About GWC

The field water balance

Theory behind GWC

Run-off and high evaporation rates lead to the loss of green water, defined here as the water that is held in the soil (see image below). Soil and water conservation (SWC) measures such as mulching and contour cropping reduce the amount of run-off and evaporation. As a result, the amount of water available for plants and deep percolation to the groundwater (blue water) increases.

Besides runoff and high evaporation, erosion leads to increased sediment loads in rivers causing silting up of dams. There are many soil and water management practices available to diminish accelerated soil erosion and improve water quality.

River catchment areas that include metropolitan centres, such as Nairobi, Fes and Beijng, are increasingly experiencing both floods and droughts. Moreover, these catchments are threatened by recurrent water shortages and erosion, which causes dams to silt up. Farmers and citizens often blame climate change and erratic rainfall for their problems. But these catchment problems are also exacerbated by too much evaporation and excess runoff from upstream farmers’ rain-fed fields.

Payment in return for conservation practices

In 2005, the International Fund for Agricultural Development (IFAD) and ISRIC World Soil Information realized that a new type of investment mechanism was needed for these rain-fed farmers. Worldwide there are thousands of individual farmers already applying land and water conservation practices. This can be seen in the online database of WOCAT (World Overview of Conservation Approaches and Technologies) which lists more than 450 technologies and 250 approaches from over 50 countries. However, for impact to be achieved on the scale of an entire catchment area, large groups of rain-fed farmers have to participate. IFAD and ISRIC, initially with additional support from the Swiss Agency for Development and Cooperation (SDC) and FINNIDA, decided therefore to elaborate a Green Water Credits concept. This is a mechanism that provides compensation to communities in return for Green Water Management: water management by large groups of farmers so that both water quality and quantity increase.

Assessment studies

In 2007, the GWC team selected the Tana River basin in south east Kenya to demonstrate the principles of Green Water Management. The Tana River basin is characterized by severe floods and land degradation, rain-fed farmers upstream and relatively wealthy water users downstream. In addition, there were sufficient baseline data for scenario studies. Such studies, for example on the potential costs and benefits of water management by farmers, are needed to set up a programme and to convince stakeholders to participate. In 2009, the team selected a second catchment for a proof-of-concept assessment: the Sebou River basin in Morocco.

Fund and programme

In both Kenya and Morocco the scenario studies have shown that the benefits of Green Water Management far outstrip the costs and that a fund and programme for rain-fed farmers is feasible. In 2011, partly due to the outcomes of these scenario studies, international and Kenyan parties agreed to assist 400,000 smallholder farmers in the Tana River basin, using a new fund of US$ 40 million created by IFAD and Kenyan water and electricity companies. The goal of the GWC team now is to assist these Kenyan stakeholders, and also stakeholders in other catchments in the world that want to use the principles of Green Water Credits for improved land and water management.