Review of Water Harvesting Technologies for Food Security in Ethiopia: Challenges and Opportunities for the Research System

Abstract

Water harvesting has been promoted in Ethiopia on the basis of augmenting rainfed agriculture following 1971-1974 droughts in Tigray, Wollo and Hararge regions. A large number of water harvesting technologies have also been implemented with support from the Government. For instance, this assessment report indicated that more than 300, 000 shallow wells, about 206, 200 house hold level structural ponds, 49, 311 community ponds, 5,635 cisterns have been constructed and a total of 32, 727 springs have been developed.  But these works have not been proven as successful as expected, because of technical and socioeconomic problems.  The structural failures are connected with poor design, water lose due to evaporation and seepage, low technical capacity and subsequently low adoption by user. Another report indicated that there was only 22% functional water harvesting structures out of the constructed ones between the periods 2003-2004 in Amhara regional state.  The most critical of all the problems is the water loses due to seepage resulting from poor lining materials of the harvesting storage structures. Hence technologies providing good protection towards seepage loss have been given a priority. With a view of this, some research works have been conducted to identify the best lining materials that reduce water lose due to seepage. Accordingly, a study showed  that mortar performed best (1.4 mm/day) followed by salt with compaction (7.88 mm/day) and local ash (9.33 mm). Another study also concluded that the rich mixture (1:3 Cement to sand ratio) was better in controlling seepage rate than the lean mixture (1:5 cement to sand ratio). A study on local materials for seepage control showed  that the bio-plastic made up cow dung better reduced the seepage loss significantly (i.e. about 3.55 cm/day) than the untreated silt clay soil which had an observed 6.65 cm/day of seepage rate for a particular study site. The Ethiopian Institute of Agricultural Research has also now recently been working on the demonstration of low cost drip irrigation systems combined with water harvesting schemes for it has an advantage of greatly maximizing  water use efficiency and significant results have been  obtained in convincing farmers to use the combined technology .  For example, when combined with

drip irrigation, the use of shallow ground water becomes quite economical and the resource can be exploited on a sustainable manner for crop production . The use of such drip irrigation system permits reduction of water loss (up to 50%) as compared to flood irrigation showing water savings of 50% and a yield increase of 30%, with no substantial differences with the conventional drip irrigation systems .

In general, the importance of water harvesting works either in augmenting rainfed agriculture or supporting double cropping cannot be overemphasized as long as the critical problems resulting in the failure of the structures have been resolved. Thus identification of low cost and effective lining materials and promotion of low cost drip irrigation systems should be given top priority in order to extend those technologies with the fastest level of adoption.

Keywords: Water harvesting, lining material