Mark Johnson & Jim Tripp
Water Woes II-Sustainable not Assured
Updated: Jul 11, 2021
Did you read the recent water articles in the Arizona Daily Star by Tony Davis? Lets take a look:
Article 1: Climate change could reduce groundwater supplies
This article discusses a new draft US Bureau of Reclamation Study that indicates climate change will reduce the amount of natural groundwater recharge in the Tucson Active Management Area (TAMA). The draft study predicts that groundwater overdraft will begin again in the 2040's and worsen in the 2050's with continued over-growth and warming temperatures.
Article 2: Tucson's water supply can survive 'worst case' CAP cuts, city official says
Here Tucson Water officials indicate they can survive with a 50% cut to its Central Arizona Project (CAP) Colorado River supply by making up the difference by pumping naturally recharged groundwater from the aquifer. Yet the scientists and USBR (see above) indicate that natural recharge may not be so solid. And there was no mention of how long Tucson Water could sustain a 50% cut.
The article mentions that Tucson Water has a Designated Assured Water Supply (100 Years). But it did not mention that the Assured Water Supply analysis allows groundwater withdrawals up to a 1,000' below ground surface and groundwater recharge can occur anywhere in TAMA, i.e. not necessarily at the location of pumping. The public water supply should be indefinitely SUSTAINABLE for human use and maintenance of riparian habitats, which require a stable, shallow water table, as shown below. To achieve a "100 Year Assured Supply" by allowing the mining of groundwater until it is unavailable to humans, plants, and animals is to pursue a policy of "Assured Depletion." This is Arizona's biggest water folly.
Who And What Are We To Believe?
As discussed in Know Your H2O X-Marana & Tucson Water, the current Tucson Water 50-Year Water Plan presents a different story. Figure 6.1 indicates that CAP supply (delivered and recharged) is good until about 2030. Beyond that, new additional renewable supplies will be needed along with depleting any water from storage. And these projections assume no reduction in CAP supply!
Time To Send Consistent Information & Collaborate
TAMA water purveyors and scientists need to collaborate, agree on the assumptions, present consistent factual information and develop a Comprehensive 50-Year Water Management for the entire region with input from the water users as recommended in Know Your H2O-XI Recommendations and Conclusions.
Tucson Water is initiating its One Water 2100 Plan and we urge all residents to sign up to learn and become part of the planning. But why not undertake a single water management plan for the entire region?