AN ALGORITHM FOR OPTIMIZING RESERVOIR SIZE AND TOTAL COMMAND CULTIVATED AREA FOR SMALL SCALE WATER HARVESTING SYSTEMS

Abstract

The problem of water shortage in arid and semi-arid regions is one due to low rainfall and uneven distribution throughout the season, which makes rain fed agriculture a risky enterprise. Rain water harvesting for dry-land agriculture is a traditional water management technology to ease future water scarcity in many arid and semi-arid regions of world. Rainwater harvesting (RWH) is a method of inducing, collecting, storing and conserving local surface runoff for agricultural production. This study presents a brief treatise, of rainwater harvesting, and its historical perspectives. Optimum reservoir capacity is reported to be estimated by the tedious graphical method. In this study an alternative procedure is presented for determining the optimum reservoir size for supplemental irrigation of multiple crops using a water balance algorithm. It includes the short-term real-time reservoir operation model is developed for irrigation. Integration of reservoir operation with on-farm utilization of water by crops is achieved through the use of two methods: An operating policy model, which optimizes reservoir releases across time periods, and an allocation procedure which optimizes irrigation allocations across crops within a time period of the storage .The volume of water stored depends on the available runoff during the time interval considered along the rainy season, (user defined) and the water demand, which also varies depending crop type and its stage of growth (model predicted). Rate of sedimentation and useful life time of a reservoir were estimated using the trap efficiency (Te) approach.