As spate irrigation uses seasonal floods for irrigation, it is akin but different from two other categories of flood-based irrigation systems, i.e inundation canals (that start to flow as soon as the flood in a perennial river reaches a certain level) or flood rise or recession irrigation, where a rising perenial river overtops its banks and inundates the plains alongside the river. In flood rise or recession irrigation crops are grown on the rising or receding flow or on the residual moisture. In spate irrigation instead water is diverted from normally dry river beds (wadi’s) when the river is in spate. The flood water is then diverted to the fields. This may be done by free intakes, by diversion spurs or by bunds, that are build across the river bed. The flood water – typically lasting a few hours or a few days – is channeled through a network of primary, secondary and sometimes tertiary flood channels. Command areas may range from anything between a few hectares to over 25,000 hectares.
An example is shown in the video below. This video provides a snapshot of first floods in a seasonal river in Dayu Kebele, Raya Alamata Woreda in Ethiopia’s northern Tigray province. The seasonal floods are key to irrigation, groundwater recharge, and rural livelihoods in the region.