Project information


Concept and project objectives

Water productivity  in Africa is the lowest in the world, and is further stressed by a rapidly growing population and the challenges posed by climate change. Africa contains about nine percent of global freshwater, and is characterised by large disparities in rainfall distribution and water availability across the continent (Joto Africa, 2009). Considering that Africa currently hosts almost 15% of the world’s population which is projected to increase to 17.5% by 2025 (UN, 2008), it is clear that relative water scarcity is on the increase. Africa is moreover the only continent where growth of food production has not kept pace with population growth in recent decades; yet performance of the agricultural sector is crucial for long-term growth prospects (UNECA, AU and AfDB, 2000), not least because 80% of Africans rely on agriculture for their livelihoods (Alliance for a Green Revolution in Africa, 2009).

The vast majority of African farmers rely on rainfall for food production: 95% of agricultural production in Africa comes from rainfed areas (UNEP, 2009). Productivity levels are low and grain yields oscillate typically around 1 ton per hectare. There is an important yield gap between experimental results and farmers’ reality (Rockström et al., in press). The key to closing the gap lies in improved water management. African countries on average only store 4% of annual flow (WWDR3, 2009), and a low water buffer means high vulnerability to both droughts and floods. Risk of climatic anomalies in Africa will even increase as a result of climate change (Conway, 2009). By 2020, 75-250 million people may be exposed to increased water stress due to the combined effects of climate change and increased demand(IPCC, 2008).

Project Challenges

Two key challenges concerning agriculture converge: how will Africa feed its growing population? And how will African agriculture cope with climate change? These challenges are recognized by Africa’s Leaders, and overcoming them is the key to food security. The Africa Water Vision calls for investment in water resources management. The Comprehensive Africa Agriculture Development Programme (CAADP, and the Alliance for a Green Revolution in Africa ( call for a boost in agricultural productivity. The CAADP’s first pillar rests on improvements in land and water management. The scope for a boost in agricultural productivity is greatest in rainfed agriculture: a recent extensive review of opportunities shows that yield improvements of rainfed crops of about 100% can be attained, against 10% for irrigated crops (Pretty and Hine, 2001). Food security would improve as a result of increased productivity of rainfed agriculture, but will especially benefit from increased resilience brought about by improved buffering of water.

In addition to the agricultural challenges, a third key challenge is: how to improve water security of rural Africans? Less than half of rural Africans currently have access to secure water (e.g. improved boreholes, wells or treated surface water) (MacDonald et al., 2009). Yet, the wider socio-economic benefits of safe water and adequate sanitation (improved health, livelihood security and poverty reduction) have been estimated at US$3-4 per US$ invested, with the highest returns in Africa (WHO, 2004). Again, buffering of water resources is the answer to the challenge.

Questions that Remain

Water harvesting (WH) presents highly adapted, flexible, easy to understand and implement, low-cost solutions to the productivity, climate adaptation and water security challenges, primarily by building water buffering capacity. WH technologies include centuries-old systems developed by local knowledge but also innovative new approaches. Together, these approaches hold great potential to boost economic development and sustain livelihoods in rainfed Africa. However, to unlock this potential, and despite the fact that WH has over the years received substantial interest from the research community, there is still considerable need for further advancement of knowledge:

  • Although the validity of the WH concept has proven itself time and again, WH technologies have so far remained local solutions. Recent success-stories in scaling of WH, like the Green Water Credits mechanism (Dent and Kaufmann, 2007), have triggered the question what is the potential of WH for Africa?
  • How to select appropriate technologies for areas with potential for WH development?
  • As WH technologies have mostly been studied only in the areas where they were originally developed, can they be adapted to different environmental and socio-economic conditions, and what would – under those circumstances – be their effectiveness? More in general, how does development of WH influence the provision of environmental services?
  • Is there an economic limit to scaling WH technologies in a catchment (Ngigi, 2003)?
  • Although socio-economic and political conditions necessary for WH are qualitatively known, no quantification has been made yet to understand and support individual decisions by farmers (Vohland and Barry, 2009). Furthermore, those factors have not been combined with biophysical factors in models to evaluate feasibility of WH technologies.
  • Whereas it is generally accepted that WH technologies improve water buffering and consequently reduce vulnerability to climate anomalies (it is their raison d’être after all), little is known about their economic viability under climate change scenarios.
  • What strategy should be taken to aid learning and action related to WH technologies and to disseminate successful innovations?

Contribution of WAHARA and Emphasis

WAHARA will contribute to closing these knowledge gaps, as it will study local WH solutions in 4 study sites throughout Africa from a transdisciplinary perspective that takes into account not only bio-physical aspects, but also socio-economic aspects and political conditions. The project will work closely together with stakeholders, to make sure that selected solutions are really meeting their needs. The effectiveness of WH technologies will be assessed under different environmental and socio-economic conditions, and will be modelled for various scenarios, considering drivers such as population growth, urbanisation and climate change. By combining results from the 4 sites, the potential of WH for the whole of Africa will be assessed.

The project addresses the call ENV.2010.3.1.1-4 Water harvesting technologies in Africa, with the purpose to contribute to ensuring food and water security in rainfedAfrica. It will do so by:

  • Main objective: Develop innovative appropriate WH technologies for different geographical regions of rainfedAfrica;
  • Emphasis 1 on WH technology design: Design WH technologies that have synergies with existing rainfed farming systems (i.e. that are sustainable); at least 10 designs of WH technologies adapted to local conditions will be tested.
  • Emphasis 2 on WH technology impact: Assess at catchment scale the on-site and downstream impact (environmental services) of WH technologies; impact assessments will be prepared for 4 catchments, and for different scenarios of drivers of change.
  • Emphasis 3 on WH technology integration: Develop criteria for sustainable impact on improving livelihoods with WH technologies under various pressures, considering economic development;guidelines for adapting WH technologies across rainfed Africa will be presented for at least 10 WH technologies, considering financial and economic cost effectiveness.
  • Emphasis 4 on WH technology learning and action: Develop guidelines to facilitate stakeholder learning and action about WH technologies in different (biophysical and socioeconomic) conditions; dissemination products targeted to stakeholders from local to international level will be developed and distributed, and guidelines to enable learning and action on WH will be prepared for third-party follow-up initiatives.

The project aims to develop solutions applicable beyond local study sites and indeed across the continent. In order to reach this objective, study sites are selected that are representative for rainfed Africa: Tunisia in the North, Burkina Faso in the West, Zambia in the South and Ethiopia in the East. Apart from the geographical spreading, a wide range of environmental and socio-economic conditions is also covered by these sites (as shown in Table 1.1 at country level).

Four different rainfall regimes: North, East, South and West

The 4 African partner countries represent different rainfall conditions: seasonally humid in Ethiopia, sub-humid in Zambia, semi-arid in Burkina Faso and arid in Tunisia. In all 4 countries, rainfall is seasonal, especially in Burkina Faso and Zambia, resulting in seasonal drought. Whereas the rainy season in Burkina Faso falls in the hot summer period, the scarce rains in Tunisia fall mostly in the cool winter period. The study sites are located in rural areas within these countries, which still rely heavily on agriculture.  In the poor developing countries Burkina Faso and Ethiopia more than 80 % of the population is still rural (Table 1.1); in Zambia this figure is slightly lower at 64%, whereas in Tunisia this has now declined to 34 %. The agricultural sector in these countries is withdrawing by far the largest amount of water, with 94, 86, 82 and 76 % of total water withdrawal in Ethiopia, Burkina Faso, Tunisia and Zambia respectively.

In 2001 the total amount of internal renewable water resources were 1668, 987 and 429 m3 per capita in Ethiopia, Burkina Faso and Tunisia respectively, the freshwater withdrawal of which was 6.4, 4.6 and 61 %. Zambia has internal renewable water resources above the world average of 7000 m3 per capita, of which the freshwater withdrawal rate is only 1.7%. However, the climate in Zambia is highly seasonal, resulting in seasonal shortages of water. Tunisia makes very good use of its scarce water resources as is evident from the area equipped for irrigation as % of irrigation potential, which is 70% against 11-16% for the other three countries.



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