Input data set: Reservoirs and dams (Group III)

Future dam locations are based on the methodology of Gernaat et al. (2017), which identifies sites suitable for hydroelectric power plants at near-global coverage. Here we apply the methodology for multiple combinations of GCMs and global hydrological models (GHMs). We further combine it with projections for future hydropower usage from integrated assessment models (IAM), i.e. taking into account the projected expansion of hydropower caused by rising energy demands and/or climate change mitigation.
Briefly, run-off simulated by WaterGap2-2c (Müller Schmied et al., 2016, 2021) at 0.5° x 0.5° resolution is downscaled based on high-resolution topographic data, yielding 15’’ x 15’’ discharge data. Exploring a large number of potential sites (every 25 km along every river), the optimal type (river vs. diversion canal power plant) and dimensions of a hydropower plant at a given site are identified using an optimization approach, aiming for lowest-cost electricity generation. We rank potential locations by their electricity production costs, leading to a cost-supply curve for the expansion of hydroelectric power supply. Given the extension of hydropower capacity projected in an IAM (REMIND, https://rse.pik-potsdam.de/doc/remind/2.1.0/) analysis of the respective scenario, we populate potential dam location sites (starting from the site with cheapest electricity generation) until the projected generation capacity for a given year is reached. This is repeated for each time step of the hydropower demand scenario (i.e. every 5 or 10 years).

In the corrected version released in May 2026, potential dam locations with unrealistically large reservoir volumes were excluded as unrealistic. To address potentially unconstrained dam construction in remote areas, a cost-of-electricity (COE) cutoff at 10 ct/kWh was applied, assuming dams with electricity costs above this value are unlikely to be built. In addition, potential dam locations with defined reservoir volumes larger than 300 km3 (3 x 10^11 m3) were removed. The dam scenarios were then recalculated by mapping the remaining potential dam locations to the REMIND hydropower demand projections. The corrected files replace the previous version (a further correction is pending as of August 2026, see Caveats).

For each future scenario, candidate hydropower sites, plant design, cost of electricity, and the resulting cost-ranked supply curve are computed once from a single representative discharge climatology, rather than being recalculated at every REMIND time step. Only the regional hydropower capacity target (from REMIND, by SSP and time step) and the resulting construction years of newly built dams vary between time steps, the underlying site assessment does not.

The discharge climatology used for this assessment differs between the two scenario families:
- noadapt scenarios (ssp126soc-noadapt, ssp370soc-noadapt, ssp585soc-noadapt) use observation-based climate forcing (obsclim), with candidate sites assessed against discharge from 1991–2020.
- adapt scenarios (ssp126soc-adapt, ssp370soc-adapt, ssp585soc-adapt) use GCM-based climate forcing, bias-adjusted future climate from each of the five CMIP6 GCMs, with candidate sites assessed against discharge from 2071–2100, representative of end-of-century conditions under that GCM/SSP combination.

Most scenario files are driven by WaterGAP2-2e discharge. For one noadapt and one adapt scenario, an additional H08-driven file is provided so users can gauge the dataset's sensitivity to the choice of hydrological model.

- May 2026: applied a 10 ¢/kWh cost-of-electricity cutoff and excluded reservoirs > 300 km³ — see Specification for details. Users who downloaded files before this date should re-download.

- May 2026: removed historical-climate discharge files (GCM-based, 1985–2014) that had been included in the -adapt folders in error; filenames simplified.

- August 2026: an inconsistency in the IAM-specific region mapping was discovered, which could cause some dams to be built more than once under different regions. All ssp126soc/ssp370soc/ssp585soc scenario files (adapt and noadapt) have been withdrawn pending a fix. See data.isimip.org/issues/94 for status; corrected files will be republished here.