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The extreme variability in rainfall makes agriculture in Ethiopia equally extreme to manage. Drought has caused partial or complete crop failure in the semi-arid and dry sub-humid parts of the country, while flooding has washed away fertile top soil and displaced hundreds of thousands of people. Climate change is likely to reinforce this even further in the coming decades.
Rainwater harvesting, a method for collecting rainfall for domestic or agricultural use, has been hailed as a way to turn these inherent challenges of rainfall variability into opportunities rather than obstacles. Indeed, water harvesting investments have been central to Ethiopia’s National Food Security Strategy, but implementation has often failed due to inadequate analysis of areas that are suitable for this investment.
A new study conducted by former centre PHD student Yihun Dile together with centre director Johan Rockström and Louise Karlberg from the Stockholm Environment Institute presents the first suitability analysis for water harvesting in the Upper Blue Nile Basin in Ethiopia.
Their result is uplifting.
“The suitability analysis carried out in this study has shown that the Upper Blue Nile Basin has a large potential for water harvesting”
Yihun Dile, lead author
In the study, Dile and his colleagues applied two different data processing tools to assess the suitability of different areas in the basin. The first, Boolean MCE analysis, identified locations based on a highly cautious and conservative strategy where only cultivated land areas that receive an average rainfall of 200 to 1200 mm were considered. This specific boundary is because areas with rainfall less than 200 mm are arid regions with low population and a high risk of production failure. The second analysis, weighted overlay, took a closer look at the identified areas and helped indicate what kind of approach could be used for water harvesting.
Dile and his colleagues found that the area classified as most suitable covers 6-24% of the land while more than 50% of the study area is moderately suitable, particularly around Lake Tana in the north and in the eastern part of the study area.
The illustration shows suitability for water harvesting either by trapping and retaining the rainfall water in the root zone of the soil where it falls (in situ) or water capture areas external to the point of water storage (ex situ).
Remember to consult stakeholders
The results from the study used biophysical data to identify suitable areas for water harvesting. The next step according to the authors, is to consider various socio-economic analyses and stakeholder consultations. Only then will you have a robust suitability water harvest analysis, they say.
"Access to markets, labour availability, gender and education are among the key determinants of water harvesting implementation which require thorough consideration," says co-author Louise Karlberg.
Furthermore, stakeholder consultation can help to cross-check the feasibility of identified water harvesting systems with the local context.
"Engaging the stakeholders, creates ownership of the projects, which increases the sense of responsibility for taking care of the systems. This, in turn, increases the chances of success," the authors conclude.
Dile, Y.T., Rockström, J., Karlberg, L., 2016. Suitability of Water Harvesting in the Upper Blue Nile Basin, Ethiopia: A First Step towards a Mesoscale Hydrological Modeling Framework. Adv. Meteorol. 2016, 12. doi:ttp://dx.doi.org/10.1155/2016/5935430
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