S5_11-15-04

• Basin: Statewide
• Title: SWSI Phase 1 Report - Section 5 Projected Water Use
• Date: 11/15/2004
• Author: CWCB
• SWSI - Doc Type: Final Report

Section 5
Projected Water Use
SWSI as options toward addressing future water needs
in each basin, as part of alternatives developed by the
SWSI team in conjunction with Basin Roundtable
participants.
The National Energy Policy Act of 1992 set
manufacturing standards for improved water efficiency
for toilets, urinals, showerheads, and faucets. These
standards became effective in 1994. The standards for
commercial fixtures became effective in 1997. These
standards affect the types of water-using fixtures
available for new construction as well as remodeled or
renovated facilities, and result in improved indoor water
use efficiency. In addition, some municipalities have
ordinances that limit turf or irrigated areas, which reduce
outdoor water use.
Typically, estimates of Level 1 conservation savings for a
given water utility service area, or other planning area,
are a function of characteristics of the service area such
as the percent of water efficient fixtures present at some
base period in time and subsequent new construction
and remodeling.
The allocation of total water use among various uses
may be seasonal. For example, irrigation is expected to
be a larger component of total water use in summer
months than in winter months. Locations affected by
landscaping ordinances may have a greater impact from
Level 1 conservation in the summer months, while
locations without landscaping ordinances may find the
impact of Level 1 conservation to be more noticeable in
winter months.
The estimation of conservation savings requires an initial
baseline forecast of water demand without conservation.
The baseline water demand forecast is driven by
projections of future demographic growth for the study
area and does not account for the effects of future water
conservation. Impacts of conservation savings can then
be determined from the baseline water demand forecast.
Five studies of estimated conservation savings that
followed similar methodologies for estimating
conservation savings were reviewed in estimating
Level 1 conservation savings for SWSI. The average
expected percent reduction in baseline water demand
from Level 1 conservation savings based on these
studies were identified as shown in Table 5-3.
~~
Table 5-3 Antici ated Lev~el 1 Conse~rvation Savings b Yy ear
~~~ ~~ ~o ~~
Expected Savings 2.5% 5.0% 7.0% 8.5%
Increase above 0% 2.5% 4.5% 6.0%
2000
Year 2000 water use data were used to develop the
SWSI baseline demand forecast. Thus, the SWSI
baseline demand forecast is reflective of water
conservation (both passive and active) in effect in the
year 2000. Conservation adjustments to the SWSI
baseline demand forecast should reflect future impacts of
conservation.
The M&I baseline water demand for each county was
adjusted by these percent savings factors to account for
the impact of Level 1 conservation savings. The resulting
estimate is used as the lowest conservation scenario
(Level 1).
5.1.1.6 Estimate of M&I CU Rates
Water use can be considered both in terms of gross
water needs - the total amount of water delivered to a
user - and in CU. Both are important considerations in
water planning. The difference between gross and CU is
the amount that is realized as return flows (i.e., through
wastewater treatment plants and lawn watering). CU is
generally higher in arid and semi-arid regions such as
Colorado, where more water is used for irrigation and
lost to evapotranspiration.
The Colorado River Return Reconnaissance Study
(Boyle 2003) cites the source of its CU rates as the
Colorado River DSS Consumptive Uses and Losses
Application Report (1999), which details the application
of the State of Colorado's CU model (StateCU) (for the
Colorado River tributaries and the Rio Grande Basin).
This document states that for municipal use the CU
ratios for urban (36 percent), rural (36 percent),
commercial (35 percent), and public (35 percent) use
were obtained from the BOR. Note that the BOR urban
and rural CU of 36 percent is used in the BOR Gunnison
Basin Study (2001).
As part of the Cooperative Agreement regarding
endangered species in the Central Platte River in
Nebraska, Colorado developed a method for estimating
current and future water use. Through this process, a CU
rate of 35 percent for M&I uses in the Platte Basin was
developed (DNR 1998). It was also noted that while this
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