Irrigation Return Flow Water Quality in the Twin Falls and Northside Irrigation Tracts

Irrigation Return Flow Water Quality in the Twin Falls and Northside Tracts. A Thesis presented in partial fulfillment of the requirements for the Degree of Master of Science with a Major in Civil Engineering in the College of Graduate Studies University of Idaho, Moscow, Idaho.

Abstract

Irrigation return flows from the Twin Falls and Northside Canal Companies convey sediment and nutrients to the Middle Snake River, a water quality "limited" stream. A water quality monitoring network was established to document the sediment and nutrient loads on sixteen irrigation return flows during the 1995 irrigation season. Approximately, 18,153 tons of suspend sediment, 5.0 tons of ammonia nitrogen, 74 tons of organic nitrogen of which 5.0 tons was ammonia nitrogen, 108 tons of nitrite+nitrate nitrogen, and 36 of total phosphorus of of which 11.6 tons was dissolved ortho phosphate was discharged from these drains into the Middle Snake River. These loads were compared to baseline loads from the same irrigation return flows in 90-91. As part of a management plan, the canal companies have actively developing water quality facilities to treat irrigation return flows. A procedure was developed to determine the effect of these water quality facilities on sediment loading from the Twin Falls and Northside Irrigation Tracts. On the sixteen monitored drains, it was estimated that the sediment loading can be reduced 47% from the 1990-91 levels and 39% from the 1995 levels through the implementation of water quality facilities.

Availability

This thesis is available from the College of Graduate Studies, University of Idaho, Moscow, Idaho, 83844-3017.

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