No Name Creek valley is a trough cut in granitic bedrock in north-central Washington. A low topographic divide in the northern third of the valley separates it into the No Name Creek basin on the south and Omak Creek basin on the north. Omak Creek is the larger stream and enters the valley through a narrow gorge in the eastern granite wall. Partly filled with unconsolidated sand, gravel, and silt to depths as great as 163 feet, the valley contains a ground-water reservoir which supplies four irrigation wells and several domestic-supply wells. The ground-water reservoir also feeds springs which give rise to No Name Creek, and it contributes some water to Omak Creek to the north. Under conditions of the pre-1976 development the ground-water divide was naturally about 3,000 feet north of Omak Creek gorge, and about 580 acre-feet of leakage from Omak Creek recharges the No Name Creek ground-water reservoir. By 1977, ground-water withdrawal of 994 acre-feet per year in No Name Creek basin had caused the ground-water divide to shift to a position about 4,000 feet north of the topographic divide. This increased the drainage area contributing to the No Name Creek ground-water reservoir for about three months so that during a year of normal flow a total of about 600 acre-feet of leakage from Omak Creek can be captured. It is postulated that as much as 1,100 acre-feet per year can be pumped in the central part of the reservoir. This pumpage would cause the ground-water divide to shift farther north, resulting in the capture of additional recharge from Omak Creek; the total leakage would be about 700 acre-feet per year. (Woodard-USGS)