Dams and reservoirs are essential to meet growing water and energy demands. While dams cumulatively impact downstream rivers and livelihoods on network-scales, dam development is mostly based on ad-hoc economic and environmental assessments of single dams. Here, we provide evidence that replacing this ad-hoc approach with strategic planning of dam portfolios can greatly reduce conflicts between hydropower and environmental objectives. In the Mekong Basin (800,000km2), 123 major dam sites (56 built and under construction) could generate 280,000 GWh/yr of hydropower. Cumulatively, dams risk interrupting the basin’s sediment dynamics with severe impacts on livelihoods and eco-systems. To evaluate cumulative impacts and benefits of the current portfolio (dams built and under construction), we combine the CASCADE sediment connectivity model with data on hydropower production and sediment trapping at each dam site. We then couple CASCADE to a multi-objective genetic algorithm (BORG) to a) identify dam portfolios resulting in an optimal trade-off between cumulative sediment trapping and hydropower production and b) an optimal dam development sequence for each optimal portfolios. We perform this analysis for a pristine basin, as well as starting from the current dam portfolio, deriving policy recommendations for which dams should be prioritized in the near future. The current portfolio creates a sub-optimal trade-off between hydropower and sediment trapping, exploiting 50 % of the basins total hydro-electric potential and trapping 60 % of the basin’s sediment load. Alternative portfolios could have provided the same hydropower for 30 % sediment trapping. Imminent development of mega-dams in the lower basin will increase hydropower production by 20 % but increase sediment trapping to >90 %. In contrast, there is still the opportunity to increase production by 30 % with only limited additional sediment trapping by prioritizing dam sites in upper parts of the catchment. Our findings argue for reconsideration of some imminent dam developments in the Mekong. With nearly 3000 dam sites awaiting development in the world’s large rivers, results from the Mekong are also of global importance, demonstrating that strategic planning and sequencing of dams is instrumental for developing more sustainable hydropower.
Lost opportunities and future avenues to reconcile hydropower and sediment transport in the Mekong Basin through optimal sequencing of dam portfolios
R. Schmitt;S. Bizzi;A. Castelletti;
2017-01-01
Abstract
Dams and reservoirs are essential to meet growing water and energy demands. While dams cumulatively impact downstream rivers and livelihoods on network-scales, dam development is mostly based on ad-hoc economic and environmental assessments of single dams. Here, we provide evidence that replacing this ad-hoc approach with strategic planning of dam portfolios can greatly reduce conflicts between hydropower and environmental objectives. In the Mekong Basin (800,000km2), 123 major dam sites (56 built and under construction) could generate 280,000 GWh/yr of hydropower. Cumulatively, dams risk interrupting the basin’s sediment dynamics with severe impacts on livelihoods and eco-systems. To evaluate cumulative impacts and benefits of the current portfolio (dams built and under construction), we combine the CASCADE sediment connectivity model with data on hydropower production and sediment trapping at each dam site. We then couple CASCADE to a multi-objective genetic algorithm (BORG) to a) identify dam portfolios resulting in an optimal trade-off between cumulative sediment trapping and hydropower production and b) an optimal dam development sequence for each optimal portfolios. We perform this analysis for a pristine basin, as well as starting from the current dam portfolio, deriving policy recommendations for which dams should be prioritized in the near future. The current portfolio creates a sub-optimal trade-off between hydropower and sediment trapping, exploiting 50 % of the basins total hydro-electric potential and trapping 60 % of the basin’s sediment load. Alternative portfolios could have provided the same hydropower for 30 % sediment trapping. Imminent development of mega-dams in the lower basin will increase hydropower production by 20 % but increase sediment trapping to >90 %. In contrast, there is still the opportunity to increase production by 30 % with only limited additional sediment trapping by prioritizing dam sites in upper parts of the catchment. Our findings argue for reconsideration of some imminent dam developments in the Mekong. With nearly 3000 dam sites awaiting development in the world’s large rivers, results from the Mekong are also of global importance, demonstrating that strategic planning and sequencing of dams is instrumental for developing more sustainable hydropower.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
