S8_11-15-04

• Basin: Statewide
• Title: SWSI Phase 1 Report - Section 8 Options for Meeting Future Water Needs
• Date: 11/15/2004
• Author: CWCB
• SWSI - Doc Type: Final Report

Section 8
Options for Meeting Future Water Needs
^ These return flows, in addition to satisfying
downstream water rights, also create delayed flows
that can have instream and riparian environmental
benefits and maintain aquifers for domestic and
irrigation wells.
^ Typically, any water that is saved by efficiency
measures such as canal lining or the conversion of
irrigation practices and technology from flooding to
gated pipe, center pivot circle, and center pivot with
corner can only be used on lands for which the
appropriation was originally made. Selling or
delivering "saved" water to other users would
constitute an improper expansion of use.
8.2.2 Agricultural Transfers
Agricultural uses currently account for more than
80 percent of the water diverted and consumed in
Colorado. Many agricultural users hold senior water
rights that can potentially be changed in use to provide a
significant source of M&I water supply. In agricultural
transfers, farm land is usually "dried up" or no longer
irrigated and the water historically used for irrigation of
this land is used for meeting M&I or other needs, such as
dedication to CWCB for instream flow purposes.
1.4
50% irrigationefficiency
Section 4 of this report describes the general background
of agricultural transfers. The total water available under a
change of agricultural water rights typically depends on
the historical CU of the water for agricultural purposes:
this is a measure of the water right for transfer. In
addition, the yield of an agricultural water right may
depend upon the location of the new use of the water.
For example, in general, if the water is to be diverted
through the same ditch system as historically, a transfer
to M&I use may allow diversions of all of the water
previously diverted at the historical farm headgate
though the historic CU cannot be increased. The water
that may be diverted on a transfer of water from an
agricultural use to one out of the basin will be limited to
the historical CU. Meanwhile the historical return flows
must be maintained; storage may be needed to ensure
that other water rights that historically relied on return
flows are protected. After the historical return flows have
been replicated, it is legal for the transferred
"consumable" water to be used and reused to extinction.
A graph illustrating the yield from an agricultural transfer
project, shown in conjunction with the reuse of a portion
of the return flows used for M&I irrigation of landscaping,
is provided in Figure 8-3.
1.2
65% irrigationefficiency
~ ----------------- ------------------------------------------
LL consumptive use transfer (100% efficiency)
? o.s--------------------------------------- ----------------------
~
a
.~
e
w 0.6 ,
06
~
assumes:
0.4 - 35% M&ICU ---------------- I
1.2 AFIAC Ag CU
2.0 average:firm yield ratio
02 ----------------i
0 •
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
percent reuse for irrigation
Figure 8-3
Firm Yield to M&I User from the Dry Up and Transfer of 1 Acre of
Irrigated Agricultural Water Use
J~~a
$~ole'ri~ice Wo~e' $upplY Initia~ive
~~
S:\REPORT\WORD PROCESSING\REPORT\S8 11-9-04.DOC H-7