Agricultural Water Supply from a Dewatered Mine – a Beneficial Partnership Where Scarcity and Abundance Meet.

Water scarcity is an increasing challenge for agriculture in the arid Western US, particularly for high water use crops such as alfalfa, an essential livestock feed crop. New Magma Irrigation and Drainage District (NMID) has been highly dependent on Colorado River water via the Central Arizona Project (CAP) for irrigation, enduring annual and seasonal fluctuations in supply. Resolution Copper Mining, LLC (RCM) is in the process of developing an underground mine next to a historic mine in central Arizona. To gather the required information needed to inform the future mine, a new shaft was constructed. Sinking a new shaft required removal of approximately 8,200 acre-feet of constituent rich water from the historical mine. Any beneficial use of this water would need some form of treatment. In 2009, RCM partnered with NMID, University of Arizona, and Land IQ, LLC to develop a water quality blending protocol and monitoring program to supply NMID with supplemental irrigation water. This includes a telemetered water quality monitoring system; soil and crop monitoring; and provides growers with access to data to foster trust and cooperation. A 27-mile pipeline delivers mine water to NMID, which is blended with CAP water, to provide irrigation for alfalfa, cotton, turf grass and winter small grains. Real time water quality data and daily water orders from NMID dictate discharge rates of treated mine water. An extensive sampling and analysis program on 6,500 acres provides soil and crop health as well as soil salinity data that is available to NMID growers online. Through this ongoing successful partnership, NMID is more resilient to water supply shortages, and RCM has been able to reuse water for high beneficial use within a protocol that ensures environmental and agronomic quality.