Soil Salinity and Drainage Requirement Using Recycled Drainwater for Crops
* How can reuse areas be designed and managed to provide an effective alternative to traditional agricultural drainage disposal?
Reclamation is conducting a feasibility study to provide a solution to the historic drainage problems of the San Luis Unit in California. The current plan calls for collection and reuse of all agricultural drain discharge. This will require about 10, 000 acres of new drain water reuse development to handle the drainage flows. The Panoche Drainage District, a part of the San Luis Unit, has been operating an 1, 800-acre drainage reuse facility for several years (start in 1998) using shallow subsurface drains to provide water table and salinity control. This research will be used to evaluate the effectiveness of their drainage system, and the changes in soil salinity when using high total dissolved solids (TDS) drain water as the irrigation supply. This research will provide a better understanding of design and long term operation and maintenance (O&M) considerations for reuse as an alternative to agricultural drain discharge.
Need and Benefit
Traditional irrigation uses water that has a much lower salinity than collected drainage water. The higher saline drainage water can be used to irrigate salt-tolerant crops, resulting in reduced final drainage discharge, but higher soil salinity. The large-scale use of the drain water has not been on a project-wide basis and does require some special measures to ensure long term productivity of the reuse fields. Drainage is a key component to the long term success of drainage reuse. Reclamation has not developed a drain water reuse site and can benefit from examining the existing Panoche Drainage District reuse operations. Depending upon what the Panoche data show, new criteria or standards for drainage and soil salinity under reuse conditions could be established.
Successful drain-water reuse, as an alternative to traditional discharge for the San Luis Unit, will prevent agricultural drain water from entering the streams and rivers. The existing reuse area at Panoche lacks monitoring data on the drainage system and the soil salinity changes. Operations and management of a drain water reuse facility have not been attempted by Reclamation, but could become an alternative to traditional drainage discharge on other Reclamation projects.
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