Rainwater Harvesting Options to Support Off-Season Small-Scale Irrigation in Arid and Semi-arid Areas of Zimbabwe

Abstract

Rainwater harvesting involves the collection, storage and subsequent use of rainwater for domestic, agricultural and other livelihood activities. It consists of a wide range of technologies used to collect, store and provide water for use by humans and/or human activities such as irrigation and providing drinking water for livestock. In semi-arid areas of Zimbabwe, where rainfall is scarce and insufficient to sustain dryland crop production, rainwater harvesting can form the basis for irrigation in order to improve food security. Some rainwater harvesting and irrigation technologies that are currently in use in Zimbabwe include roof catchment systems, rock catchment systems, ground catchment systems, small dams and sand dams. Roof catchment systems collect water from roof surfaces into storage tanks or the place of use. Rock outcrops provide collecting surfaces for rainwater. Sand dams and small dams or weirs are constructed across streams and rivers to capture and store surface and subsurface flow. These various ways of harvesting rainwater can be linked to different irrigation technologies which include drip, sprinkler and flood irrigation systems. Farmers have adopted different pumping mechanisms to move water from storage to point of irrigation such as use of solar, fuel (petrol/diesel) and manual methods. Although it has been proven that these technologies are beneficial in the dry areas, most of these systems are not well developed and only a few of these technologies are operational. There is therefore need to promote RWHI and include other RWH methods such as roadside divergence ditches which are currently not being used in Zimbabwe.