Session FT 4.41
Green and blue water productivity
Stockholm International Water Institute
Stockholm Environment Institute
International Water Management Institute
International Food Policy Research Institute
Association for Strengthening Agricultural Research in Eastern and Central Africa
The World Conservation Union
The objective of this session is to increase the understanding of the role of blue and green water flows in poverty reduction and ecosystem sustainability. Whereas one-third of the precipitation feeds rivers, lakes and aquifers, two-thirds take the green water path, i.e. generates water in the soil consumed in plant production and returns to atmosphere as evapo-transpiration from the landscape. With regard to livelihood support and environmental stability, it is crucial to recognise this significant component of the water cycle. One of the greatest challenges in water resources management – and in programs aiming at improved livelihoods – is to effectively utilise this green water flow. By integrating land and rainwater resources management, the fraction of the rains that is potentially available as soil moisture – the green water resource – can be enhanced and, thus, the unproductive evaporation from moist surfaces minimised. By linking land and water resources, a much more functional approach to water resources management will be achieved since land characteristics, to a large extent, determine the flows of water in the landscape. A related objective is to emphasise that there is a significant potential to increase food production if a more realistic water perspective is permeating policy, extension services and development initiatives.
In savannah zone climates, dryspells are the most limiting factor, but can be met by occasional supplementary irrigation, relying on locally recharged groundwater or rainwater harvested in farm ponds. Since large productivity gains have been shown possible and the method shown to work for smallholder farmers, it would, if upscaled, open for agricultural development also in upstream regions. The next step is therefore to analyse the implications of a desirable basin scale upscaling for downstream blue water flow and aquatic ecosystems. Since green water phenomena have been shown to be closely linked to land use and terrestrial ecosystems, an integrated approach will have to be developed to land use/water/ecosystems, turning IWRM into ILWRM, where L stands for land use.
The green-blue approach is particularly useful by its close link to livelihood development in poor and hunger-prone semi-arid regions. The link that it constitutes between land use, groundwater recharge and streamflow generation means that green water will urgently have to be entered into water policies and governance models. Through the seminar, the multi-party Green and Blue Initiative proposal, to be launched at the World Water Week in Stockholm in August 2006, received international exposure, inviting other interested parties to join. The project involves i.a. local scale green-water based livelihood development, upscaling efforts and governance development in a set of pilot basins.
Orientations for action
- Find out the conditions for widespread take up of the proven green water based livelihood development on smallholder farms, analysing possible social and cultural restrictions that tend to hinder upscaling, and potential blue water consequences downstream of such upscaling.
- Secure that land use be properly integrated into IWRM in view of the fundamental relevance of consumptive green water use for runoff generation and groundwater recharge (land use as a streamflow impacting activity). The goal is to is to find an acceptable balance within a catchment between (i) rainfed and irrigated agriculture and (ii) terrestrial and aquatic ecosystems that maximizes the benefits brought by water and ecosystems (in a sustainable way) and distributes them in an equitable manner between its inhabitants.
- Enter green water into both water governance and water resources education.
Local Actions presented
Sustainable Livelihoods and green-blue water management through conservation agriculture in East Africa
Patrick Fox, Red Cross International
Dry spells seriously affect rain fed yields and impact on farmers risk perceptions. Statistically dry spells occur each rainy season, causing serious yield loss. At the same time only less than 10 % of the rainfall is used productively, i.e., large volume of water is lost to the farmer as runoff. Storage systems for supplemental irrigation are tested to bridge dry spells and upgrade the system. Normally ditch systems in semi-arid Africa are not used for gravity fed irrigation of smallholder crops – here this is tested by locating small micro-dams in upstream locations.