Field Trips: Granite Reef Underground Storage Project (GRUSP)
To store the excess Colorado River water that became available to Phoenix in the 1990s, the Salt River Project (SRP) partnered with six municipalities to construct the GRUSP. This large underground storage facility has recharged more than of 910,000 acre-feet (1,120 million cubic meters) of water since it began operating in May 1994. It lies within in the floodplain of the Salt River on the Salt River-Maricopa Indian Reservation. Water from the Colorado, the Salt, and the Verde Rivers, as well as reclaimed municipal water, is delivered to seven recharge basins that cover 217 acres (88 hectares). The site’s favorable geologic position at the edge of the Salt River Basin allows water to infiltrate rapidly into the underlying aquifer. Although the facility was permitted to accept 200,000 acre-feet (247 million cubic meters), only half of that volume can be stored because regulatory requirements limit groundwater mounding at a nearby landfill. The GRUSP is very cost effective. Construction costs amounted to 1.1 million dollars, and its operation and maintenance expenses are among the lowest in Arizona.
We will also visit the Granite Reef Dam, where water from both the Verde and Salt Rivers is diverted to the extensive SRP canal system and where the CAP aqueduct discharges Colorado River water for delivery to most of Phoenix’s treatment plants.
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