ABSTRACT
The sustainability of spate-irrigated agriculture in a semi-arid climate depends on efficient use of irrigation water. Thus, efficient capture and storage of soil moisture in the field are crucial for sustained productivity. Unlike conventional irrigation which relies on less variable supply from perennial rivers, spate irrigation relies on highly variable water supply. In Gash agricultural scheme (GAS), water supply variability induces uncertainty in farming decisions due to unpredictable floods in terms of timing, volume and frequency. The border irrigation method is the most dominant technology for field water management in spate irrigation systems. This method is suitable for large-scale farming characterized by long uniformly graded strips and separated by earth bunds. Currently, GAS operates on a two-yearly rotation system in which the first half of the irrigation fields is irrigated in one season and the second half is left fallow to be irrigated the next season leaving the first half as fallow.
