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

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