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Dave Grossman's avatar

On Wednesday, a series of cells moved through the Grand Valley of western Colorado with unbelievable fury. It went from the dog sunbathing in the front yard to a whiteout of hail and sheets of rain in about four minutes. My weather gauge showed a peak rate of .94”/hr, but I doubt it had any chance to accurately record the volume and ferocity of the storm. It hit for just over 8 minutes and then cleared with sun out another five minutes later. In that short and violent period, my kitchen window was completely sluiced as if it was a windshield. And my kitchen window is under a 20’ back patio. Every depression had multiple inches of puddles. Trees stripped of leaves. I was worried the roof was going to come off.

This is our new reality. The feedback loop of our emissions are beginning to exert their influence. We are over the tipping point.

Jason's avatar

Your guess, as usual, is very correct. Yes, the Mormon owned Tributary development will be on the Aurora water system.

And thanks to your excellent piece today, I fell down a rabbit hole on Aurora's water situation, mostly because of how much building is happening east of the city near DIA, plus I live in Boulder, so Front Range water is of great interest to me.

Right now Aurora is in a Stage 1 drought and asking people to cut outdoor watering by 20%. The reservoirs are sitting around half full, something like 73,000 to 77,000 acre-feet out of roughly 156,000 acre-feet of capacity. Aurora's own line is that it could take several wet winters to get storage back to where they want it.

Meanwhile the city keeps approving growth to the east. Tributary by itself is about 960 acres and eventually around 12,000 residents. Then you've got Aurora Highlands, Painted Prairie, Windler, the Aerotropolis development around the airport, and more land beyond that already lined up.

Their long-range water plan puts numbers on it. Demand goes from about 63,300 acre-feet in 2025 to as much as 132,400 by 2070. Basically double.

To be fair, Aurora's water system is genuinely impressive. Supply comes out of three basins, roughly 50% South Platte, 25% Colorado River, 25% Arkansas, and they operate 12 reservoirs. Prairie Waters lets them pull legally reusable water back out downstream and run it again, which is why indoor use barely dents the supply compared to watering a lawn. It's also why they've gotten so strict about turf in new subdivisions.

Reuse still doesn't make water, though. Neither does storage. Whatever actually gets consumed has to be replaced, so Aurora keeps buying rights, keeps expanding reuse, and has projects like Wild Horse Reservoir in the pipeline.

Which is where it gets interesting to me. Aurora isn't running out of water. Not close. They've built one of the better municipal systems in the state. But they're under drought restrictions with half-empty reservoirs while signing off on an enormous amount of new rooftops, on the strength of a plan that assumes they can roughly double their water capacity.

Can Aurora serve Tributary? Yes. Easily. The harder question is whether they can double the whole system over the next few decades while the supplies underneath it, Colorado River included (a quarter of their surface water), keep getting shakier.

Thanks as always for the excellent writing Jonathan.

- Jason

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