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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVED WATER RESOURCES MANAGEMENT FOR IRRIGATED AGRICULTURE IN THE PACIFIC NORTHWEST

Location: Northwest Irrigation and Soils Research

Title: Soil and Nutrient Losses from Small Sprinkler and Furrow Irrigated Watersheds in Southern Idaho

Authors
item Bjorneberg, David
item King, Bradley
item Nelson, Nathan -
item Lee, Joon Hee

Submitted to: International Irrigation Show
Publication Type: Proceedings
Publication Acceptance Date: October 21, 2009
Publication Date: N/A

Interpretive Summary: Sediment and associated nutrients flowing to the Snake River with furrow irrigation runoff and unused irrigation water have been a concern in the Twin Falls irrigation tract in southern Idaho. Converting furrow irrigated fields to sprinkler irrigation is one practice that has been promoted, and received financial assistance, to reduce sediment loss. Five small watersheds (330 to 1480 acres) with 10 to 70% sprinkler irrigation were monitored from 2005 to 2008 to determine if converting to sprinkler irrigation reduced sediment and nutrient losses from these watersheds. Eliminating runoff from furrow irrigated fields by converting to sprinkler irrigation will reduce sediment and nutrient losses from fields. However, there were no significant correlations between the amount of sprinkler irrigation and the sediment or nutrient loads from these watersheds. Potential reasons for these results are the flow rate allocation system used by the irrigation district, the amount and location of furrow irrigated fields in each watershed, and the management of furrow irrigated fields within each watershed. However there was a trend for dissolved phosphorus concentrations to decrease as the relative amount of sprinkler irrigated land increased in each watershed, presumably because less water flowed across fields in furrows as sprinkler irrigated area increased. A water quality model for irrigated watersheds is needed for more thorough assessment of the variety of conditions and management practices within these watersheds.

Technical Abstract: Sediment and associated nutrients flowing to the Snake River with furrow irrigation runoff and unused irrigation water have been a concern in the Twin Falls irrigation tract in southern Idaho. Converting furrow irrigated fields to sprinkler irrigation is one practice that has been promoted, and received financial assistance, to reduce sediment loss. Five small watersheds (330 to 1480 acres) with 10 to 70% sprinkler irrigation were monitored from 2005 to 2008 to determine if converting to sprinkler irrigation reduced sediment and nutrient losses from these watersheds. Eliminating runoff from furrow irrigated fields by converting to sprinkler irrigation will reduce sediment and nutrient losses from fields. However, there were no significant correlations between the amount of sprinkler irrigation and the sediment or nutrient loads from these watersheds. Potential reasons for these results are the flow rate allocation system used by the irrigation district, the amount and location of furrow irrigated fields in each watershed, and the management of furrow irrigated fields within each watershed. However there was a trend for dissolved phosphorus concentrations to decrease as the relative amount of sprinkler irrigated land increased in each watershed, presumably because less water flowed across fields in furrows as sprinkler irrigated area increased. A water quality model for irrigated watersheds is needed for more thorough assessment of the variety of conditions and management practices within these watersheds.

Last Modified: 8/22/2014
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