28

• Board Meeting Date: 3/18/2008
• Description: IWMD Section - Presentation of Agricultural Water Conservation Paper
• Board Meetings - Doc Type: Memo

Executive Summary
transferable is an irrigator's historic consumptive use, not the amount of water diverted.
hlcreasing irrigation efficiency is likely to reduce losses from deep percolation and
runoff, but it may or may not materially affect the amount of water consumed by the
plant. Much of the water lost to these inefficiencies will return to the river or
groundwater system for use by downstream water diverters. The reliance upon
irrigation return flow s is a common occurrence in Colorado and downstream water
rights holders that relied upon historical return flows are entitled to protection from
injury that could occur when a water right is changed. For this reason, the law and
customs in Colorado are clear that water made available from reduced diversions is not
available to the original appropriator for irrigation of additional acreage or transfer to
other uses. For agricultural water conservation measures to be successful, these aspects
of water in Colorado must be considered.
Reductions in crop consumptive use (conserved consumptive use water) only occur
when: 1) Irrigated acres are decreased, 2) crop selection is changed from a summer crop
to a cool season crop, 3) crop selection is changed to one with a shorter growing season,
4) deficit irrigation is practiced, applying some amount less than full or historical
evapotranspiration over the growing season, or 5) evaporative losses from the field
surface are reduced as a result of conservation tillage, mulching, and or drip irrigation. It
is important to recognize that reducing agricultural water consumptive use will limit
crop yields and may increase producer exposure to risks such as irrigation system
failure, pests or drought. Implementing water conservation measures usually results in
increased equipment, labor, and management costs that must be borne either by the
irrigator or by those who benefit from the conserved water.
Increased and enhanced use of irrigation water conservation measures may be beneficial
in certain areas of Colorado if the basin scale impacts are evaluated as part of the
adoption process. Increased agricultural water conservation could potentially result in a
voluntary reduction in the diversion of water to the farm, creating benefits such as
improved water quality, allowing more water to remain in the streams, reduced
waterlogging of soils, and reducing energy costs for pumping, but may not result in
water that can be legally transferred to other uses. If the use of water conservation
measures can improve water supply availability without causing injury to downstream
users or the environment, then the result may be improved water supplies for
agriculture and other uses.
The Colorado Ag Water Alliance believes that water conservation is only one
component n1 meeting Colorado's future water needs. Better use of existing surface and
groundwater storage resources and the development of new storage to meet future
demands and for drought years will be required to meet both existing agricultural
shortages and future MCI demands. In order for agricultural water conservation to play
a meaningful role in meeting the State's future water needs, a number of legal and
admiiustrative issues must be resolved and sufficient financial incentives offered to
mitigate the increased risk and loss of productive capacity that occur under reduced
water supplies. Furthermore, an in-depth basin-by-basin analysis of agricultural water
conservation will need to be conducted to gauge the opportututies to obtain transferable
water within the constraints of our interstate compacts and priority system.
DRAFT ES-2