River basin salinity management via the ASTRAN method: II. Case study

Abstract

The accelerated salt transport ( astran) method for managing salinity in an irrigated stream-aquifer system is applied to the lower San Luis Rey River basin in southern California. The hierarchical management algorithm developed in Part I is applied for optimally implementing astran over the basin. Three subbasins are included in the study; Pauma, Pala and Bonsall. Unsaturated and saturated zone models for water quantity and quality are calibrated for the area, including important ions such as Ca 2+, Mg 2+ and Na + as well as SAR. Once the models have been satisfactorily calibrated, a 20-yr. planning period is selected which is divided into two 10-yr. model periods. Hydrologic, land-use, water-demand and water-supply projections are then made for each subbasin. The hierarchical algorithm is then applied, which results in a set of policies over a range of possible levels of total available imported water. For the same quantity of imported water, astran reduces the degradation rate by about one-fifth of what is projected under normal irrigation practice (called the no-management case). astran appears to perform best when the groundwater is allowed to degrade to higher, yet still usable, TDS levels.