BOARD00244

• Board Meeting Date: 7/23/2002
• Description: CF Section - Statewide Water Supply Investigation - Review Plan of Study
• Board Meetings - Doc Type: Memo

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retirement of these toilets, facilitated by rebate programs administered by water
providers, would save millions of gallons per day as have successful programs in Tampa,
Florida, Austin, Texas, New York City and Los Angeles.

The typical residential washing machine uses 50 gallons per load. Models exist that use
between 16-27 gallons per load.17 These machines cost more than conventional washers,
but they save their users water and electricity. Rebates by water providers have been
useful in encouraging customers to purchase these more efficient machines.

Plumbing fixtures can save water, too. In Seattle, Washington, over 330,000 low flow
showerheads were distributed to residential customers door-to-door, saving close to 6
million gallons of water per day. IS .

Rebates by water providers to customers to buy down the incremental cost of new
appliances are the most time-tested and successful way of achieving the savings available
in indoor uses. Low-flow showerheads are so inexpensive, they usually are simply given
away, the savings to the water provider covering the costs in little time.

Many of the conservation measures discussed above are relatively inexpensive compared
with the construction of new large dams, especially those that depend on the importation
of water from the West Slope.

Other water-use efficiency measures:

Water conservation is but one way of making existing supplies go further. Several other
techniques exist. One of them is reducing the amount of unaccounted-for water (VA W),
a/k/a fixing supply system leaks. Denver Water is a regional leader, reducing UA W to
6% in 2001, yet many of our water providers lag behind this benchmark.

Another such technique is re-use of water. Only about 50% ofthe water diverted and
delivered for municipal uses is actually consumed in its initial application. The
remainder returns to the stream in the form of wastewater, return flows from irrigation of
lawns, parks and golf courses, and subsurface losses from the treated water distribution
system. Some of this water can be reused. For example, "effluent management" utilizes
municipal return flows to increase municipal water supplies. There are two ways to
accomplish this goal: return flows can be treated and reused for potable and non-potable
purposes; and/or return flows can be reused under substitution or exchange arrangements.

Coniunctive use of surface and groundwater, another technique, has the greatest potential
in areas where some component of supply is from underground aquifers, as is the case in
. the south Denver metro area. Conjunctive use of surface and groundwater means that in
. wet years, cities rely on surface water and use "surplus" water to recharge aquifers, and
in dry years, cities rely more heavily on groundwater. Overall, the goal is to stabilize
ground water tables and have emergency supplies available in case of prolonged drought.

17 Amy Vickers, "Conservation Handbook" at 145.
18 "Regional Water Conservation Accomplishments 1990-1998," Seattle Public Utilities and Purveyor
Partners.

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