Effect of Travel Time on Management of a Sequential Reuse Drainage Operation
- William A. Jury *,
- Atac Tuli and
- John Letey
Sequential reuse of agricultural drainage water recovered in tile lines has been proposed as a strategy for reducing drainage volume in the western San Joaquin Valley of California. In this system, high-quality water is used to grow a salt-sensitive crop, and the drainage from this operation is collected by tile lines and subsequently used on a more salt-tolerant crop. This process is continued on progressively more salt-tolerant species until the final residual is collected and sent to evaporation ponds. In this paper we develop a transfer function model for simulating the drainage concentrations of each stage of a sequential reuse project. Transient salt concentrations are calculated for typical drain spacings and water management strategies, under the assumption that downward movement of water is eventually restricted by a subsurface barrier. Results of the calculations show that response times of fields managed in this way are extremely long, so that the drain lines primarily capture resident ground water for decades or more after the operation is started, especially if the barrier is assumed to be at a substantial depth below the surface. As a result, the system will never reach steady state in any practical period of time, and system design strategies based on steady state behavior will be flawed.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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