What exactly is spate irrigation?

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Dear friends,

I am trying to understand spate irrigation systems in more detail.

Is spate irrigation similar to other flood irrigation and water harvesting systems?

"Bed bars" or bed stabilizers are recommended to be used in the channel beds, but what is their use?

Are they parallel or perpendicular to the flow?

Taxonomy

7 Answers

  1. One more research paper for you to look into- Agricultural Water Management in Ephemeral Rivers: Community Management in Spate Irrigation in Eritrea

    Spate irrigation is a type of water management that makes use of water from "spates", short duration floods. Spates - lasting from a few hours to a few days - are diverted from normally dry riverbeds and spread gently over agricultural land. After the land is inundated crops are sometimes sown immediately. Often the moisture is stored in the soil profile and used later. The spate irrigation systems support low economic value farming systems, usually cereals (sorghum, wheat, barley), oilseeds (mustard, castor, rapeseed), pulses (chickpea, clusterbean), but also cotton, cucurbits and even vegetables. Besides providing irrigation, spates recharge shallow groundwater (especially in river bed), they fill (cattle) ponds and they are used to spread water for pasture or forest land in some places. Says experts - http://www.agriculturesnetwork.org/magazines/global/farming-diversity/spate-irrigation-good-for-people-livestock-and

  2. It is mostly found in the Middle East, North Africa, West Asia, East Africa and parts of Latin America. Flood water from mountain catchments is diverted from river beds (wadi’s) and spread over large areas. Spate systems are very risk-prone. The uncertainty comes both from the unpredictable nature of the floods and the frequent changes to the river beds from which the water is diverted.

  4. It is a crop irrigation technique consisting of diverting seasonal stormwater from valleys, rivers, riverbeds and gullies by gravity onto farmland situated at a lower elevation than the flood water. The flood water is then diverted to the fields. This may be done by free intakes, by diversion spurs or by bunds. On the field, there are basically four methods ofwater distribution. Field-to-field distribution, individual field distribution and extensive or intensive distribution. After the land is inundated crops are sown, sometimes immediately, but often the moisture is stored in the soil profile and used later. 

  6. Thank you Editor for invitation of the useful question

    Spate irrigation is a type of water management unique to arid regions bordering highlands. Spate irrigation systems are among the most fascinating and complex resource management systems. It is common in South Asia, the Middle East, North Africa and the Horn of Africa. . Spate irrigation systems are generally situated in remote areas where there is deep-seated poverty and support systems are weak. Spate irrigation is an ancient form of water management, involving the diversion of flashy spate floods running off from mountainous catchments, using simple deflectors of bunds constructed from sand, stones and brushwood on the beds of normally dry wadis. This type of agriculture is very risk-prone and requires high levels of co-operation between farmers to divert and manage the distribution of flood flows.

    Uncertainty is a defining characteristic. The number and sequence of floods vary from one year to another. So do yields, which can be high however.
    A second important characteristic is that sedimentation is as important as water management. Rivers in spate lift and deposit huge quantities of sediment. As a result there is constant change in bed levels, in both the river system and the distribution network. The uncertainty, occurrence of high flood peaks and heavy sedimentation mean that conventional irrigation modernization approaches are inappropriate.

    Sudden floods, or spates, originate from sporadic rainfall in macro catchments. After the land is inundated, crops are sown – sometimes immediately, but often the moisture is stored in the soil profile and used later. Spate irrigation systems support farming systems – usually cereals and oilseed, but also cotton, pulses and even vegetables.

    Examples.

    The largest area under spate irrigation is in Pakistan (1,402,000 ha). There are also substantial areas in Somalia (150,000 ha), the Sudan (146,000 ha), Yemen (115,000 ha) , Algeria (110,000 ha), Ethiopia (100,000 ha) and Morocco (79,000 ha). 

  7. Hi Douglas,

    I am not an engineer.I am trained in social development/ communication and have been working with the Spate Irrigation Network for the past 5 years, and with communities practicing spate irrigation in Ethiopia and Sudan.

    My understanding is that what spate irrigation systems  aim to manage are seasonal flows in ephemeral rivers in semi-arid areas. The systems are about water diversion, but also about using seasonal water for as big a part of the year as possible. So soil moisture retention techniques (such as mulching), water use economy, choice of crops (water-efficient varieties), groundwater recharge (for use during dry seasons)... these are all elements of the 'system;' they make up the spate agronomy.

    I also notice that in spate systems the slope are in play much more than in systems based on flood water spreading. So you are dealing with much stronger flows and bigger sediments. 

    For more information please see our website (http://spate-irrigation.org/spate-irrigation-network/) 

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