Ecological pressure index

The health of a river ecosystem affected by human activities is measured through EPI, which was evaluated as

where FI, WDI, FIS, FDI, FRI, and PNF are the fragmentation index, wetland dis-connectivity index, fraction of impervious surfaces, flow disruption index, fish richness index, and proportion of non-native fish; FI₀, WDI₀, FIS₀, FDI₀, FRI₀, and PNF₀ are threshold values of the foregoing indicators when ER approaching 80%. It should be noted that FI is calculated using Eq. (¹⁰), noting that not all dams are built for navigability purposes,

where α is a proportionality factor determined from

in which N_navi is the number of dams used for navigability in a basin, and N_total is the total number of dams in a basin. FI’, WDI, FIS, and FDI data were extracted from http://www.riverthreat.net/data.html. N_navi, and N_total were obtained from Global Reservoir and Dam (GRanD) Database (http://globaldamwatch.org/grand/). Data on the total number of freshwater fish species living in the river basin and the number of non-native fish species were obtained from the Fish-SPRICH database (https://static-content.springer.com/esm/art%3A10.1007%2Fs10750-012-1242-6/MediaObjects/10750_2012_1242_MOESM2_ESM.txt).

Supplementary Table ⁵ lists the EPI for each GIW in 2015.