ABSTRACT
In arid and semi-arid areas the source of shallow groundwater being used in an integrated system is generally deep percolation from irriga tion on the subject field or lateral flow from an adjacent field. Rainfall amounts in these areas are generally small and add little water, if any, to shallow ground water. For example, the west side of the San Joaquin Valley, California, receives, on average, 150 mm of rainfall each year, generally during the winter months with average rainfall events of 5 mm or less, which do not result in deep percolation. Since rainfall is not a significant contributor to the total water supply, it is possible to estimate the potential shallow groundwater supply based on the water requirements of the crop rotation and the irrigation system efficiency and management practices.
