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
In these instances, wastewater returns and return
flows from lawn irrigation have been quantified and
may be used to maintain historical return flows such
that historical CU is not increased. Conservation that
results in reduced volumes of wastewater or lawn
return flows can require M&I users to acquire
additional water supplies to maintain these historical
returns.
^ Augmentation plans can be developed that account
for wastewater and lawn return flows, and only require
that the M&I CU be replaced. As a result,
conservation would not result in an increase in supply
unless the M&I CU is reduced, such as through the
reduction in total irrigated areas of lawn. The
assumed CU is usually decreed in an augmentation
plan and as a result, any attempt to use conserved
water would require a re-opening of the augmentation
decree to re-quantify CU. This action would likely be
costly and could present a high level of risk to the
water provider.
^ M&I landscape irrigation return flows, in addition to
satisfying downstream rights, also creates delayed
return flows than can have instream and riparian
environmental benefits, and maintains aquifers for
domestic and irrigation wells.
8.2.1.3 Agricultural Conservation (Efficiency
Improvements)
Agricultural conservation or agricultural efficiency
implementation is a means to create new water supply
that must be carefully evaluated since Colorado water
law and interstate compacts may limit or preclude the
use of this option to increase supply. This option involves
increasing the efficiency of water used for irrigation, so
that more of the water that is diverted from streams and
rivers or pumped from groundwater meets the direct CU
needs for agricultural crops. Typical agricultural
efficiency measures include canal lining or the
conversion of irrigation practices and technology from
flood irrigation to gated pipe or the installation of
sprinklers or drip irrigation systems. These measures are
designed to reduce the delivery losses that occur as
water is diverted from a stream or as groundwater is
pumped and delivered to the farm or ranch or as it is
applied to the crops.
Table 8-3 shows the range of expected application
efficiencies for different types of irrigation practices and
the approximate costs to install these irrigation delivery
systems.
~~
Table 8-3 Estimated Efficiencies and Costs for Irrigation
Methods

Flood ,u.-

30-50% _-
&:
-
Furrow 40-60% $37 $30
Gated Pi e -60% $178 $51
Center Pivot Circle -85% $433 $64
Center Pivot with Corner -85% $568 $80
The benefits of agricultural efficiency measures include
^ Increased ability to deliver water to the crops can
stretch existing supplies. This benefit would apply to
water short irrigators that would benefit if additional
water could be delivered to their crops. If the irrigator
that has water short crops typically experienced
50 percent losses, reducing those losses will result in
an increased delivery to the water short crops and a
resulting increase in crop CU.
^ Agricultural efficiency may reduce non-crop CU.
Some of the CUs and losses may be due to tailwater
from irrigation ponding at the end of fields and
evaporating, rather than returning as surface or
groundwater return flows.
^ There may be potential water quality benefits. Canal
seepage and/or flood or furrow irrigation may result in
the leaching of minerals from the soils that result in
impacts to the water quality of the return flows. Lining
canals or the installing sprinklers may reduce the
leaching of these minerals. This must be examined on
a site-specific basis, as some irrigated fields may
require periodic flushing of salts and minerals that
accumulate in the soils in order to remain productive.
The benefits of these improvements accrue to many,
and programs like the Colorado River Salinity Control
Program exist to encourage these types of
improvements.
^ No new diversions are required from rivers or
streams.
^ Permits are not required for implementation.
There are a number of potential issues and conflicts that
must be evaluated for the potential implementation of
agricultural efficiency measures.
^ Historical agricultural return flows are a vital part of
the flows in all basins and downstream surface water
diverters and downstream states have relied on these
return flows.
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