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• Board Meeting Date: 7/11/2007
• Description: IWMD Section - Colorado's Future Water Supply Needs - Update on Consumptive and Non-Consumptive Workgroups
• Board Meetings - Doc Type: Memo

IV, Opportunities to Improve Agricultural Efficiency for Water Supply

Limited progress was made on agricultural water efficiency by the SWSI Phase 2 Conservation and Efficiency TRT and this
remains a significant challenge, Based on initial work, there appears to be some opportunities to achieve additional
efficiencies in agricultural water use However, since agricultural return flows are used by downstream water users, at a
watershed level there are significant limitations in the overall net potential savings that can be realized, Nevertheless, since
agricultural water use accounts for over 85 percent of total water use in the state, follow-up efforts should include this group
of water users CWCB and Colorado State University are working with the agricultural community to further examine these
issues and opportunities,

V. Alternative Agricultural Water Transfer Methods for Water Supply

SWSI Phase 2 provided an extensive look at all alternatives to a traditional transfer and concluded that fallowing has the
most potential statewide, and may require state assistance, Interruptible supply strategies will also be assessed. There may
be a role for the state, through the CWCB for example, to "level the playing field" through the use of incentives to encourage
M&I providers and users to use alternatives to traditional agricultural transfers in order to foster the maximum utilization of
the state's waters and to ensure that other non-market values (open space, wildlife habitat) are retained.

VI. Assessing the Effects of Climate Variability on Colorado's Consumptive Use Needs

Global warming is expected to alter the pattern of water supply and use in Colorado and should be factored into any long-
range planning Global warming-based changes to supply availability can be examined by comparing projected changes in
streamflow to current hydrographs at locations throughout the State, and estimating evaporative loss to reservoirs, The
change in consumptive water demands in Colorado will be evaluated using the CWCB's consumptive use model StateCU,

VII. Non-tributary Groundwater and Water Use Sustainability

Increasing demand for Colorado's limited water supplies suggests the need to examination of how our water resources can
be used more efficiently, One method to maximize beneficial use is to use surface and groundwater resources in a more
fully integrated manner through conjunctive use management This is a proven strategy that recharges aquifers during wet
periods and relies on them during dry periods, Studies conducted by the CWCB and Colorado Geological Survey have
shown that considerable storage exists in both alluvial and bedrock aquifers throughout the State,

VIII. Recalculate the Gap

The current Gap identified In SWSI is 118,200 AF based on the ability of the IPPs to address new demands An update to
the IPPs and the new demand projections out to 2050 will be used to recalculate for each basin, Additional considerations of
climate variability and groundwater sustainability will also be considered in recalculating the Gap, Climate variability will play
a role in determining the revised Gap and is described in detail below In the South Metro area it is also anticipated that
aquifer production will decline by 40 to 80 percent by the year 2050, and that municipal well production will decline,
Conjunctive use of available surface water supplies can reduce these costs and decrease the annual demand on the
aquifers by 50 percent

PRELIMINARY DRAFT

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