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Spring runoff is vital for Denver Water’s supply

spring runoff
Denver Water experts closely monitor weather conditions and streamflow during the spring. Photo credit: Denver Water.

Deep drifts of snow in the winter don’t automatically mean full reservoirs come summer.

That’s especially true after last summer, one of the hottest and driest in Denver Water history. Denver Water experts closely monitor weather conditions and how much melting snow is flowing down mountain creeks.

This information will help determine whether additional water restrictions, beyond the regular summer watering rules, may be necessary in coming months.

“I look at snowpack like your gross paycheck,” said Nathan Elder, Denver Water’s manager of water supply.

“But then you have things taken out of it, like taxes, Social Security and health care. What’s left is what actually goes into your bank account. For water, that’s the runoff, that’s the water that actually goes into the reservoirs.”

The spring runoff typically starts at the end of April and peaks weeks later in the middle of June.

Several factors can eat away at a healthy winter snowpack, reducing the amount of water that ultimately ends up in reservoirs. Among them:

  • Wind: Winds can pick up the snow and move it around. And a warm, Chinook wind can melt the snow away.
  • Evaporation: Water is always moving into the air, or evaporating. The amount of snow that disappears through evaporation increases as temperatures rise.
  • Soil moisture: Mother Nature gets first dibs on the water in the snow, with the soil soaking up moisture like a sponge.

Only when the soil is saturated does the remaining water run into streams and reservoirs.

The timing of the annual spring runoff also is important. A longer, later runoff that stretches through late spring into summer delays the need for Denver Water to rely on its network of storage reservoirs to meet the needs of its customers.