ANNUAL HYDROLOGIC RESPONSE TO WATERSHED CONVERSION FROM OAK WOODLAND TO ANNUAL GRASSLAND

A 12‐acre experimental watershed in the Sierra Nevada foothills of central California has been subjected to intensive range management practices after a six‐year calibration. The treatment consisted of chemically killing a dense stand of oak trees and brush to improve forage production. An adjacent untreated watershed, which is geologically and hydrologically similar, provides a means of evaluating the annual hydrologie response. Streamflow comparison shows an average annual increase of 4.5 inches in water yield. Inflow‐outflow analysis shows a corresponding decrease in consumptive use from an average of 20 inches per year to 15 inches per year. The change in consumptive use is demonstrated in an annual water yield prediction model and in the relationship of consumptive use to precipitation. Estimates of annual potential evapotranspiration from climatological data are higher than measured consumptive use. Two methods for predicting annual consumptive use show close agreement with measured values for both the oak woodland and the annual grassland. Copyright 1968 by the American Geophysical Union.