Rain is causing many of the problems of land degradation and desertification, but rain can also be the solution to the same problems. As you probably have discovered in the How we do it section, we work with a unique approach: ‘Hydrologic corridor’. The technique behind our approach is explained here.    

In our project areas there is still often enough rainfall, but the rain is coming down in very short periods with high intensities, causing these problems. The bare soils can’t sustain these heavy rains and the rainwater is flowing away as surface runoff. This causes erosion, loss of fertile soils and downstream flooding. The majority of the rainwater is flowing away and ends up unutilized in the saline ocean.

SevereErosion

Severe erosion at Tsavo riverbank due to river flooding and excess run-off

Using simple rainwater harvesting techniques we can alter the land to retain more water and allow this water to infiltrate. This is where the shovel comes in! There are many different rainwater harvesting techniques. For example small trenches to capture the water, dams to retain runoff or agricultural methods to break open the hard soil allowing water to infiltrate.

Technique01

Manually created semi-circular bunds that capture water

Terrassen

An example of terraces to retain run-off. image © Hanspeter Liniger, Wocat

Depending on local conditions the most appropriate technique is selected. This is depending on soil conditions, slope, amount of rainfall and other physical properties of the area. But it also depends on the land use: an agricultural area requires different techniques then a pastoralist area. Based on our knowledge and experience of how these techniques are used throughout the world, we determine, together with our local partners, the most suitable techniques for our project areas.

These interventions allow more water to infiltrate in the soil. This allows vegetation to recover since there is more water available, especially in the dry season. More plants contribute to more biodiversity and the rehabilitation of an ecosystem. The increased vegetation cover also helps to further slowdown and retain rainwater and improve soil conditions. Bringing back the vegetation therefore results in a positive feedback loop.

The vegetation cover also increases the amount of evapotranspiration and thereby the moisture in the air. This causes local cooling and changes in air circulation.

vegetation-Change

The cooling effect of vegetation; shadow and lower temperatures. Image © Michal Kravčík

All these processes (more moisture, cooling and changes in air circulation) can increase local cloud formation and rainfall. This again is a positive feedback loop: if the rainy seasons starts a little earlier, or lasts a bit longer this has a positive effect on vegetation resulting in even more gradual spread rain, and so on.

What makes our projects unique is their scale. Since we work in large areas (projects of 20 km² = 2,000 hectares ≈ 3 times Amsterdam city center) these processes occur on a large scale and our interventions also impact areas outside of the project areas. We don’t work in just one project area, but select 15 project areas. The restored microclimates in these project areas interact to form a Hydrologic Corridor, creating atmospheric cooling in an area of 20,000 km². So these climate effects influence large regions.

A more elaborate explanation of these processes is described in our scientific whitepaper, including a list of all scientific papers and reports on which this is based.

How do we measure our impact? 

We invest substantially in scientific research and monitoring. We work together with Wageningen University to select Hydrologic corridors and suitable project locations through computed climate modelling.

To monitor and document the recovery and stabilization of the ecosystem characteristics we have a monitoring framework in place that we use for both baseline, impact monitoring and evaluation. This framework is related to existing and accepted international ecosystem services valuation frameworks such as Millennium Ecosystem Assessment (MA), The Economics of Ecosystems and Diversity (TEEB), REDD+, etc. By adopting several standards we can report our return on investment based on different parameters. Some of which are quantitative and some are monetized to ensure continuity of our projects.

See our monitoring framework for more details on valuing ecosystem services.