Informing regional water-energy-food nexus with system analysis and interactive visualization – A case study in the Great Ruaha River of Tanzania

In sub-Saharan Africa, water resources are scarce and subject to competing uses – especially for agricultural production, energy generation, and ecosystem services. These water intensive activities in the Usangu plains and the Ruaha National Park in southern Tanzania, present a typical case for such water competition at the water-energy-food nexus. To decipher the coupled human-nature interactions in the Great Ruaha River basin and effectively communicate the results to non-technical practitioners, the water-energy-food nexus competition in the system is simulated using an advanced water system modeling approach and findings are visualized via interactive web-based tools (Data-Driven Document, D3) that foster fuller understanding of the findings for both practitioners and stakeholders. Our results indicate that a combination of infrastructural and procedural measures, each acceptable from a social and economic perspective, and understanding that zero flows cannot be totally eliminated during dry years in the Ruaha National Park, are likely to be the best way forward. This study also reveals that the combination of improvements in irrigation efficiency, cutbacks on proposed expansion of irrigated lands, and a low head weir at the wetland outlet, significantly reduces the number of zero flow days (i.e., increasing ecosystem function), resulting in positive effects on agricultural sector from limited (if any) reduction in rice crop yields. These upstream measures are all relatively cost efficient and can combine to free-up resources for other economic activity downstream (i.e. more stable hydropower production).