Projected future changes in water resources across all global land areas at 0.5° × 0.5° resolution, built on top of the ISIMIP3b protocol. It covers three hydrological variables — total runoff, diffuse groundwater recharge, and actual evapotranspiration — derived from a multi-model ensemble of global hydrological and CMIP6 climate models. Relative changes are provided for three future 30-year horizons under three emissions scenarios (SSP1-2.6, SSP3-7.0, SSP5-8.5), at annual and seasonal timescales. The ensemble spread captures projection uncertainty, supporting risk-aware climate change adaptation planning.
A multi-model ensemble dataset of projected future changes in water resources across all global land areas, from Earth Blox.
Climate projections of water availability are inherently uncertain: different global hydrological models (GHMs) respond differently to the same climate forcing, and different global climate models (GCMs) produce different forcings for the same emission scenario. Working with a multi-model ensemble — rather than a single model run — is therefore essential to characterise this uncertainty honestly and to support risk-aware adaptation decisions. By spanning 4 GHMs × 5 GCMs × 3 SSPs, the dataset exposed here samples the main axes of uncertainty and allows users to derive robust statistics (medians, percentiles, model agreement) rather than relying on a potentially unrepresentative single trajectory.
This document describes the structure of the derived Zarr store built from that archive and provides ready-to-run code snippets for common analysis patterns.
Store location: s3://us-west-2.opendata.source.coop/earthblox/cciwr/data/cciwr.zarr
The store contains three groups, each a separate N-dimensional array dataset:
Each group holds three hydrological variables:
Coordinate values
Storage layout (Zarr v3, sharded) — RC / FUTUR:
Requires Zarr v3 (zarr>=3) to read the sharded store.
Compute the 25th percentile, median, and 75th percentile of the relative change in
groundwater recharge (qr) across all GHM × GCM combinations at a single point of interest,
for a user-defined SSP, horizon, and season.
The POI is snapped to the nearest 0.5° grid cell automatically.

Compute the ensemble median (across all GHM × GCM combinations) of the relative change in
total runoff (qtot) over Europe, for a user-defined SSP, horizon, and season.
The map uses a diverging blue–white–red colormap centred on 0% to make drying vs. wetting signals immediately visible.

The ensemble median tells you the central signal, but not how confident the models are. A more decision-relevant question is: for a given level of stress, how many of the ensemble members agree that it will be reached?
Here we map model consensus over Europe — the percentage of the GHM × GCM members
that project a relative change in groundwater recharge (qr) below a chosen drying
threshold. The threshold is set with the THRESHOLD parameter at the top of the next cell
(default: −20%). A value of 100% means every model agrees the cell dries by at least
that much; 0% means no model does. Note that the number of available members can vary from
pixel to pixel, so the consensus is normalised by the valid members at each cell rather than
a fixed count. This turns the raw ensemble into a transparent, risk-oriented agreement map,
using a sequential colormap where darker = stronger consensus on drying.

This composite dataset is derived entirely from the ISIMIP3b (Inter-Sectoral Impact Model
Intercomparison Project, phase 3b) global water-sector simulation archive. Monthly time series
of total runoff (qtot), diffuse groundwater recharge (qr / qrd), and actual
evapotranspiration (evap-total) were downloaded from the ISIMIP data repository
(https://data.isimip.org/) under the 2015soc experiment
(protocol). The historical reference
period uses the historical_histsoc_default specifier; future projections use the
ssp126_2015soc-from-histsoc_default, ssp370_2015soc-from-histsoc_default, and
ssp585_2015soc-from-histsoc_default specifiers for SSP1-2.6, SSP3-7.0, and SSP5-8.5
respectively. The full simulation data are cited as:
Gosling, S. N., Müller Schmied, H., Bradley, A., Burek, P., Gedney, N., Grillakis, M., Guillaumot, L., Hanasaki, N., Ito, A., Kou-Giesbrecht, S., Koutroulis, A., Nishina, K., Otta, K., Sahu, R.-K., Satoh, Y., and Schewe, J. (2024).
ISIMIP3b Simulation Data from the Global Water Sector (v1.3).
ISIMIP Repository. DOI: 10.48364/ISIMIP.230418.3
Döll, P., Attard, G., Kneier, F., and Müller, L. (2026).
Supporting climate change adaptation worldwide: A web application for exploring uncertain future changes in water resources. EGUsphere [preprint], under review for Geoscience Communication.
DOI: 10.5194/egusphere-2026-1829
The CCIWR Explorer is a free Earth Engine web application that lets you visualise ensemble projections of total water resources, groundwater recharge, and evapotranspiration across four seasons and three SSP scenarios — including percentile boxes for individual 0.5° grid cells.https://ee-gwp.projects.earthengine.app/view/cciwr-explorer