Guidelines for Sediment Control in Irrigation Return Flow

Sediments in irrigation return flows arise mostly from erosion in furrows during irrigation, and sediment concentrations vary widely from near zero to several thousand ppm. Reducing both erosion and runoff would decrease the sediment in return flows. Technology is available for reducing both erosion during irrigation and soil loss from the land, and for removing sediments from return flows. This technology is discussed, and the following guidelines are suggested. 1) Eliminate or reduce irrigation return flows when conditions permit using irrigation methods with little or no runoff. 2) Control the irrigation furrow slope so that the run is across the steepest slope or on the contour. Decrease the slope near the end of the furrow to reduce the flow velocity and increase sedimentation. 3) Control the furrow stream size and make proper stream adjustments. Adequate water measuring equipment and controls are essential for proper stream size control. 4) Shorten the run length. 5) Control the irrigation duration to reduce the number of irrigations per season. Alternate furrow irrigation reduces the contact between soil and flowing water and subsequent erosion. 6) Cultivate only when necessary, avoiding excessive soil loosening which increases erosion and soil loss. 7) Control tailwater by assuring that it flows slowly enough that sediments settle before the water leaves the field. Filtering through grass strips removes sediments. 8) Utilize sediment retention basins to remove sediment from return flows