IMIXSED · Integrating isotopic techniques with Bayesian modelling for improved assessment and management of global sedimentation problems

Integrating isotopic techniques with Bayesian modelling for improved assessment and management of global sedimentation problems

Siltation presents a credible threat to river basin ecosystem service provision and water security. River silt originates, however, on catchment hillslopes and the primary driver for mobilisation and translocation downstream is soil erosion on agricultural land where loss of this finite resource threatens food security. Knowledge of sediment source and transfer dynamics in river catchments is critical to inform management policy decisions to maintain and enhance future food and water security. Identification of the source and behaviour of different types of sediment is critical if we are to design effective management plans. Cutting edge nuclear techniques have been developed to trace river silt back to source, in a jointly Coordinated Research Programme between the UN Food and Agriculture Organisation and the International Atomic Energy Agency. However, these new techniques have led to a step change in data complexity. While these datasets capture real world complexity in time and space, the conventional statistical approaches to quantify sediment provenance do not. This severely limits the power of the new tracing techniques. Advances in ecological source models based on Bayesian statistics, however, offer a solution. New models e.g. MixSIAR have been developed that can deal with the complexity in a quantitative way and, if tailored to specific river basin sediment data, will allow us to address the above challenge. Research and Innovation Objectives: 1. To marry together the strengths of isotopic and biogeochemical sediment tracer technology in the EU with new developments in ecological source apportionment models led by US scientists to deliver a powerful sediment source apportionment toolkit to combat threats to global food and water security from soil erosion and siltation. 2. To demonstrate the capability of the integrated IMIXSED approach to deliver EU development policy goals in two demonstration catchments (Gilgel Gibe in Ethiopia and Manyara in Tanzania) where food, water and energy security is threatened by siltation of hydropower reservoirs. The new IMIXSED approach to sediment tracing and apportionment of problem sediment in complex river basins offers better system representation by accounting for source contributions weighted by tributary. The step change proposed by IMIXSED in structuring data according to geographical catchment hierarchy leads to a more representative unmixing model structure. The approach offers a more accurate means of estimating the contribution of primary sediment sources linked to land use where more than one sub-catchment feeds a sediment problem downstream. The new tool for source apportionment in river basins offers wider application in systems affected by natural and human-induced change and the lessons learned are relevant to source apportionment applications across the world. The new data handling routines developed in IMIXSED support management of complex source apportionment challenges to help us tackle the global challenge of improved food, water and energy security through mitigation of soil erosion.

Data: CORDIS, © European Union