DENVER – We knew the June snowmelt would boost Colorado's thirsty reservoirs, and now we can see just how much: Statewide, the reservoirs went from 59% capacity at the end of May to 76% at the end of June.
That still leaves plenty of room for more water, but the reservoirs are now sitting above average, at 105% of the normal capacity.
At the end of May, statewide reservoir capacity was at 90% of the average.
When June began, Colorado was still seeing extremely high snowpack percentages, when compared to the normal rates. Statewide snowpack was more than 400% of normal, with highs of more than 700% in the San Juan Mountains.
But after a month of warm temperatures – and even despite a late June snowstorm – the snowpack is nearly gone, following the usual melting pattern as summer begins. The result was some minor, isolated flooding and a surge in river streamflows across the state. And the reservoirs have soaked up the moisture.
The Gunnison River, Upper Colorado River and Upper Rio Grande basins all saw significant upticks in reservoir levels. The Gunnison jumped from 60% to 85%; the Upper Colorado from 67% to 92%; and the Upper Rio Grande more than doubled, from 26% to 54%.
"It took a little while for the melt to happen (which was generally a good thing to mitigate any flooding concerns), but now that the melt has nearly completed, the streams and rivers are really flowing, and the reservoirs have started to fill nicely," Russ Schumacher, a climatologist with the Colorado Climate Center in Fort Collins, wrote in an email.
Those increases were reflected in some of the biggest reservoirs in the state:
The Dillon Reservoir is now at 97% capacity, up from 73%. The Blue Mesa Reservoir is now at 84%, up from 54%. Lake Granby is at 91%, up from 64%. The McPhee Reservoir, which was already at 88% capacity, is now full.
Further down the Colorado River, Lake Powell in southern Utah has seen its levels rise slightly, Schumacher said, but it's still below average. The levels there should rise as the uptick in Colorado and Utah rivers travels south. But it could take one more wet year to see Lake Powell return to normal levels, Schumacher said.
The moisture in Colorado has had another benefit: The state is still 100% drought-free. And there's been even more improvement in that area. The Palmer Drought Severity Index in Colorado , which sat at -0.72 in May, jumped into positive territory, at 2.28, indicating normal levels for the first time since the latter half of 2017.