Linked models for managing river basin salt balance

Abstract

One of the pressing problems facing the irrigation intensive areas of the world is the increasing salinity of groundwater. A cost‐effective salinity management technique, called the accelerated salt transport (Astran) method, has been developed which may be feasible for many stream aquifer systems. The basic idea is to encourage application of pumped water downstream of the well from which it is pumped rather than within its vicinity. In this way a mechanism is established for accelerating the downstream transport of salts in the groundwater at a more rapid rate than would occur naturally through convection and dispersion while still satisfying irrigation demands. A management algorithm is developed for implementing the Astran method which combines an optimizing model with a detailed quantity‐quality simulation model. The optimizing model generates least‐cost alternatives for distributing water over the basin. These alternatives are subsequently examined by the simulation model as to their effectiveness in controlling the salt balance. A parameter in the optimizing model can be adjusted so as to produce a desired degree of salinity control. The management algorithm has been applied to the Bonsall Subbasin in the San Luis Rey River Basin in order to test its effectiveness. Results of the case study indicate that the Astran method (1) is cost‐effective, requiring roughly 10% of the cost of tiling for this area, (2) encourages balanced conjunctive use of surface water and groundwater, and (3) is flexible enough to respond to future management needs.