Publication Summary

The Department of Ecology regulates the use of copper in irrigation canals through a National Pollutant Discharge Elimination System permit. To evaluate the effectiveness of discharge limits set in the permit, surface water and sediment samples for copper were collected in two irrigation projects that discharge to the Mid-Columbia and Wenatchee Rivers. None of the water samples exceeded Washington State water quality standards for copper. None of the sediment samples exceeded available sediment quality guidelines for copper. Data collected showed that there is little potential for adverse impacts to aquatic and sediment-dwelling organisms from copper in the areas sampled.

The Washington State Department of Ecology (Ecology) regulates the use of copper herbicides in irrigation canals through a National Pollutant Discharge Elimination System (NPDES) permit. In order to evaluate the effectiveness of discharge limits set in the permit, Ecology conducted surface water and sediment monitoring to measure copper concentrations in two irrigation project areas during 2007-08.

The Mid-Columbia Irrigation and Wenatchee Reclamation project areas were sampled in three types of locations: above irrigation project inputs, near a major outfall (Shop Spillway and Ringold Canal), and downstream of irrigation project inputs.

In each irrigation project area, samples were collected in rivers that receive discharge from irrigation canals. Surface water samples were collected in the Mid-Columbia River and the Wenatchee River before and after irrigation operations and two times during the maximum use period for copper. Sediment samples were collected in both rivers before and after irrigation operations.

None of the water samples were found to be above Washington State Water Quality Standards. In the majority of the samples, copper was found to be in the dissolved form which makes it biologically available.

No Washington State standards have been established for freshwater sediments. Therefore, the data were compared to proposed sediment quality values and a Canada interim sediment quality guideline. None of the sediment samples contained copper concentrations above these guidelines. Conventional parameters for sediment showed that there was not much fine-grained sediment available for copper to adsorb to.

Data collected showed that there is little potential for adverse impacts to aquatic and sediment-dwelling organisms in the areas sampled.

Link to EIM data for User Study ID CBUR0007