Evaluating the Impact of Rainwater Harvesting Technology at Scale

In Niger, 250,000 hectares of land are lost every year to desertification. This drastic loss of productive land harms smallholder farmers who depend on fertile soil for food and livelihoods.

To help restore the degraded soil, researchers are testing a rainwater harvesting method built around two catchment techniques that collect both rainfall and runoff while increasing the nutrient content of the soil: demi-lunes (half-moons) and zai (soil pits).

After a simple training, farmers are able to construct the catchments themselves using a pickaxe and a shovel, which they likely already own.

The team previously conducted a randomized controlled trial (RCT) to evaluate approaches to trainings on demi-lune construction and found that the trainings increased adoption of the technique from 4 percent in the control group to 95 percent in the training group in the first year and resulted in a meaningful (0.15 standard deviation) increase in agricultural production over three years.

However, few smallholder farmers know how to construct demi-lunes and zais.

Building upon the results of the previous, the researchers are conducting a new RCT in partnership with the Government of Niger and Sahel Consulting Group to: (1) optimize the rainwater harvesting training program so that it can be administered sustainably by the government and other partners in Niger and (2) evaluate the effectiveness of the program at scale.

In addition, the research will compare the costs and benefits of in-person monitoring with remote sensing techniques.

Results from these studies will inform the Government of Nigers efforts to promote rainwater harvesting as a defense against desertification as it aims to preserve the livelihoods of millions of smallholder farmers.