The information provided on Water Security Compass beta includes outputs from the H08 model and their post-processing. Below is a technical description of this data.
Assessment of global water scarcity (Global viewer)
1. Model
The H08 model is one of the world's most advanced global water resource models, capable of calculating and estimating the main components of the natural water cycle as well as human water use and management. The information provided on Water Security Compass beta is based on the conditions described in Hanasaki et al. (2018) [1], which outlines the standard calculation of the H08 model, with the following modifications:
- Horizontal spatial resolution: 5 × 5 minutes (approximately 9 × 9 km at the equator).
- Time step: daily.
- Water-relating infrastructure: Flow control is included through dam operation rules, water conveyance is considered by incorporating small-scale channels, and water supply is adjusted by considering seawater desalination.
- Evaluation period: water demand and development of infrastructure are based on recent reports of social conditions, while weather conditions are evaluated for the 40-year period from 1980 to 2020.
2. Post-proecessing
The H08 model's daily and grid-based evaluation results (available freshwater resources and water demand by sector) are first aggregated both temporally and spatially. Temporal aggregation varies by indicator, but the minimum aggregation unit is 1 month. Spatial aggregation is performed at the sub-basin scale to match the terrain data employed by the model. Each indicator is then calculated statistically from the post-processed data.
3. Assessment of Future Water Scarcity Based on Multiple Scenarios of Climate and Social Change
Water Security Compass beta provides projections of water demand, available water resources, and water scarcity indexes for three future scenarios, targeting the years 2030 and 2050. The same H08 model used for historical evaluations is employed for future assessments, with socioeconomic and climate conditions set for each future pathway (Table 1). Information on future daily weather conditions corresponds to the ISIMIP dataset [2], which are five bias-corrected CMIP6 climate models. The information provided by Water Security Compass beta represents the average of the results obtained when modeling with the information of each of the five climate models. Future water demand is assessed using the methodology of Hanasaki et al. 2013 [3], with future projections of population, GDP, and electricity generation provided by the SSP Public Database (Version 2.0) [4]. Changes in water use efficiency, irrigated area, and other factors are aligned with the SSP narrative scenarios.
| Pathways | Shared Socioeconomic Pathways (SSP) Representative Concentration Pathways (RCP) |
Water Use |
|---|---|---|
| Sustainability -Taking the Green Road |
SSP1-RCP2.6 Global population growth (Low)Global economic growth (Medium-high) Global energy use (Low)Technology development (High) |
Water use efficiency (High) Irrigated are growth (Low)Crop intensity (Low) |
| Regional Rivalry - A Rocky Road |
SSP3-RCP7.0 Global population growth (High)Global economic growth (Low) Global energy use (Medium-high)Technology development (Low) |
Water use efficiency (Low) Irrigated are growth (High)Crop intensity (High) |
| Fossil fueled Development - Taking the Highway |
SSP5-RCP8.5 Global population growth (Low)Global economic growth (High) Global energy use (High)Technology development (High) |
Water use efficiency (High) Irrigated are growth (High)Crop intensity (High) |
Assessment of regional water scarcity using data with higher spatial resolution (Japan viewer)
In the Japan domain version, as with the global version, the evaluation is based on the H08 model’s calculation results. The main difference between the Japan version and the global version lies in the spatial resolution of the input data to the H08 model and the method used to create it. The Japan version uses a 1-minute spatial resolution (about 2 km), which is more detailed than the global version that is 5-minute (about 9 km). The input data includes data on meteorological conditions, agricultural land cover, water demand, dams, canals, and other relevant factors available in Japan (related articles: [7]-[9]).
As of July 2024, the Japan version is in its alpha phase. Index values may change in the future as the work to improve data accuracy on canals and reservoirs, particularly in coastal areas.Reference:
[1] Hanasaki et al. (2018), A global hydrological simulation to specify the sources of water used by humans. Hydrol. Earth Syst. Sci. 22, 789–817. DOI.
[2] Stefan Lange, Matthias Büchner (2021): ISIMIP3b bias-adjusted atmospheric climate input data (v1.1). ISIMIP Repository. DOI.
[3] Hanasaki et al. (2013), A global water scarcity assessment under Shared Socio-economic Pathways -Part 1: Water use.Hydrol. Earth Syst. Sci. 17, 2375-2391. DOI.
[4] SSP database hosted by the IIASA Energy Program at URL.
[5] O’Neill, B. C. et al. (2016), The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6. Geosci. Model Dev. 9, 3461–3482. DOI.
[6] Riahi, K. et al. (2017), The Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas emissions implications: An overview. Glob. Environ. Chang. 42, 153–168. DOI.
[7] Hanasaki et al. (2022), Toward hyper-resolution global hydrological models including human activities: application to Kyushu island, Japan, Hydrol. Earth Syst. Sci., 26, 1953–1975. DOI.
[8] Oda et al. (2024). ASSESSMENT OF WATER DEMAND AND SUPPLY BALANCE IN TOKYO BY MODELLING ITS WATER DISTRIBUTION SYSTEM: STUDY ON WATER SUPPLY OF GLOBAL HYDROLOGICAL MODELS, Japanese Journal of JSCE, 2024, Volume 80, Issue 16. DOI.
[9] Kawasaki et al. (2024). CONSIDERING THE IRRIGATION CANAL NETWORK IN JAPAN AN ATTEMPT TO MODEL INTER-BASIN WATER CONVEYANCE, Japanese Journal of JSCE, 2024, Volume 80, Issue 16. DOI.