A modelling strategy to design hedgerow barrier systems for water conservation in the Sahel

Heterogeneity in space and time makes it difficult to evaluate the hydrologic effects of hedgerows in between crops. In this study a robust modelling system for designing hedgerow barrier systems is introduced. The system is demonstrated with experimental data over three years from a site in central Burkina Faso. Soils at the site are prone to crusting and consist of a sandy loam in the top layer and clay in deeper layers. Measurements comprise runoff from differently sized plots (1, 5 and 10 square meters), water storage into the soil, and rainfall. It appears that the relevant hydrologic processes can be represented with the available measurements by two compact dynamic models, each comprising two states (runoff and soil water; water use and soil water), one input (rain; potential evapotranspiration) and two spatial units (hedgerow and cropped area). The analysis of the phase planes of the models reveals which combinations of alley length and hedgerow type lead to desirable combinations of both runoff and evapotranspiration. This information can be interpreted directly in a qualitative sense or alternatively used for a Monte-Carlo analysis of the system