Gravity-fed drip irrigation system for hilly terraces of the northwest Himalayas

Development of small tanks lined with low-density polyethylene film has provided irrigation facilities on the upland areas of hills on a limited scale. To utilise the scarcely available water, a gravity drip irrigation system was designed for the hilly terraces. The system had the capability to provide uniform emitter discharge throughout the command area spread on several terraces with varying elevations and irregular shapes. The design includes the estimation of the command area of the tank (runoff or low discharge spring-fed) using data on rainfall, evaporation and crop water requirement, and the hydraulics of the drip irrigation system. A useful and more pertinent star configuration of microtube layout with one lateral line feeding four rows was devised which had some advantages over the traditional layouts in terms of achieving the desired discharge rate, better handling of the system, appropriate water delivery, adjustment in spatial head variation due to friction loss in pipes as well as field slopes, and economic factors. Pilot testing of the system showed that the system worked efficiently, with field emission uniformity above 90%. Although the design criteria were developed for the topographical and climatic conditions of the mid-hills of the north-west Himalayas, they can easily be adapted for other locations.