Irrigation goes into orbit
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CTA. 1993. Irrigation goes into orbit. Spore 45. CTA, Wageningen, The Netherlands.
Permanent link to this item: http://hdl.handle.net/10568/49136
Runoff irrigation in the Sahel zone by W Tauer and G Humborg 1992 192pp ISBN 3 8236 1212 3 CTA
A major constraint to agricultural development in semiarid areas, such as the Sahel, is the extreme variability of the distribution of water over both time and space, rainfall being almost the only source of available water. Runoff irrigation, that is irrigation using rainfall without any form of temporary storage, is one way of improving the use of scarce and variable rainfall. The Institut fur Wasserbau and Kulturtechnik, at the University of Karlsruhe in Germany, has maintained a research team in the village of Kanguessanou north-east of Kayes, Mali, since 1985 in order to study agricultural systems using runoff irrigation. Successes achieved at a number of sites in the locality and at a site in northern Burkina Faso have been documented in Runoff irrigation in the Sahel zone by Wolfram Tauer and Hans Georg Humborg. CTA has financed the publication of this book as part of its commitment to ensure that developing countries have access to high level scientific information. The authors explain that in order to identify areas where there is potential for runoff irrigation, a number of factors besides the obvious ones of rainfall and topography need to be considered. These include vegetation, agricultural practice, soils, sociology and infrastructure. In regions such as the Sahel, the lack of up-to-date topographical ordinance maps of less than 1:200,000 or even their total lack, creates complications because no comprehensive information is available. Remote sensing using satellite imaging has been found to be the most effective way of obtaining at least some of this information over areas much greater than could ever be covered by field visits. Satellite imaging is also cheaper than aerial photography. Remote sensing can be used, for example, to indicate the capacity of the soil to store water. This is achieved indirectly by a study of the density of vegetation cover. The principles underlying the interpretation of satellite images are explained in detail in the book, although it is emphasized that remote sensing is not a replacement for 'ground truth' or field visits. Following a comprehensive technical review of all the available hydrologic models and mathematical approaches currently in use for determining the rainfall-runoff relationship, the authors suggest that the '\E9tats de surface' model appears to be the most promising for determining water harvest potential. This is because it has been developed especially for West African conditions and it requires only the rainfall depth as the meterological input data. This model can also be adapted to make use of hydrologic assessment from high resolution remote sensing systems. Satellite data is the prime, if not the sole, up-to-date source of information in the Sahel countries. Computer technology is being developed to permit ever more rapid and more detailed interpretation of data. It is to be hoped that this sophisticated level of scientific information can be used to get more water on to farmers' crops in the resource-poor semi-arid lands of the Sahel. Runoff irrigation in the Sahel zone by W Tauer and G Humborg 1992 192pp ISBN 3 8236 1212 3 CTA