BEDROCK AQUIFERS AND POPULATION GROWTH IN DENVER BASIN, COLORADO

The Denver Basin bedrock aquifer system consists of Tertiary and Cretaceous age sedimentary rocks known as the Dawson, Denver, Arapahoe and Laramie-Fox Hills aquifers. The number of bedrock wells has increased from 12,000 in 1985 to 33,700 in 2001 and the withdrawal of groundwater has caused water level declines of over 75 meters. Water level declines during the past 10 years have ranged from 3 to 12 meters per year. The groundwater supplies were once thought to be sufficient for 100 years but there is concern that their supplies may be depleted in 10 to 15 years in areas on the west side of the basin.

Groundwater is being mined from the aquifer system because the discharge by wells exceeds the rate of recharge. Increased groundwater withdrawal will cause water level declines, increased costs to pump groundwater, and reduced well yield. In the Denver basin hydrologists have some capability to monitor declines in water levels for the Arapaho Aquifer, but generally have a limited ability to monitor water use. More accurate data are needed to predict the future groundwater sustainability for the area which will result from increased water use.

Groundwater may limit growth in the Denver Basin over the next 20 years. The life of the Araahpoe aquifer can be extended with imported surface water, artificial recharge, water reuse, restrictions on lawn watering, well permit restrictions and conservation measures.