The Sycamore Creek watershed is representative of many small watersheds in the Southwest where much of the streamflow originates in the mountainous areas and disappears rather quickly into the alluvial deposits adjacent to the mountains. Five years of .streamflow records from the Sycamore Creek watershed show that an average annual water yield of 6,110 acre-feet was obtained from the 165 square miles (105,000 acres) of the upper hard-rock mountain area, which receives an average annual precipitation of about 20 inches. Only a small percentage of the ,annual water yield, however, reaches the Verde River as surface flow over the 9-mile reach of the alluvial channel below the mountain front. Flows must be more ,than 200 cubic feet per second to reach the river; flows less than this rate disappear into the 1,ower alluvial area and are stored temporarily in the ground-Water reservoir : most of this water is released as ground-water discharge to the Verde River at a relatively constant rate of about 4,000 acre-feet per year. Evapotranspiration losses in the lower alluvial area are controlled by the depth of the water table and averaged about 1,500 acre-feet per year.