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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A number ofPront Range water providers use inverted rate structures. However, none
may serve its purpose as well as that of Irvine Ranch in California. The Irvine Ranch
Water District (IRWD) sets a base allocation for each property based on historic use,
landscape area, number of residents, evapo-transpiration (ET) rates, crop coefficients and
irrigation efficiency. For customers who exceed their base allocation by 50%, rates are
doubled; by 50-100%, rates are quadrupled; by more than 100% rates are eight times
higher.l! There are rewards as well as penalties. If a customer manages to use less than
40% of the base allocation, a 25% discount is awarded. The IRWD has found their rate
structure to be "very defensible" and a means to nurture positive working relationships
with their customers. 12 Perhaps most importantly, this rate structure reduced residential
water use bv 19% during its first two vears!!3

Outdoor uses:

Outdoor water use accounts for about 54% of total residential water use in the Denver
area, most of which goes toward turfirrigation.14 Conserving water outdoors requires
that we plant smart and water smart.

Xeriscaping offers a much lower water-using alternative to bluegrass lawns. Xeriscape
incorporates seven principles to promote quality landscapes, water conservation, and
environmental protection: (I) planning and design; (2) soil analysis; (3) appropriate plant
selection; (4) practical turf areas; (5) efficient irrigation; (6) use of mulches (to retain soil
moisture); and '(7) appropriate maintenance. Skeptics may worry that xeriscapes are just
dull and dry, but well-designed xeriscapes are lush and beautiful, incorporating the native
textures and colors of Colorado's grasses, evergreens, ground covers and flowers.

Some local water utilities, like the City of Boulder and City of Aurora, offer incentives
for residents who replace turf with Xeriscape. However, we could go much further.
Regional leaders, like El Paso, Texas, offer $1.00 per square foot of grass replaced with
water-efficient landscapes. El Paso's program led to replacing almost 1 million square
feet of grass and saved over 20 gallons per square foot removed each watering season. 15

Most of us, even when we avoid bluegrass, apply far more water than grass and plants
actually need. And most of us use sprinklers, sometimes in the middle of the day, losing
a substantial quantity ofthe water applied to evaporation. We can do better.

A promising technique is drip irrigation, which usefully applies 30%-50% less water than
sprinkler irrigation and still meets the requirements of most plants. The City of Boulder
offers modest financial encourage to residential water users through a rebate on the cost
of these systems. Many providers offer no such help.

II Arlene Wong, "promoting Conservation with Irvine ranch Water District's Ascending Block Rate
Structure," in Sustainable Use of Water: California Success Stories (Pacific Institute, I 999) at 27-35,
12 Id. at 31.
"Id. at 34,
14 Denver Water Conservation Master Plan, 1997 at 4.
IS Ansi Padilla, E1 Paso Water Conservation Program (April 22, 2002) at 8.

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