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

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Metropolitan Water Supply Investigation

MWSI Results

The Willows Water District and Denver Water, in conjunction with the U.S. Bureau of
Reclamation, have also conducting pilot scale groundwater recharge studies as part of the
Bureau's High Plains Aquifer Recharge Demonstration Project.

Coniunctive Use With Borrowina and Groundwater Recharae

A more comprehensive conjunctive use plan would require the coordinated operation of
surface water and groundwater systems. Under this arrangement, groundwater supplies
would serve as a drought-year supply for both groundwater and surface water systems.
This would allow groundwater users to be served exclusively by surface water - both
from runoff and from water released from surface reservoirs - during wet and average
years. This would create greater draw-downs of surface reservoirs, allowing them to
capture a greater amount of surface water during runoff periods. Under this mode of
operation, water users relying on surface reservoirs could be exposed to additional risk of
not refilling reservoirs in the event of drought. But this risk would be alleviated by the
ability to supplement the surface water system with groundwater during droughts, thereby
"paying back" the water "borrowed" from surface reservoirs. This type of a conjunctive
use arrangement would require considerable cooperation among participating
groundwater and surface water providers.

The surface water captured under a conjunctive use plan could be used to offset existing
groundwater use and extend the life of existing non-tributary groundwater-dependent
supplies. This would also stabilize future pumping costs, which would othetwise
increase as aquifer levels decline. To the degree that a conjunctive use plan is designed
for this purpose, the potential for "new yield" from that conjunctive use plan decreases,
At the same time however, the long term operations, maintenance and replacement costs
would be lower because of less aquifer decline.

Alternatively, the surface water captured under a conjunctive use plan could be
temporarily stored in aquifers and used to produce additional firm yield. Under this latter
approach, conjunctive use is similar to new reservoir construction except that the
additional storage space is achieved by using the storage capacity of aquifers.

A conjunctive use plan could also be designed to address a combination of both purposes:
offsetting existing groundwater uses and generating new yield.

3.2.1.3. Surface Water Availability

Information was gathered on surface water supplies potentially available for conjunctive
use. Based on T AC guidance, potential surface water supplies that met the following
criteria were assumed:

I. They would be divertible by metro Denver area providers under new or existing
water rights.

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