Application of System Optimal Depth Concept

The concept of the system optimal depth (SOD) is applied to a power function cumulative water distribution that represents a wide range of irrigation practices. Either the interval between irrigations (when the application distribution is fixed) or the irrigation time (when the requirement is fixed) can be determined when the relative costs of excess irrigation and deficit irrigation are known along with the mean, maximum, and minimum applications for the water distribution. The SOD method is shown to be applicable to all irrigation methods; however, some current irrigation practices correspond to practices suggested by the SOD method, only when the costs of excess irrigation or deficit irrigation are relatively large. When the costs of excess and deficit irrigations are similar, the SOD method should be used to determine the appropriate operating procedure.