A global challenge
Figure 3: The current dam portfolio in the 3S consists of 21 dams built or under construction and 21 more at various planning stages (a). We used cascade to evaluate increasing cumulative sediment trapping over the construction of the planned dam portfolio (Figure 3 b, square markers) in order to quantify trade-offs between increasing hydropower production and increased sediment trapping. We also analyzed 17,000 alternative dam portfolios, and identified optimal trade-offs between sediment trapping and power production. A key finding is that there would have been dam portfolios with higher power production but lower sediment trapping (see arrow, and small network plots c and d), hence with lower environmental impacts and sedimentation in reservoirs, but higher economic benefits. C shows the current dam portfolio, d shows the alternative optimal dam portfolio.