What is Safe Yield and Does it Actually Matter?

Arizona's Groundwater Management Act (GMA), the landmark legislation passed in 1980 intended to finally get groundwater pumping under control in the state, has a mandate that by 2025 groundwater mining (pumping out more that is replaced) should cease in the most populous parts of the state. The law also defined safe yield as the condition where water pumped out of the aquifer is in balance with water entering the aquifer, whether naturally or artificially. The law mentions artificial recharge specifically, reflecting an understanding that natural recharge to many aquifers in the state is very limited and must be augmented by adding water through specially constructed recharge facilities.

Does this mean that water tables in the state would stabilize when safe yield is reached? Not necessarily, because the safe yield concept applies over large areas, only requiring that there be a balance over those large areas – called Active Management Areas (AMA) – which, in reality, could mean that water levels could be continuing to drop precipitously in one part of an AMA but if that pumpage is offset by recharge in another area it's still kosher under the law. That is the precise situation that is currently occurring in the Tucson AMA (TAMA) and is one of the issues to be addressed by a recently created working group, called the Safe Yield Task Force. These specific problems are known as sub-area management issues.

This problem has been significantly exacerbated by the creation of the Central Arizona Groundwater Replenishment District (CAGRD). Many in the water field know of the CAGRD as the legislative acquiescence to the needs of the property development industry in Arizona – the one sector of state commerce not at the table when the GMA was being crafted. The less cynical view is that the CAGRD became necessary for the state to implement the Assured Water Supply rules that were necessary as part of the GMA – rules that required future development to rely on renewable water supplies (essentially Colorado River water via the Central Arizona Project (CAP)).

The CAGRD is an entity that acquires and recharges (replenishes) renewable water to offset the groundwater pumping of cities, towns, and subdivisions that enroll as members in the district. And because the GMA only requires that water use be in balance on an AMA-wide basis, there is no requirement that this pumpage be offset in a way that mitigates water level drawdown caused by that pumpage – i.e. the replenishment can, and often does, occur many miles away and down-gradient from where the groundwater was pumped.

While I would like to think that this Safe Yield Task Force will be able to tackle these sub-area management issues it's an issue that reaches too far into our local economies and involves several key entities who are probably less than enthusiastic about solving these issues (in the most rational and cost-efficient manner). In a nutshell, resolution involves a combination of infrastructure investment (extending renewable water to up-gradient areas for recharge or direct use) and regulatory restrictions on pumping in the most-affected areas (setting pumping limits and restricting new wells in areas where water declines are greatest and the cost of extending renewable water supplies is prohibitive). Property owners in the sub-areas with water supply problems don't want to be excessively restricted in their use of groundwater – they want taxpayers to subsidize the installation of infrastructure to offset their excessive pumping. Taxpayers don't want to subsidize expensive infrastructure to save the bacon of property developers who continue to insist on building in areas with limited water supplies, so they are ok with imposing restrictions on pumping.

As I'm an ongoing participant in the Task Force I will try to post updates on what is occurring there periodically.

Another issue that deserves a post in the next few days is the Draft Phase II Action Plan recently developed by the city and county staff charged with implementing the recommendations of the Phase II City/County Water Study report. There is currently an open comment period on the Action Plan until 10/7. I haven't decided yet if I will submit comments, but will be going over the Action Plan with the Phase II report this weekend to assess whether I should.