Verification and Testing of a Numerical Model for Evaluating Issues Related to Water Supply Reliability, Water Quality and Ecosystem Health
Excessive soil salinity in arid areas of the Western United States impacts water quality and eventually leads to land degradation. It is essential to implement drainage management practices, such as recycling of water resources, to control salinity. Several management strategies have evolved to help dispose of drainage waters. One strategy being adopted by growers in the San Joaquin Valley is Integrated Farm Drainage Management (IFDM) system, in which drainage water is collected and used sequentially to irrigate crops of increasing salinity tolerance. Currently the IFDM system is being demonstrated at Red Rock Ranch (RRR). There is a need to apply a numerical model to understand the hydrologic processes governing the IFDM systems and to evaluate the flow and salinity impacts to regional ground water systems.
* Will modeling of the RRR IFDM system elucidate the important design and operational parameters necessary to optimize the RRR system and future IFDM systems in the Western United States?
Need and Benefit
In arid lands of the Western United States, off-farm disposal of agricultural drainage water with high levels of salts and selenium degrades water quality of rivers and waterways, particularly the San Joaquin River and its tributaries. One of the management options that is designed to eliminate the need for off-farm disposal of drainage water is the IFDM system. This approach is designed to prevent the on-farm percolation of irrigation water to regional ground water, remove salts and selenium from the plant root zones, and conserve water supply by reducing the demand for irrigation water.
Reclamation's mission to stretch/enhance the western water supply can be achieved through conservation of water and prevention of the environmental damage by drainage water. It is therefore in the interest of Reclamation and western States to encourage the voluntary implementation of the IFDM systems as a means of improving environmental protection, conserving water, and restoring degraded soils.
For example, conservation of water and elimination of off-farm disposal of drainage water will reduce the volume of drainage water that is required to be disposed from the San Luis Unit by Reclamation. This will further translate into reduction of the volume of water supply used by Reclamation to address water quality issues in the San Joaquin River and the Delta, resulting in enhancement of the Reclamation water supply. A demonstration of an IFDM system is underway at Red Rock Ranch in the San Luis Unit. The HydroSphere fully-integrated modeling tool will be utilized to evaluate flow and transport in the IFDM system. This work will facilitate a thorough understanding of the coupled surface/subsurface flow and transport processes, and lead to optimal design of new IFDM systems and evaluation of effectiveness of existing systems to control drainage water and salinity in arid lands of the Western United States.
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