The International Water Management Institute (IWMI) together with FutureWater and other partners have published a report that presents findings from a study conducted to explore the synergies and trade-offs between built (i.e., engineered) and natural (i.e., ecological systems) infrastructure in the Tana River Basin, Kenya. The study considered hydrological, ecological and economic processes in order to value flow-related ecosystem services. It provides quantitative insights into the links between flow and the benefits derived from both built and natural infrastructure. The results provide initial perspectives not just on the monetary values of a number of ecosystem services (and how they change as flows vary and are altered by large dams) but also, importantly, aspects of equity and social inclusion, that also need to be considered in decision-making.
For this study, FutureWater focused on the Thika/Chania watershed, containing the important Mwagu intake for Nairobi Water Supply. The previously built SWAT model for this area was used to assess the impact of land management interventions under six different climate scenarios. Streamflow dynamics, sediment concentration at specific points of interest and total sediment loads in the watershed were assessed to evaluate the sustainability of land and water management, by taking business-as-usual practices as a reference. Next to baseline conditions, the study focused on three future periods: foreseeable future: (2030s), long-term future: (2050s), and far horizon (2080s).