Surface Irrigation Degradation of Water Quality in Streams

Gravity fed irrigation systems were built in Malheur County, Oregon, in the early 20th century to serve intensive horticulture and livestock production.  Reservoirs, dirt canals, and surface systems were constructed relying on gravity fed water distribution and catchment and reuse of return flow.  Over the last forty years various programs have collected and analyzed water samples from throughout the intensely managed parts of the watersheds. Data were compiled and evaluated to examine how irrigation practices may affect surface water quality. The results demonstrate that water is enriched in total phosphorous, orthophosphate, E. coli, and dissolved solids. Options to reorganize water delivery systems are being studied and implemented. Innovative practices are being adopted at the producer level to mitigate the effects of irrigation induced erosion and runoff from farms.