Quantitative Assessment of Water and Salt Balance for Cropping Systems in Lower Colorado River irrigation Districts
Can crop production methods and irrigation methods used to conserve water during irrigation be counter productive and end up using more water due to the salinity in irrigation water and soil?
Effective leaching is especially important in the Lower Colorado River Basin because many of the crops produced are sensitive to salinity (Sanchez and Silvertooth, 1996). To reduce risk of loss of crop yield, there is some level of excess irrigation (beyond crop consumptive use) that must be applied to leach salts below the crop root zone. Evaluations and studies need to be conducted to have a reliable estimate of irrigation water quantity application necessary to accomplish effective leaching, while not using more water than necessary.
While there have been developments of irrigation scheduling recommendations for most of the crops in the region, the traditional computer-based approach developed is no longer compatible with the schedules or culture of most producers. Would development of an irrigation scheduling mobile application, based on Dr. Sanchez's AZSCHED database and algorithms, be more effective to reach producers?
Need and Benefit
Need: Reclamation encourages its customers/stakeholders to conserve water where they can. Reclamation has cost share programs that partially fund projects which would result in water conservation and, while irrigation districts in the Lower Colorado River Basin have some of the most efficient irrigation practices, some level of excess irrigation is needed to compensate for salts in the irrigation water and soil after fallowing. Southwestern Arizona and Southeastern California have soil and water salinity problems they are always working on and more information is needed to quantify how much water is required to leach salts without overirrigating beyond what is needed for crop consumptive use and removal of salts.
Benefit: If Reclamation, through partnered research, provides its customers/stakeholders with valuable decision-making data and tools, they will be even more efficient in their irrigation practices to conserve water without reducing their crop yield.
Urgency: Efficient water management and maximum productivity remains a high priority in the southwestern United States during an extended drought. In these efforts, stakeholders use irrigation water wisely, but there is a fine line between conserving water and risking soil health and reducing crop yield due to salts in the agricultural water and salts in the soils after a period of fallowing. If there is no clear understanding on water and salt balances during a growing season, the risks are that either too much water will be used (overirrigation) or not enough water will be used (excess salt within soils, reduced crop yield).
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Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
Quantitative Assessments of Water and Salt Balance for Cropping Systems in Lower Colorado River Irrigation Districts (final, PDF, 3.8MB)
By Paul Brierley, Charles Sanchez
Report completed on September 30, 2020