PUB00053

• Year: 1999
• Title: Metropolitian Water Supply Investigation Final Report
• Author: Hydrosphere Resource Consultants
• Description: Metropolitian Water Supply Investigation Final Report
• Publications - Doc Type: Water Resource Studies

Metropolitan Water Supply Investigation

MWSI Results

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3.2.1.2. Conceptual Description of Conjunctive Use

Conjunctive use as a water management strategy can take several forms. Common to all
forms is the use of groundwater and the storage function of aquifers to supplement and/or
regulate surface supplies. Both alluvial and Denver Basin groundwater systems can be
employed in a conjunctive use strategy. The following descriptions pertain to a
conjunctive use strategy applied to the metro Denver region and the Denver Basin aquifer
system, since this is the region's largest groundwater source.

When there are divertible surface water supplies legally available, a conjunctive use
system would capture and utilize these surface supplies, and would utilize Denver Basin
groundwater to meet the demands at times when surface supplies are not available. By
jointly using surface water and groundwater supplies and systems, opportunities exist to
develop new yield and to prolong the life of groundwater resources. While the concept of
conjunctive use is interesting, there are issues and concerns associated with conjunctive
use that are discussed at the end of this section.

Direct Use of Surface Water. Groundwater Back-Uo

Under the simplest form of a conjunctive use plan, groundwater providers would use
surface flows when legally available during runoff periods and would rely on wells
during periods when surface flows were unavailable. This arrangement would extend the
physical life of aquifers,

This arrangement historically occurred between Denver Water and the Willows Water
District. Since the mid-1980's, Denver supplied surface water to Willows on a temporary
and interruptible basis. Willows used the water supplied by Denver to meet its demands
in those years, thereby reducing its reliance on its deep wells, which were its principal
source of supply. (Denver and Willows have subsequently entered into an agreement
under which Denver eventually will supply all ofthe potable water in Willows' service
area.)

Direct Use of Surface Water With Groundwater Recharae

Groundwater recharge could be added to this basic conjunctive use arrangement. In this
case, available surface water in excess of that needed to meet demands would be treated
to potable standards and injected into aquifers via wells. This would increase the capture
of surface flows and would replenish aquifers. Recharged water could then be pumped
and used at a later time.

Prepared for the Colorado Water Conservation Board, Colorado Department of Natural Resources by
Hydrosphere Resource Consultants, 1002 Walnut Street, Suite 200, Boulder, CO 80302

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The Centennial Water and Sanitation District is already practicing this form of
conjunctive use. Centennial uses available surface water from its surface water rights, its
augmentation plan, its surface water contract interests, and from spot sales of water from
Denver in order to minimize pumping of Denver Basin wells. In 1996, an above average
year, Centennial met over 90% of its municipal demand from surface supplies and
recharged approximately 500 acre-feet of surface water into its Denver Basin wells.

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