEW MEXICO

A paired basin study in the Upper Santa Fe River watershed following forest restoration measured water budget components in a treated and untreated basin. The paired basin study is in ponderosa to mix-conifer forest in the southern Sangre de Cristo Mountains and was established to investigate questions that have arisen with regards to changes in the amount and timing of water yield following forest treatments. Precipitation, stream flow, soil moisture, chloride concentrations in precipitation and stream flow were measured to quantify the water budget components. While the study is ongoing, the results from seven years show a high degree of confidence in the techniques applied. Chloride concentrations in precipitation and stream flow are measured to estimate evapotranspiration and recharge for varying integration periods of chloride cycling. The total inflow from precipitation for each integration period minus the outflow of stream flow, evapotranspiration, recharge and soil moisture leaves a remainder of less than 1%, thus most of the water is accounted for. Based on the ratio of chloride in precipitation to the concentration in stream flow, evapotranspiration is estimated to be about 90 to 94 percent in the treated basin and 76 to 85 percent in the untreated basin for the four integration periods of the ongoing investigation. Recharge is estimated to range from 1 to 4.2 % in the treated basin and from 4.5 to 4.7 % in the control basin. Stream flow in the treated basin relative to the control basin appears to be decreasing following forest treatments. However, recharge may be increasing and the intensity of runoff appears to be reduced from pre-treatment to post-treatment conditions. With continued monitoring as the vegetation reestablishes to the desired “restored” condition, we will be able to track changes in the water budget.