We demonstrated the capability of the integrated IMIXSED approach to deliver EU development policy goals in three demonstration catchments (Gilgel Gibe in Ethiopia, Manyara in Tanzania and Upper Chitlang in Nepal) where food, water and energy security is threatened by siltation of hydropower reservoirs. In the Ethiopian example, IMIXSED methodologies were applied in the catchment of the Gilgel Gibe hydroelectric dam, one of a series of development projects launched by the Federal Government of Ethiopia. The Gilgel Gibe reservoir is silting up and it has been proposed that landslides in the upper catchment may be an important sediment source. From a management perspective, the understanding of nature and relative importance of the principle sediment sources within a catchment is needed to support the design and implementation of sediment control strategies in catchments. The IMIXSED approach was applied in the Unta sub catchment using XRF geochemistry. Source discrimination indicated relative differences between the broad source groups but the main groupings separated surface and subsurface derived material. The mean contributions from individual source types (i.e. cultivated land, grass land, landslide, homestead and wood land) varied but landslides remained the dominant source to stream sediment because of their proximity to river (highly connected to river) and high abundance in the Unta catchment. To support land remediation and management change, further targeted research is now needed to develop knowledge of landslide processes and drivers in the landscape and the catchment-wide contribution of landslides to sediment delivery into the Gigel Gibe reservoir. In the Tanzanian example, work was based in the Lake Manyara basin in northern Tanzania, working in a subcatchment of the Makauni river catchment. Land use is mixed with widespread savannah grazing lands and agricultural land for crops. Sever gully erosion is observed in the grasslands. This part of the world is at risk of changing rainfall and runoff patterns with climate change and we hypothesised that land management factors will amplify the impacts of extreme rainfall events. Sedimentation threatens downstream ecosystem services in the Lake Manyara Man and biosphere UNESCO reserve. Research and stakeholder questions relate to erosion process and management solutions and we applied the IMIXSED approach to develop knowledge of sediment sources in different geomorphic zones of the study catchment. Sources were rationalised down to four groups: UPPER CATCHMENT forested, MIDDLE catchment surface and subsurface soil, LOWER catchment soil (undifferentiated between surface and subsurface since the soils here represent ‘recent’ reworked valley fill material). Results from the model indicated that while there is extensive visible gullying in mid catchment, surface erosion fed by sheet wash into existing gullies remains a key input. Fingerprinting reveals importance of sheet erosion on steeper land.
