BOARD01380

• Board Meeting Date: 11/23/1998
• Description: CWCB Director's Report
• Board Meetings - Doc Type: Memo

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distribution infrastructure serving the metropolitan area would be necessary, but such
improvements would not entail major new on-stream reservoirs,

.

While each water supply category evaluated in the MWSI appears to present significant,
technically feasible cooperative opportunities, each also raises several issues that present
serious obstacles to implementation without considerable additional work.

The table below summarizes the MWSI's findings,

Supply or Yield Potential
up to acre- eet
of yield under example
project analyzed

Actions Items/Unresolved Issues
out atte an ue Iver stream ep etlons
changes in water rights
feasibility of long,term, large scale recharge
IGA's among participants
Ig costs
public acceptance of potable reuse
effects of exchanges on water quality
effects on instream flows
wou require major inS u lona c anges
impacts to agricultural communities
geographic/cost considerations

uent

t er ystem
Integration
Opportunities

c anges In water ng ts
IGA's among participants
Federal action (Chatfield storage reallocation)

.

COOPERATIVE WATER SUPPLY OPPORTUNITIES

Coniunctive Use would involve the linkage of groundwater systems currently serving
communities in parts of Douglas and Arapahoe counties with the Denver Water system.
Water available from the Denver system in average and wet years could be used to meet
demands and for recharge of Denver Basin aquifers. Groundwater sources would be used
to meet demands not fully satisfied by surface water sources and during periods of
drought. For the example project analyzed, conjunctive use arrangements could yield up
to 60,000 acre-feet per year to meet new demands or reduce existing groundwater
pumping from the Denver Basin aquifers.

Conjunctive use presents a promising solution to continued dependence upon non-
renewable groundwater resources by the growing communities in the South metro sub-
region, Conjunctive use also raises several unresolved questions. To the extent that a
conjunctive use project would rely on additional transmountain diversions from existing
facilities and water rights, this would likely engender concerns among West Slope
residents, However, the operational flexibility inherent in a conjunctive use project could
allow for mitigation of many impacts while still generating significant yield, Other issues
and uncertainties associated with conjunctive use include changes in water rights, the
feasibility of large-scale recharge over the long term, and the challenges associated with

.

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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