Analysis of Spate Irrigation Sedimentation

Spate Irrigation is a type of runoff farming where flash floods produced in the highlands are diverted by irrigation structures to irrigate fields. The farmers in the southern part of Tigray have long been diverting traditionally the flash floods into their irrigated fields. However the indigenous spate irrigation practices have many problems such as the destruction of headworks during large flood events. Hence the regional government of Tigray has shouldered the responsibility to modernize these spate schemes. However the majority of the schemes are not effective the main problem being sedimentation of canals and irrigated fields. Sedimentation highly affects the operation of the scheme; coarser sediments reduce the diversion efficiency of the scheme and raise the bed level of irrigated field. Contrary to this fine sediments improve the fertility of spate irrigated fields. Therefore to compromise between these effective sediment control and management that enables the trapping of coarser sediments before reaching the irrigated field and allows the fine sediments to reach into the irrigated fields should be implemented