Control of Sediments, Nutrients, and Adsorbed Biocides in Surface Irrigation Return Flows

The technology available for the control of sediments, nutrients, and adsorbed biocides in surface irrigation return flows has been reviewed and evaluated. Some of this technology could be applied immediately to reduce sediment and associated nutrient and biocide concentrations in surface irrigation return flows. Much of the available information needs to be integrated to develop improved control practices. New ideas and new control technology are needed. Economic incentive programs are needed to improve acceptance of control technology. The factors controlling erosion and subsequent sediment concentrations in surface irrigation return flows, and how these factors can be managed to reduce erosion and sediment concentrations are reviewed and discussed. Three approaches (1) eliminating surface runoff, (2) reducing or eliminating erosion, and (3) removing sediments and associated nutrients and biocides from surface irrigation return flows, and control measures for each approach are discussed. Research and demonstration needs for improving and developing new control technology are presented. These include simulation modeling of known erosion parameters, the development of improved irrigation systems and methods, the design of improved irrigation water distribution systems, and field management practices. The need for more information on design and operational criteria for sediment retention basins is discussed