Land & Water
Land & Water by Terry Stokka


The Denver Basin and individual wells

By Terry Stokka

     I have written a few articles in the past about water. Those articles have been about water use, the Colorado River and other water related topics. In this article I would like to focus on our own Denver Basin under us and our individual wells. I will present it in bullet form for easier reading.

Water is a very precious and limited resource in Colorado

  •       Black Forest gets an average of 18 inches of precipitation per year — 88 inches of  snow.
  •       Colorado Springs gets 15 inches of precipitation — 35 inches of snow.

The Denver Basin is a giant bowl comprised of four bowls within it.

  • The total bowl stretches from Greeley to the south side of Colorado Springs.
  • The basin extends from the front range out to Limon.
  • The top aquifer, the Dawson, is the smallest; it extends from south Denver to Woodmen Road.
  • Virtually all of our private wells are in the Dawson aquifer.
  • The bowls in the basin are four separate aquifers of water.
  • The aquifers are the Dawson (top,) Denver, Arapahoe and Laramie-Fox Hills (bottom).

Garden of the Gods and Red Rock Open Space are edges of the bowls sticking up out of the ground.

  • Red Rocks in Denver and Flatirons in Boulder are western edges of the bowls.

State water officials believe the four aquifers are sealed from each other; however, no one knows for sure how much the aquifers are sealed from each other Tests from an Arapahoe well affected the Denver and Dawson aquifer above it.

  • Drilling logs do not show a clear, impermeable boundary between aquifers.
  • Denver aquifer is considered to be a “leaky” aquifer to Dawson above and Arapahoe below.
  • Water models constructed by the state and private companies vary in their conclusions.
  • If these bowls are being recharged at all, it is a slow process over generations of time.
  • Majority of the recharge is probably occurring along the edges along the front range.
  • Only a little over half of the Denver Basin water can be economically removed.
  • Through continuous, long-term use, a well becomes less and less efficient.
  • After several years, it is not economical to pump because of decreasing output.

A well-driller with 30 years of experience says the geology of the Denver Basin is not homogeneous

  • The boundary between aquifers is not solid nor consistent.
  • The basin has interlocking and overlapping layers of sand, gravel, sandstone and claystone.
  • Wells 1/4 mile apart can produce widely varying amounts of water.
  • Wells only 200 feet apart can have widely different static levels, which is the distance from   
  • ground level to the water in the well.
  • Having a water allocation or water right is no guarantee of actual amount of water.
  • “Paper water does not equate to wet water.”

Water use in the Denver Basin is 62% agriculture, 20% municipal and 12% domestic (private wells).

For residential households in the Black Forest, the State of Colorado considers water use as follows:

  • An acre foot of water (325,851 gallons) is 1 acre (a football field minus 10 yards); 1 foot deep in water.
  • The average household uses 0.35 acre-feet of water per year. This is 313 gallons per day.
  • If a household has animals or landscaping, the water use goes up to about 0.5 acre-feet per year.
  • 90% of the water used in a household is returned into the ground via the septic system.
  • Just 10% is actually consumed or evaporated into the air.
  • 15% of the water used for watering gardens and lawns is returned into the ground.
  • 85% of irrigation water is evaporated into the air and not soaked into the ground.
  • 100% of the water used for animal watering is consumed and none is returned into the ground.

I hope this summary will give you an education into our Denver Basin and individual wells. I have about two more pages of this type of information. This could turn into a three-part series. 

Standby for more about water and the Denver Basin.

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