Interrelationships of Irrigation Uniformity Terms

Abstract

Irrigation uniformities are examined for six assumed statistical distributions of depth of water infiltrated. Christiansen's uniformity (UC) and the lower quarter distribution uniformity (DU) are related analytically to the coefficient of variability (CV) in each case. The distributions chosen are the normal, log normal, uniform, a specialized power, beta and gamma distributions. In all cases studied, for CV values of less than 25%, approximate forms of UC and DU were found valid. Three examples are given using the specialized power and beta distribution. It is demonstrated that the specialized power function is exact for level basin irrigation provided the surface water advance is proportional to a power of time and the intake rate everywhere has approached a constant value before recession.