The Cottonwood Creek study area in the Redding basin, California , contains a network of wells established to provide baseline information on ground-water levels and quality prior to the completion of two proposed dams, one on Cottonwood Creek and one on South Fork Cottonwood Creek. Analysis of monthly ground-water levels from September 1982 through September 1983 shows lowest water levels in autumn and highest in spring. The ground-water surface slopes east and has a mound at Anderson-Cottonwood Irrigation District Canal near the town of Cottonwood. Future studies here could provide additional information needed for subsequent modeling studies. Data are insufficient upstream from the damsites, specifically in areas of future impoundment where the monitoring network could be expanded. Comparison of ground-water quality samples collected from periods of lowest and highest water levels showed little chemical variation. Ground water is good to excellent with respect to recommended drinking-water standards. Ground-water types north of Cottonwood Creek are sodium magnesium or magnesium sodium bicarbonate and south of Cottonwood Creek are calcium magnesium or magnesium calcium bicarbonate. Surface-water samples from Cottonwood and South Fork Cottonwood Creeks indicate water chemically similar to ground water south of Cottonwood Creek. (USGS)
