Green water and African sustainability

Sub-Saharan Africa faces an enormous challenge in meeting the basic needs of a population that will nearly triple between now and the end of the twenty-first century. Managing water effectively, sustainably, and equitably will be a critical component for meeting this challenge, especially in the context of the Sustainable Development Goals (SDGs). We focus on green water (i.e. the water that comprises evaporation and precipitation flows), rather than blue water (i.e. the liquid water flowing in rivers, lakes, and aquifers), since green water is primarily used for food production. We examine three key insights into green water management at their relevant spatial and temporal scales: farm-based food production using the vapor shift (annual, local); landscape and ecosystem interventions (multi-year, national/regional), and moisture recycling (decadal, regional/continental). As such, these insights are organized into a spatial and temporal framework, which helps to clarify how feedbacks within and among these different scales create opportunities for intervention. Our key finding is that green water management at the landscape-scale constitutes the best entry point for providing leverage at both smaller and larger scales, in terms of time, space, and policy. We conclude by highlighting the urgent need for much more resilient, cross-scale green water systems that can accommodate the impending, nonstationary changes related to climate change. This urgency is further underlined by the very short time horizon for achieving the SDGs by 2030.