SIMULATING SALINE WATER MANAGEMENT STRATEGIES WITH APPLICATION TO ARID-REGION AGROFORESTRY

Irrigation projects have greatly increased agricultural productivity in arid and semiarid regions, but they frequently contribute as well to saline high water tables, which must be mitigated by a drainage system. Drainage waters, sometimes contaminated by toxic elements, can lead to environmental degradation if not properly managed. One option is to irrigate salt-tolerant plants with drainage water to further increase the salt concentration while reducing the volume that would ultimately require treatment or disposal. Transient and steady-state models were used to simulate the consequences of applying saline drainage water to eucalyptus trees (Eucalyptus camaldulensis) under conditions typical to the San Joaquin Valley of California. Simulated results agreed well with limited field data. High evapotranspiration and large tree growth require application of large amounts of water, leading to large, deep percolation volumes. Degradation of soil physical properties by saline water could reduce the transmission of water through soil. This limits the quantities of irrigation water that can be applied, with consequent poor tree growth and low evapotranspiration.