HYDRAULICS OF IRRIGATION LATERALS - COMPARATIVE-ANALYSIS

A differential approach is applied to multiple outlet pipes with constant and continuously variable outflow. This approach simulates pressure distributions along uniform sprinkle and trickle irrigation laterals and manifolds, as well as gated pipes. The effect of ground slope and velocity head on the pipeline hydraulics were considered. An alternate simplified procedure that neglects velocity head effects and assumes that the lateral is laid on level ground is also included. Several mathematical relations are derived for computing maximum, minimum, and average pressure heads and their locations of occurrence along a lateral. The hydraulics of the common types of manually and mechanically moving sprinkler irrigation systems such as wheel line, linear move, and center-pivot systems are considered in the present analysis. When compared to pressures and locations of occurrence computed using a discretized, stepwise computation procedure, values computed using the developed equations are generally within 3% for maximum, minimum, and average pressures, and are generally within 5% for the locations of occurrence. The proposed equations are useful when applied for design and evaluation purposes.