PUB00102

• Year: 1998
• Title: Denver Basin and South Platte River Basin Technical Study
• CWCB Section: Water Conservation & Drought Planning
• Author: Simpson/Lile
• Description: Results of study to investigate Denver Basin groundwater management and South Platte River Basin issues
• Publications - Doc Type: Brochure

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The overall view of the Denver Basin Aquifers also reveals a complex combination of
water use and resource protection. The Denver iBasin Aquifer system consists of the
Dawson (upper and lower), Denver, Arapahoe (~pper and lower), and Laramie-Fox
Hills aquifers. The aquifers cover an area of ab~ut 6,700 square miles extending from
Colorado Springs on the south to Greeley on the north, and from the foothills on the
west to Limon on the east (Figure 1 and 2). '

The Aquifer system contains approximately 300 million ac-tt of drainable storage. To
put this quantity of water in perspective, this amounts to a reservoir 15 times greater
than the active storage of Lake Powell (20 million ac-ft) , and 400 times greater than the
active storage of Blue Mesa Reservoir (750,000 sc.tt). The estimated total pumping of
groundwater from the Denver Basin Aquifers in 11996 was 56,000 ac-ft. This is less
than 2% (60,000 ac-ft) of the 1 % (3,000,000 ac-ft) annual allowable pumping quantity
under the 100 year aquifer life administration criteria provisions of Senate Bill 85-5.

Eventhough some localized well pumping drawdowns and loss of hydrostatic pressure
are occurring, the overall Denver Basin aquifer life at this level of production (56,000
af/yr) may exceed 1000 years. Simplified projections of well development and
population growth to the year 2100 result in groundwater production estimates of about
300,000 ac-tt per year which is about 10% of theiannual allowable pumping from the
Denver Basin aquifers under the 100 year aquifer life assumption. Depending on
unknown future conditions, this amount could be !significantly different.

The impacts to South Platte River flows and the potential injury to senior water rights
due to depletions from ground water pumping arEj not currently evident due to the net
increased flow in the South Platte from Denver B~sin aquifer return flows and due to
the delayed impacts of pumping. Therefore, wat~r policy decisions related to the long-
term use of this nonrenewable resource and the Ijl'lanagement of the South Platte River
are not immediately critical. However, these water policy issues must be addressed
over the next few years through the development, and use of advanced computer
modeling, improved data bases and a more thorough understanding of all the potential
causes of injury to senior water rights on the South Platte prior to changing existing
statutes.

II. Public Water Policy Issues

This study has raised a number of water policy issues that must be addressed
through additional study and public meetings, and by the legislature acting in its
role as "decision maker" in public water policy.

The water needs of the Denver metropolilim area and South Platte River basin
are increasing as ,a result of population! growth. Water for this increasing
population will come from a combination of!six sources: 1) Water conservation 2)
Water reuse 3) Trans-basin imports 4) Conversion of in-basin agricultural water