A blue water scarcity-based method for hydrologically sustainable agricultural expansion design
At the heart of the vision of sustainable development and intergenerational responsibility lies the prudent use of natural resources. Agriculture is a key sector both in terms of resources consumed and of goods and services provided. Recently Its intensification and expansion have been studied and their sustainability evaluated, often with a particular focus on water management. While, in literature, possible agricultural strategies have been based on local water availability and, in some cases, downstream effects of such strategies have been evaluated, a method to identify and quantify hydrologically sustainable land use and crop use changes directly accounting for downstream effects is yet to be defined. Here we propose a framework to assess hydrological sustainability of land use and crop use changes, preventing both in situ and downstream effects. We apply this framework on the case study of coffee plantations expansion in Kenya, a sector that is seeing, and is planned to see, a rapid growth, given its potential in promoting agricultural, economic, and social development, not without risks associated to hydroclimatic change. We simulate the hydrological alterations caused by coffee plantation expansion onto available suitable areas, and use these simulations to identify areas where the expansion does not generate water scarcity either in situ or downstream. The assessment of hydrological suitability proves effective in preventing water availability reduction. Areas selected for expansion present similar total water footprints as currently used areas, but with higher precipitation-generated water availability. The proposed methodology identifies and quantifies areas in a physically robust, and thus transparent, way, also maintaining flexibility to the selected expansion scenario and low data intensity. This makes this framework a potentially easily replicable methodology for planning sustainable agricultural development within planetary boundaries.