Irrigation is by far the largest consumptive use of diverted water in the Columbia Basin, so it is not surprising that improved irrigation efficiency is often discussed as an approach to enhance instream flows and improve water quality for fish. The Council’s Fish and Wildlife Program includes many projects with the common objective of enhancing instream flows to benefit fish habitat and passage. These projects include irrigation efficiency projects (IE projects) that improve conveyance infrastructure by piping or lining canals and ditches, or that aim to improve application efficiency by irrigation system improvements such as converting from surface to sprinkler application. Other Council projects are water transactions projects (WT projects) that buy, lease or modify water rights to reduce irrigation diversions and increase instream flows.
While IE projects may be motivated by a desire to alter streamflow to protect fish, these projects can also affect power demand and downstream hydropower supply and timing which might affect the basin-level cost-effectiveness of these projects.
This report is motivated by the following questions:
- What has been the experience within the region, in terms of success and cost, with projects to improve irrigation efficiency for the purpose of altering streamflow for the benefit of fish?
- What has been the experience within the region, in terms of success and cost, with projects that have leased, bought, or otherwise modified water rights to alter streamflow for the benefit of fish?
- What conclusions can be drawn about the cost-effectiveness of alternative ways of modifying instream flows for the benefit of fish?
The next section of this report investigates and reports on general principles and experience regarding irrigation efficiency and infrastructure improvements for enhancing instream flow and fish habitat. Hydrologic principles, state laws regarding protection of saved water, and relationships between electricity and irrigation efficiency are discussed. The following section summarizes the irrigation efficiency and water transaction programs in the region, most of which are supported by the Fish and Wildlife Program (FWP). Information on costs and the amount of water acquired is provided.
The fourth section summarizes several case studies where IE and WT projects have been implemented to improve water conditions for fish. Factors such as the needs of fish, hydrology, the nature of irrigated agriculture, the size of the basin, the position of the project in the watershed, and the ability to protect flow are found to influence project success. The case studies are presented in more detail in the appendices. The final section summarizes and to the extent possible lays out the implications for cost effectiveness of both irrigation efficiency and water transaction projects.
