|Ayars, James - Jim|
Submitted to: Journal of Irrigation and Drainage Systems
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/1/2002
Publication Date: 10/1/2002
Citation: Hanson, B.R., Ayars, J.E. 2002. Strategies for reducing deep percolation in irrigated agriculture. Journal of Irrigation and Drainage Systems. Vol. 16(4):261-277. Interpretive Summary: Disposal of saline drainage water is one of the major problems facing irrigated agriculture throughout the world. Drainage water may contain nutrients, pesticides, salt, and toxic trace elements, so there is a need to minimize the total flow from drains. It is not possible to totally eliminate drainage flow because of the need to manage salinity in the root zone. It is possible to significantly reduce the total flow through improved irrigation management and improved drainage system design and management. This manuscript summarizes the results of studies conducted in the San Joaquin Valley of California that focused on reducing deep percolation losses in irrigated agriculture. In general, it was found that deep percolation losses in surface irrigation could be reduced by improved management such as reducing run length, shorten set times, surge irrigation, and tail water recovery. Deep percolation was reduced with pressurized systems if these systems were properly designed and operated. Irrigation in the presence of shallow ground water was improved if the ground water contribution to crop water use was included in the irrigation scheduling process. Economics play a significant role in system selection and operation and system upgrades were only considered if it was economic.
Technical Abstract: The traditional approach of installing subsurface drainage systems to solve shallow ground water problems is not feasible along the west side of the San Joaquin Valley of California because of the lack of drain water disposal methods that are economical, technically feasible, and environmentally friendly. Thus, options such as drainage reduction through improved irrigation management and drain water reuse were examined as methods for coping with the subsurface drainage water disposal problem. This paper discusses options for reducing subsurface drainage water volume through improved irrigation practices such as upgrading existing irrigation methods and converting to systems with higher potential irrigation efficiencies. Methods for improving water management through irrigation scheduling and drainage system management are discussed. Case sutdies on upgrading exsiting systems or converting to other irrigation methods are presented along with study results of the effect of various policies on reducing subsurface drainage.