Three years of continuous records of net radiation Rn were taken over a pine forest, a cienega, and a clear-cut opening. Seasonal patterns of the portion of Rn going into evapotranspiration ET were determined for these cover types by energy budget measurements in the Bowen ratio equation. By using the average daily Rn over two summer periods (May to June and July to September) and the mean ratios of ET to Rn, ET for the three cover types for the growing season was estimated at 19.4 in. for the forest, 15.3 in. for the clear-cut opening and 13.2 in. for the cienega. Weighting these amounts by the extent of the type resulted in a watershed average ET of 18.4 in. for the growing season.