Assessing River Basin Development Given Water‐Energy‐Food‐Environment Interdependencies. Issue 8 (7th August 2020) - Geressu, Robel
Abstract: Many river basins in the Global South are undergoing rapid development with major implications for the interdependent water‐energy‐food‐environmental (WEFE) "nexus" sectors. A range of views on the extent to which such natural‐human systems should be developed typically exists. The perceived best investments in river basins depend on how one frames the planning problem. Therefore, we propose an approach where the best possible (optimized) implementations of different river basin development scenarios are assessed by comparing their WEFE sector trade‐offs. We apply the approach to Tanzania's Rufiji river basin, an area with multiple WEFE interdependencies and high development potential (irrigation and hydropower) and ecosystem services. Performance indicators are identified through stakeholder consultation and describe WEFE sector response under scenarios of river basin development. Results show considerable potential exists for energy and irrigation expansion. Designs that prioritize energy production adversely affect environmental performance; however, part of the negative impacts can be minimized through release rules designed to replicate the natural variability of flow. The reliability of monthly energy generation is more sensitive to environmental‐oriented management than the cumulative annual energy production. Overall results highlight how sectoral trade‐offs change depending on the extent of development, something that may be difficult to regulate in the future, and that there are important basin‐scale interdependencies. Benefits and limitations of the approach and its application are discussed. Plain Language Summary: Infrastructure in water‐energy‐food‐environment systems such as dams can play a beneficial role in supporting hydropower production and regulating the variability of river flow. However, these benefits often come with negative environmental impacts on wildlife, affect income from other economic sectors, and can damage river‐linked ecosystems (e.g., wetlands, floodplains, riverine forests, and mangroves). System‐scale option assessment approaches that consider the different relevant issues simultaneously help identify infrastructure and operating policy designs with acceptable balances of potential benefits and impacts. While optimized model‐based assessments can balance outcomes across performance metrics, this is contingent on the need for effective coordination between sectors and between upstream‐downstream developments. One way to help design future systems is to compare the energy, agricultural, and environmental conservation trade‐offs implied by different extents of development (i.e., realization of various reservoirs and irrigation schemes). We apply such a multisector spatial computer‐aided design approach to the Rufiji river basin in Tanzania and consider linkages across the water‐energy‐food‐environment sectors. Results show considerable potential for infrastructure development in the basin but highlight important trade‐offs between the sectors, particularly how downstream performance indicators are affected by upstream cumulative effects of informal irrigation expansion, something that may be difficult to regulate in the future. Key Points: System wide multi‐sector assessments reveal the benefits of coordinated interventions and help identify sectoral trade‐offs Trade‐offs between water, energy, food and environment can be optimised under different scenarios of river basin development Multi‐criteria decision‐making methods can inform collaborative water‐energy‐food‐environment system planning in Tanzania