New report warns of threats to metro Phoenix groundwater
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A new report from Arizona State University’s Kyl Center for Water Policy warns the groundwater supply in the Phoenix area faces some major threats in the years ahead.
Water portfolios vary widely city-by-city, but about a third of water used across the Valley is groundwater. Other water comes from the Colorado River, the Salt and Verde Rivers, and reclaimed water.
The Groundwater Protection in the Valley of the Sun Past, Present, and Future report notes Arizona’s water laws have been successful in protecting the Valley's finite underground water supply from the worst outcomes.
"Because of the 1980 Arizona Groundwater Management Act, the Valley is one of the few highly populated arid or semi-arid areas in the world where groundwater stocks are not currently in steep decline," the report's authors write.
But the report goes on to say the rules for replenishing groundwater laid out in the Groundwater Management Act aren’t perfect. The authors point out when Valley cities pump groundwater in their area, they are not required to recharge the aquifer in the same place. So supply is being depleted in some areas faster than others.
"Unless aquifer recharge and replenishment occur closer to areas of groundwater decline, the aquifer in these areas will likely be lost — meaning that aquifer layers will subside and compact," the report says.
Colorado River shortages will make this worse as users rely more on wells and have less river water available to replenish the aquifer, the report projects.
The report urges investment in infrastructure to allow groundwater to be recharged more evenly across the Valley and to allow some groundwater-dependent communities to use more water from other sources.
"This transition is likely to be extraordinarily costly," authors write, but they add, "the longer these infrastructure investments are delayed the bigger the problem for future generations."
