Monitoring activities of coal mine operations on Black Mesa were started in 1971 for the purpose of monitoring the effects of strip mining on the water resources of the area. Black Mesa is located in northeastern Arizona near the center of the Navajo Indian Reservation and is a prominent topographic high about 500 to 1,000 feet above the surrounding area. Monitoring on and near the mesa consists of measurements of ground-water levels, ground-water quality, and measurements of the quantity, sediment concentration, and chemical quality of surface water.
The surface-water monitoring consists of: (1) rainfall-runoff characteristics in the immediate vicinity of the mine, and (2) surface-flow conditions and water-quality characteristics at a site on Moenkopi Wash at the village of Moenkopi.
Three small 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 the data via satellite to a computer that in turn provides near-real time information on rainfall and runoff.
Available data at this time are insufficient to assess the effects of mining on the quantity, sediment concentration, or chemical quality of surface-water runoff.
Water levels in seven wells, measured annually, have not shown significant declines. The water levels in some of the other wells in the network have declined as much as 7 feet, and others have fluctuated in response to seasonal pumping by nearby wells.
