Design criteria for microcatchment water harvesting with scarce data

The harvesting of surface runoff water for irrigation use is discussed. Design, construction and operation of these schemes is a hydrological and engineering problem, however, social, political, economical and environmental factors also need to be considered. The design of such a system for microcatchment areas is described. Surface water from an area of 100 to 500 square metres is collected, stored and used in a small infiltration basin where the crops, etc., are grown. A model has been developed for predicting the volume of the runoff from a flat terrain microcatchment subject to nonuniform rainfall intensity and certain intitial soil conditions. It is derived from the kinematic overland flow equations and uses the Manning Equation as an approximation of the momentum equation. Results of field tests and comparisons with model simulations are presented. (J.M.M.)