Land use change often results in degradation of soil and water resources at the river basin scale. While traditional systems were adapted to local variations in soil properties and topography, modern systems of intensive agriculture do not take these local variations into account and even severely modify soil properties. Our research focuses on i) the impact of local variations in topography and soil properties on water availability in semi-arid regions and ii) the relation between soil properties and global change processes such as greenhouse gas emissions. This work is based on field experiments and monitoring as well as the analysis of existing data bases of land use and soil properties.