Spate Irrigation Systems and Watershed Development in Eritrea: the case of Sheeb watershed

This paper describes the interactions of the Spate Irrigation System (SIS) in Eritrea with their upper watersheds, as a case study in Sheeb watershed. The spate irrigation practices, among others, include techniques to harvest runoff water, sediments, and nutrients. A strong relationship exists between the SIS in the lowlands of Eritrea and their upper watersheds. For example, the spate irrigation system in the lowlands of Sheeb area entirely depends for water, soils and nutrients on the resources of its upper watershed. Interventions of soil and water conservation practices in the upper watershed could reduce soil loss and sedimentation rates, in the long term. And, this in turn, lowers the quantity of sediments and nutrients harvested in spate irrigated fields of Sheeb. However, the runoff volumes may not be affected much (by such conservation measures) mainly because of the steep topography of the upper watershed with shallow soils, which induces more runoff than infiltration into the soils. It can be concluded that the lessons learned from the Sheeb watershed will be very useful for planning watershed development projects in other spate irrigated areas of Eritrea and possibly in other parts of the world where similar systems are practice

A land suitability system for spate irrigation schemes in Eritrea

Spate irrigation is a system used for wetting land prior to planting. Use is made of seasonal rivers (wadis) producing flash floods in the uplands, which are directed by structures to irrigate fields in the lowlands. A land suitability system for spate irrigation schemes in Eritrea was studied in the Sheeb area of Eritrea with and without land improvements. The availability of floods and soil moisture were the major land use requirements for spate-irrigated sorghum and maize, while salinity hazard has only a minor effect in spate irrigation systems. The suitable land for spate irrigation in the Sheeb area is distributed as follows: 16% is highly to moderately suitable, 24% is moderately suitable and 17% is marginally suitable. About 40% of the study area was found to be currently unsuitable for spate irrigation mainly due to a lack of floodwater and poor soils. With improvements to the spate irrigation system, such as construction of permanent flood diversion structures, the area of land suitable for spate irrigation will expand. The land suitability system presented in this study could be applied in other spate irrigation schemes of Eritrea and perhaps in other countries als