Best practices for rainwater management in the Ethiopian Blue Nile are well known. They include many practices related to crop livestock and trees that increase water availability or productivity within the watersheds, such as soil and water conservation, small scale irrigation, fertility management, or livestock management. Nonetheless, adoption of many of these practices is still low, mainly because they have been promoted in locations where they are not suitable, or have not been combined with symbiotic practices that would result into real benefits for farmers.
Rainwater management practices therefore need to be combined at landscape scale to form rainwater management strategies. These strategies fit a specific context that is defined by the bio-physical, socio-economic and institutional constraints. In other terms, best bet rainwater management strategies are location-specific and best practices should be combined differently in different locations.
In geographic information systems (GIS), suitability analysis is a procedure that allows to select locations where a given practice is suitable. It is a four-step procedure :
- Selecting bio-physical suitability criteria
- Selecting the geographical layers that represent the bio-physical suitability criteria
- For each criteria, selecting location from the geographical layer where the criteria is met (in other words, creating criterion maps)
- Selecting all locations where all criteria are met (overlaying criterion maps) and creating practice suitability maps
For the Nile basin, adoption maps were created, based on economic models. These show the percentage of farmers that are predicted to adopt a practice, given the socio-economic and institutional constraints. When the suitability maps are overlaid with adoption maps, a feasibility map is created that shows how many farmers will likely adopt the technology on a suitable location allowing to prioritize locations with suitable socio-economic conditions.
The Nile Goblet tool
The Nile Goblet tool (also presented here) is an open source GIS tool that allows easily to make suitability and feasibility maps without prior GIS knowledge. It is a very flexible tool that in principle allows to map any practice for any location of the world, and helps consider combinations of practices. A database has been developed which includes all the (freely) available layers for the Nile basin, as well as the suitability thresholds suggested by the “integrated participatory watershed management guidelines” from the Ministry of Water and Energy.
Using the results of the tool on the ground
The maps resulting from the tool can be very inaccurate, due to the scale and inaccuracy of the input data. As such the maps present windows of opportunities based on expert knowledge of what communities could do. Action on the ground should help unlock local knowledge and complete this picture. Implementation should therefore be done in a participatory manner for instance with approaches such as the ‘happy strategies’ game. It can enable a dialogue between communities, non-governmental organizations and local government agencies around rainwater management practices, so as to validate the maps and come up with a feasible plan on the ground.
Offering a tool that allows policy-makers and practitioners to introduce their own or expert knowledge about suitability criteria into a transparent procedure will help them understand and trust the resulting maps, better understand why promotion of rainwater management should be location-specific and move away from today’s blanket approaches. Indeed, the resulting maps can support the elaboration of context-specific policies. In combination with the happy strategies game, the maps also enable expert knowledge to blend into a participatory approach and improve the planning on the ground with communities.