|Ayars, James - Jim|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 7/8/2009
Publication Date: 3/14/2014
Citation: Ayars, J.E., Hanson, B.R. 2014. Integrated irrigation and drainage water management. In: Chang, A.C., Silva, D.B. editors. Salinity and drainage in the San Joaquin Valley, California: Science, Technology, Policy Global Issues in Water Policy 5. New York, NY: Springer p. 249-276. Interpretive Summary: Disposal of saline drainage water is the most significant problem facing irrigated agriculture on the West side of the San Joaquin Valley. After the closure of the Kesterson the reservoir, due to the bioaccumulation of selenium, farmers were left without any alternative for drainage water disposal. The state of California and the Federal government funded a 5-year research program to determine alternative strategies for drainage water disposal. This manuscript describes the summary of research related to irrigation and drainage water management that was done through the San Joaquin Valley Drainage Project supervised by the University of California. The results of these studies were incorporated into the overall final report published by the State of California and the US Bureau of Reclamation. The results of the irrigation studies demonstrated that significant reduction in drainage flow was achievable by improved irrigation management and switching from surface to pressurized irrigation systems. The research also demonstrated the potential for using subsurface drip irrigation in areas with shallow groundwater without requiring drainage. The drainage research identified reuse of saline drainage water for supplemental irrigation, and groundwater management as the principal components for source control and drainage water reduction. Implementation of improved irrigation system management and conversion to pressurized systems coupled with reusing drainage water, and improved groundwater management will be significant components in the solution of the drainage water disposal problem in the San Joaquin Valley.
Technical Abstract: Results from several research projects conducted in the 1990's are summarized in this manuscript. The first projects are irrigation studies that evaluated the impact of pre-plant irrigation water on crop water use and deep percolation losses. The results showed significant losses with pre-plant irrigation if the irrigation was not timed properly. Drip irrigation was evaluated as an alternative for surface irrigation and the results of several studies showed it to be effective in increasing yields of cotton and tomato and reducing deep percolation losses. Studies using subsurface drip on tomato demonstrated that it could be used in areas with shallow groundwater without requiring the installation of subsurface drainage systems. The one limitation on using subsurface drip was the need to have a fixed bed configuration for plants. The subsurface drip simulations using HYDRUS determined that adequate leaching occurs with subsurface irrigation and traditional methods of characterizing the leaching fraction are not valid. Drainage research in water table control and water reuse demonstrated that saline drainage water can be effectively used on salt tolerant crops such as cotton and sugarbeet without affecting yields. The presence of boron in drainage water represents a limitation when using it for irrigation because of the potential for plant damage. For groundwater control to be effective subsurface drainage systems have to be redesigned to allow control that will not result in water logging on the downstream end of system. Also, subsurface drainage systems will need to be designed to include control structures such as valves. Implementation of shallow groundwater management will require that irrigation scheduling be modified to include in in-situ use of groundwater by crops.