Ripple effects of new water outlook

After three years and $400,000, Mohave County found that the rapid depletion of its groundwater ... isn’t quite as rapid as everyone thought.

And that has implications for other rural Arizona communities, which also are rapidly depleting a finite (and in some cases their only) water resource.

But the implications are probably not what you’d think.

The county and the city of Kingman pitched in to fund the Cadillac of groundwater studies, a model from the United States Geological Survey that can predict the impacts of various pumping and replenishment scenarios.

Though the model has not yet been publicly released, USGS said in an Oct. 19 presentation that based on water-use information the county supplied, groundwater levels should not be anywhere near the state’s 1,200-foot cutoff by 2080.

Instead, according to its modeling, the Mohave sub-basin that includes Kingman should be closer to 750 or 850 feet below land surface in 2080, while the Hualapai sub-basin, where most of the farming is, should be around 650 to 725 feet.

That’s a much rosier conclusion than the Arizona Department of Water Resources reached in a recent study, which predicted 1,200-foot depths by 2080 and was widely interpreted to mean that the area had only about 60 years of good, accessible water left.

But there’s a reason for such widely differing outlooks: Water use.

The USGS model uses significantly lower figures because fewer acres are growing water-intensive alfalfa now than when ADWR conducted its study. More farms in the area are now cultivating nuts — which can still be water-intensive, in that they need water yearround, but tend to use less than alfalfa.

The USGS model presumes that agricultural land doesn’t continue to expand, and that farmers will continue growing nuts and vegetables, not switch back to alfalfa should market conditions change.

If they do, water levels would drop precipitously.

And that brings us to our first major takeaway for others: Water use matters. Because agriculture uses most of the state’s water, savings achieved by crop choice, irrigation efficiency and acreage farmed can make a huge difference.

I know these changes aren’t always easy to make, particularly if there’s no market to support them, but that’s no reason not to try.

It also likely strengthens the case for Mohave County to become an irrigation non-expansion area (INA), as city and county officials have repeatedly asked and will lobby for again during this legislative session. Remember: the USGS outlook is rosier mostly because it assumes farmed acres will not expand or markedly change what they grow over time.

And, to be clear, the USGS model is not all roses for the basin. It predicts that some shallower areas near the mountains dividing the two sub-basins could begin to go dry as early as 2040, and the two sub-basins could become hydrologically disconnected by 2080.

That’s a problem, even if water use doesn’t grow, because it could markedly change how each sub-basin is managed when groundwater can no longer flow between them. Agricultural interests in the Hualapai sub-basin would no longer be able to reap the benefits of municipal recharge in the Mohave sub-basin, for example.

And even if the USGS predicts higher groundwater levels for longer than we thought, its model still shows that both municipal and agricultural uses are pumping more groundwater than they replenish.

So, even if lower projected water use may have bought them time, they still have a problem to solve (and one that could easily become more dire if any conditions in the model change).

Some might presume the implication for Mohave County and others is to relax. But leaders like Rep. Regina Cobb and retiring county Supervisor Gary Watson are right that the study underlines the need to keep working for policy changes and find funding for projects that will help make the county’s water supply more sustainable.

A spot of good news does not let them off the hook for that.

That leads me to the final takeaway for other rural counties with groundwater issues: Somehow, some way, we need to find the funding to create similarly detailed, updatable groundwater models for them, too.

Mohave County dug deep to find the money, and I get that not all counties – particularly cash-strapped La Paz County – have that luxury. But every community deserves a similarly robust, updatable tool to make critical decisions about its future.