SRP has sent enough water downstream to fill Phoenix taps for a year
Salt River Project began slowly releasing water from its Verde River reservoirs in early March to make room for melting snowpack.
But about 300,000 acre-feet of water – roughly what the city of Phoenix delivers to taps each year – has already rushed downstream.
With a lot more to go.
Why is SRP releasing water?
Salt River Project manages reservoirs on the Salt and Verde rivers, delivering water to about 2 million folks in metro Phoenix.
The Salt’s reservoirs can store roughly 2 million acre-feet – enough to submerge the city of Phoenix in about 6 feet of water.
But the Verde’s reservoirs are much smaller, with capacity to store less than 300,000 acre-feet.
SRP often releases water in wet years to take pressure off the dams and free space for additional snowmelt.
Ideally, this would happen slowly and steadily, so cities and farmers have time to capture and put that water to use. SRP started releasing small amounts in early March to try to get ahead of the curve.
But a series of warm storms accelerated runoff – and the amount of water that SRP must release each day.
How much water could spill?
Charlie Ester, SRP’s surface water manager, initially estimated that SRP could spill about 100,000 acre-feet on both rivers by the time heavy snowpack melts.
But already three times that has been released, mostly from Verde reservoirs.
And this season’s snowpack is the deepest in 30 years.
Ester now estimates that 600,000 to 800,000 acre-feet could spill by the end of runoff season, which should continue through at least April.
The good news is we’re going to have full reservoirs.
And the torrent of water should help recharge the aquifer as it rushes downstream, providing a much-needed boost for the groundwater on which many of us will increasingly rely.
The downside is a lot of water is rushing out of metro Phoenix before it can be put to beneficial use.
Shouldn't we do more to capture runoff?
SRP wants to raise Bartlett Dam on the Verde River, primarily to regain storage capacity lost at the upstream Horseshoe Lake, which is slowly filling with sediment.
That project also would add additional storage space on Bartlett Lake, enough to produce up to 115,000 acre-feet of additional water a year for users.
New reservoir proposed:But it wouldn't boost water supplies
Meanwhile, on the Salt River, SRP wants approval to change how it manages Roosevelt Lake, the system’s largest reservoir, so water can occupy a small portion of the lake’s existing flood-control space for up to 120 days.
Doing so would create an additional 105,000 acre-feet of temporary storage space, buying time for a slower release.
Neither of these projects would prevent a spill as large as this year’s could be, but it certainly would lessen its impact.
Why isn't this space available now?
SRP has been working on these ideas for years.
But the reservoirs are ultimately federal projects that must undergo rigorous environmental reviews before any modifications get the green light.
Money from the federal infrastructure act is helping to fund a required feasibility study for the Bartlett Dam extension.
But it’ll be years before that project could provide additional storage space on the Verde River.
Meanwhile, the Roosevelt pilot could win federal approval by the end of this year – albeit too late to capture this spring’s runoff.
What if next winter is dry?
It’s possible. But that doesn’t negate the need for extra storage space.
In fact, climate change makes it even more critical.
Experts believe that precipitation in the Salt and Verde basins could become a case of feast or famine.
If they’re right, we’ll need more space to capture more water in those wet years.
Because heaven knows we’ll need it for the dry ones.
Reach Allhands at email@example.com. On Twitter: @joannaallhands.
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This article originally appeared on Arizona Republic: SRP water releases could fill Phoenix taps for a year