Sediment Management for Reservoir Sustainability and Cost Implications Under Land Use/Land Cover Change Uncertainty

Addressing uncertainty in sediment predictions due to land use/land cover (LULC) change could better inform the selection of sediment management options for reservoir sustainability. We used the Nam Kong catchment of the Mekong River Basin in Southern Laos, with two hydropower dams in series, to understand the implications of LULC change uncertainty for catchment-level and reservoir-level sediment management options. The catchment-level sediment management options of terracing, vegetative filter strips, and no tillage were evaluated applying the Soil and Water Assessment Tool (SWAT). The reservoir-level sediment management option of flushing was assessed using the Sediment Simulation Screening Python Model (PySedSim). Costs of sediment management options were assessed via the economic value of the loss in hydropower production and the avoided cost of dredging. Our results suggest that LULC projections resulted in high variability in loss of reservoir capacity and cost of sediment management. Terracing was found to be the best catchment-level management option at decreasing both the magnitude and variability in loss of reservoir storage for both dams, but it was also the most expensive option. Flushing was also effective in reducing sedimentation, but it was less economically beneficial compared to catchment-level sediment management options. Combinations of catchment-level and reservoir-level management strategies, however, can be effective in reducing the magnitude and variability in loss of reservoir storage and associated costs in response to LULC change uncertainty.

Automated summary

The study indicates that uncertainty in land use/land cover change results in high variability in loss of reservoir capacity and sediment management costs. Terracing is the best catchment-level management option for reducing both the magnitude and variability in reservoir storage loss, although it is the most expensive option. Flushing is effective in reducing sedimentation, but less economically beneficial compared to catchment-level options. Combinations of catchment-level and reservoir-level management strategies can effectively reduce the loss of reservoir storage and costs associated with land use/land cover change uncertainty.