Implications of Rosemont Copper Mine on medium- and long-term water balance in Arizona: Dynamic modeling under different climate and economic scenarios
The operation of large mines, such as Rosemont Mine, in water scarce region of Arizona has the potential to alter the water demand and supply in the region. While Rosemont Copper has been permitted by the Arizona Department of Water Resources (ADWR) to pump up to 6,000 acre-feet of water per year, there are multiple conflicting factors that concerns the long-term water balance in the region with the construction of the Rosemont mine. Already, the other large mines in that region, mainly the Sierrita and Mission mines, have pumped between 18,299 and 28,492 acre-feet from 2000 to 2008. The mining company argue that will replace the aquifer water with Central Arizona Project (CAP) water, however, they have not secured CAP guarantee for the full life of the mine. In addition, though the Rosemont mine proposes to have small water footprint compared to other mining operations in the country, when we consider the water demand at the system level (watershed level or sub-basin level) the large industry (including all the big mining industries in the area) can have significant implications on water balance at the sub-basin level. And the situation can go worse when there are prolonged drought events that are common in semi-arid regions. This study takes the system’s perspective (watershed level perspective) and focuses to under the the direct and indirect water footprints of Rosemont Mine over the multi-decadal time scale at the sub-basin level. The study will conduct a dynamic modeling of long-term water footprint of the Rosemont mine at sub-basin level and explore multiple scenarios. The scenarios include (i) extreme drought within the span of 40 years, (ii) simultaneous water demand in large mining operations in Green Valley, (ii) simultaneous growth over 40 years period in different sectors including residential and other sectors, and (iii) impact of job growth on residential water demand. Such study will lead to better understanding of the longer term effect of Rosemont mine on the long term water sustainability in the water scarce region.