Submitted to: American Society of Civil Engineers
Publication Type: Proceedings
Publication Acceptance Date: March 10, 1996
Publication Date: N/A
Interpretive Summary: Shallow ground water is being recognized both in humid and arid areas as a supplemental water supply for crops. Shallow ground water management techniques have been developed for humid areas but not for arid areas. Soil salinization and plant salt tolerance criteria have been the major concerns which limited the development of shallow ground water management in arid irrigated areas. Improved irrigation water management techniques, new plant salt tolerance data, limited water supplies, and new surface water quality criteria have been factors in developing shallow ground water management methods in arid areas. Several techniques are available to manage shallow ground water. Flow from existing drainage systems can be restricted or stopped which maintains higher water tables and permits crop water use from shallow ground water. Crop use from shallow ground water can be induced by modifying irrigation schedules. Changing drainage design criteria and installation of future drainage systems to bring the water table closer to the soil surface is another alternative. Use of these techniques will result in improved irrigation water management and reductions in surface water pollution due to reductions in saline drain water discharge.
Technical Abstract: General descriptions of shallow ground water management are active and passive. Active techniques include any method which can be used to modify the water table position. Passive techniques are management alternatives which have an effect on the water table but not one that is not well defined or controlled. An example of an active method is the installation of controls on a subsurface drainage system to restrict flow from the laterals and reduce the depth to the water table which enables longer crop use. Recent studies in arid irrigated areas have shown this to be a feasible method. Installing the drains at shallower depths and relaxing the depth to water table criterion is another active method of shallow ground water management. Modifying the irrigation schedule is a passive method to induce crop uptake from shallow ground water. Recent studies have developed crop coefficients for cotton which account for crop use from shallow ground water and extends the irrigation interval. Field studies of shallow ground water management using cotton and tomato crops have demonstrated reduced irrigation amounts while maintaining yields and quality.