Publication Summary

The Washington State Department of Ecology established a technical work-group to assist in developing recommendations for criteria to protect agricultural supply waters. This paper documents the discussions of that technical work-group and the basis for recommended water quality criteria. It includes the cover decision memorandum.

The Washington State Department of Ecology established a technical work-group to assist in developing recommendations for criteria to protect agricultural supply waters. This paper documents the discussions of that technical work-group and the basis for recommended water quality criteria. This paper is intended to help the public understand and comment on the recommended criteria. If adopted, the criteria would apply to all waterbodies that have agricultural water supply established as a designated use. Criteria to protect agricultural supply would not, however, apply at individual points of use within irrigation projects that are designed to capture and reuse drainage waters from the individual agricultural operations. The recommendations proposed include both general narrative criteria to prevent deleterious effects plus numeric limits for a select list of water quality constituents. The constituents for which numeric criteria are being recommended include electrical conductivity, bicarbonate, total suspended solids, radioactive materials, and pH. Since use of waters for irrigated agriculture is widespread, the proposed criteria will also be broadly applied to rivers, lakes, and reservoirs throughout the state.

The criteria are established to provide a moderate to high level of protection for soils, crops, and irrigation equipment. While the technical work-group assisted in evaluating potential water quality criteria, they were generally opposed to Ecology establishing any criteria. The common opinion of the work-group was that establishing criteria to protect agricultural water supplies was unnecessary since most water supplies currently meet the proposed criteria and irrigation water quality is not a significant concern of farmers. Ecology recognizes that the proposed criteria are largely preventative in nature, but also believes that maintaining high quality water supplies is important. The proposed criteria should help prevent the economic and social costs associated with deterioration in water quality; providing benefits to Washington′s farmers long into the future.