Monitoring of coal mine operations on Black Mesa, Ariz., was started in 1971 to determine the effects of strip mining on water resources in the area. Monitoring on and near the mesa includes measurements of ground-water levels and quality and quantity, sediment concentration, and chemical quality of surface water. The surface-water monitoring consists of: (1) rainfall-runoff characteristics near the mine, and (2) surface-flow conditions and water-quality characteristics at Moenkopi Wash at Moenkopi. Three watersheds of about 400 acres each are instrumented for the collection of flow data, precipitation data, and water samples for determination of chemical quality and sediment concentration. Each watershed is equipped with a data-collection platform that transmits data via satellite to a computer that provides near-real time information ground-water withdrawal on the regional potentiometric surface in the aquifer on a continuing basis. The available data are insufficient to assess the effects of mining on the quantity , sediment concentration, or chemical quality of runoff. Water levels in seven wells have not shown significant declines but water levels in other wells have declined as much as 7 feet. (Woodard-USGS)