San Joaquin Valley Drainage Implementation Program, Draft Report, February 1998

The San Joaquin Valley in western USA is a long established region of intense irrigated agriculture with a valuable regional economy. Shallow groundwaters and accumulation of salt in the soil and groundwater from irrigation applications have affected crop production and the regional economy. Subsurface horizontal drainage of saline groundwater has traditionally been discharged to the San Joaquin River, evaporation ponds or the Kesterton Reservoir. However high conceetrations of selenium as well as other elements provided a threat to waterfowl in the Reservoir.
The recognition of the hazard to the waterfowl at Kesterton prevented drainage management and a change in the approach to the salt and drainage problems was required. An updated plan was established which included control of source water management, drainage re-use, evaporation systems, land retirement, groundwater management, and discharge to the River.

As this is a major irrigation area, the hydraulic issues are not directly transferable to the dryland situation in Australia. However, the off-site environmental impacts of drainage works need to be clearly understood as groundwater and surface water is exported by drainage activities. Revision of the management plan, institutional changes and monitoring of both the physical system and the plan implementation are essential.
A key issue, as yet not resolved is that of land retirement. There is some community opposition to land retirement because of the impact on the local economy, while there are other growers who are prepared to retire land to help solve drainage problems. However state funds for land retirement have been withdrawn.