GCRI · Water Nexus
Drinking water and sanitation
Safe drinking water and sanitation are counted in whether a household’s water is available when needed, free from contamination and on the premises, and whether excreta are safely contained, treated and disposed. The counting is global, the delivery is local, and the gaps open fastest in crises. This page sets out how access and safety are measured and what the evidence serves.
How the work runs.
Fig.Utility operations: example names and illustrative values, not a record or a live system.
Drinking water and sanitation: how the risk develops.
Treatment, safety, infrastructure and equity. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.
The service ladder
Access is classed from surface water to safely managed service. Moving up the ladder needs infrastructure, management and affordability together; any one missing drops the rung.
Contamination pathways
Faecal contamination enters through broken pipes, intermittent supply, unsafe storage and poor sanitation nearby. Microbial risk rises sharply during floods and outages.
Chemical hazards
Arsenic, fluoride, nitrate and lead are geogenic or infrastructural, chronic rather than acute, and invisible without sampling.
Crisis and displacement
Disasters and displacement multiply the population per source and collapse sanitation first. Outbreaks follow within weeks unless provision is planned.
Water now in the Nile Basin.
Rain, flood water and population density over the Nile Basin, from NASA GIBS. Each layer carries its own date.
The interactive map needs JavaScript; the layer list and sources are below.
Layers 3
Water now, for this page
About this layer
- Evidence
- Estimated
- Source
- GPM IMERG (NASA GES DISC)
- Provider
- NASA GES DISC
- Licence
- NASA open data
- Vintage
- daily; Satellite estimate, near real time
- Newest at build
- 2026-10-12
- Resolution
- about 2 km grid
- Uncertainty
- Satellite estimate, near real time. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed (clouds leave gaps)
- Source
- VIIRS Global Flood Product (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- daily; Satellite detection; clouds leave gaps
- Newest at build
- 2026-10-14
- Resolution
- about 250 m grid
- Uncertainty
- Satellite detection; clouds leave gaps. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Estimated
- Source
- Gridded Population of the World v4.11 (NASA SEDAC (CIESIN, Columbia University))
- Provider
- NASA SEDAC (CIESIN, Columbia University)
- Licence
- CC BY 4.0
- Vintage
- null; Census-based estimate, static (2020)
- Resolution
- about 1 km grid
- Uncertainty
- Census-based estimate of people per square kilometre in 2020, shown as exposure context; not a count of people affected by any hazard.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Modelled
- Source
- SMAP Level 4 (NASA NSIDC DAAC)
- Provider
- NASA NSIDC DAAC
- Licence
- NASA open data
- Vintage
- daily; Model with satellite data assimilated
- Newest at build
- 2026-10-11
- Resolution
- about 2 km grid
- Uncertainty
- Model with satellite data assimilated. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed
- Source
- VIIRS NOAA-20 corrected reflectance (NASA LANCE)
- Provider
- NASA LANCE
- Licence
- NASA open data
- Vintage
- daily; Satellite image
- Newest at build
- 2026-10-14
- Resolution
- about 250 m grid
- Uncertainty
- Satellite image. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
About this layer
- Evidence
- Observed (latest month GIBS publishes)
- Source
- GRACE-FO JPL mascons (NASA JPL PO.DAAC)
- Provider
- NASA JPL PO.DAAC
- Licence
- NASA open data
- Vintage
- monthly; Satellite gravimetry; latest month GIBS publishes
- Newest at build
- 2022-07-01
- Resolution
- about 2 km grid
- Uncertainty
- Satellite gravimetry; latest month GIBS publishes. Satellite or model raster as the provider publishes it. Clouds, swath gaps and retrieval error leave gaps and noise; values are indicators, not measurements at a place.
- Reached through
- gibs.earthdata.nasa.gov, only after you allow the live map
Keyboard, with the map focused
Hold Ctrl or ⌘ and scroll to zoom
Latest available
NASA GIBS / EOSDIS · ASTER GDEM (METI, NASA) · Blue Marble (NASA) · © OpenStreetMap contributors (ODbL) · Natural Earth
Loading the latest NASA imagery.
Drag to move. Ctrl or ⌘ and scroll, pinch or the buttons to zoom; hover for the values under the pointer; reset returns to the region.
Water now, framed on the Nile Basin.Satellite and model products as NASA publishes them, each with its own date. They are indicators, not assessments of any place.
Data: NASA GIBS · ASTER GDEM · Blue Marble · © OpenStreetMap contributors · Natural Earth · NASA EONET · NASA JPL OPERA DIST-ALERTSources and licences
- We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- GPM IMERG precipitation, NASA Precipitation Processing System; distributed by the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- VIIRS near-real-time products (flood, land surface temperature, snow cover, corrected reflectance), NASA LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- Center for International Earth Science Information Network (CIESIN), Columbia University. 2018. Gridded Population of the World, Version 4 (GPWv4): Population Density, Revision 11. NASA Socioeconomic Data and Applications Center (SEDAC). Licensed under CC BY 4.0. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). doi:10.7927/H49C6VHW. CC BY 4.0
- SMAP Level 4 soil moisture and snow mass, NASA Global Modeling and Assimilation Office; distributed by the NASA National Snow and Ice Data Center DAAC; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- GRACE and GRACE-FO JPL mascon solution, NASA Jet Propulsion Laboratory; distributed by the NASA Physical Oceanography DAAC (PO.DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- ASTER GDEM is a product of METI and NASA (ASTER Global Digital Elevation Model V003, NASA LP DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). Cite as: NASA/METI/AIST/Japan Spacesystems and U.S./Japan ASTER Science Team (2019). ASTER Global Digital Elevation Model V003. doi:10.5067/ASTER/ASTGTM.003. NASA open data
- Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com. Public domain
- © OpenStreetMap contributors (ODbL), via NASA GIBS (coastlines, boundaries, roads and place names). Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). ODbL
- Blue Marble, NASA Earth Observatory; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into hexagonal cells where shown (modified). NASA open data
- Context on the globe and flat map: coastlines, boundaries, roads and place names from NASA GIBS reference layers (OpenStreetMap data, ODbL, © OpenStreetMap contributors); Blue Marble imagery as an optional base; 3D terrain and the elevation read-out from the ASTER GDEM elevation colour index (5 m to 200 m classes, exaggerated for legibility). Boundaries are drawn as published and imply no position on any territory.
- Live events: NASA Earth Observatory Natural Event Tracker (EONET); events are indicative and keep their original source links.
- Live: NASA EONET Events are indicative, not authority warnings.
- Observed (EO): NASA JPL OPERA DIST-ALERT (contains modified Copernicus Sentinel data 2026). We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS).
- NASA GIBS: We acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS).
- River discharge forecast, 30 days with range (GloFAS via Open-Meteo): Contains modified Copernicus Emergency Management Service information 2026; not a flood warning.
- Past year, daily temperature (ERA5 via Open-Meteo): Contains modified Copernicus Climate Change Service information 2026.
- Past year, daily temperature and sunshine (NASA POWER): These data were obtained from the NASA Langley Research Center (LaRC) POWER Project funded through the NASA Earth Science/Applied Science Program..
- Weather data by Open-Meteo.com (https://open-meteo.com/), licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).
- Optional layers (14 sources in the layer list: live, forecast, observed and context) print their provider credit on the map and here when switched on; forecasts are model output and derived indices are estimates.
Layers and dates
- Precipitation rate, daily mean: GPM IMERG, NASA GES DISC · 12 Oct 2026
- Flood water, 3-day composite: VIIRS Global Flood Product, NASA LANCE · 14 Oct 2026
- Population density, 2020: Population: CIESIN, Columbia University, Gridded Population of the World v4.11 (2018), NASA SEDAC, CC BY 4.0 · static
- Root-zone soil moisture, 0 to 100 cm: SMAP Level 4, NASA NSIDC DAAC · 11 Oct 2026
- True colour: VIIRS NOAA-20 corrected reflectance, NASA LANCE · 13 Oct 2026
- Water storage anomaly, monthly: GRACE-FO JPL mascons, NASA JPL PO.DAAC · July 2022
Safe water and sanitation depend on power, chemicals, staff and healthy catchments.
| Domain | How it couples here | What to watch |
|---|---|---|
| Energy | Pumping and treatment stop without electricity; standby generators need fuel. See grid disruption and recovery. | Hours of backup at treatment works and pumping stations |
| Health | The WHO Guidelines for Drinking-water Quality set the health basis; failures appear as diarrhoeal disease, cholera and typhoid. See infectious threats. | Escherichia coli detections; disease surveillance after outages |
| Food | Unsafe water used for irrigation and food processing carries pathogens into the food chain. | Wastewater reuse practices and their controls |
| Biodiversity | Untreated sewage degrades rivers and coasts; healthy catchments reduce treatment burden. | Share of wastewater safely treated (SDG 6.3.1) |
Coverage is reported by the WHO/UNICEF Joint Monitoring Programme on service ladders: safely managed, basic, limited, unimproved and surface water. The ladders separate access from quality and reliability, which national averages often blur.
Model drinking water and sanitation as a system. Run the cascade.
Assembled from the Nexus Standards area profile Water risk standards: the hazards it names, the systems and sectors that carry the loss, the controls that dampen it and the data that observe it. Choose the components, pick an initiating hazard and step through the cascade. The Map view places the run on an example geography with open data. Every coupling weight is a stated assumption you can change. A teaching model, not a forecast, an assessment or a certification. To model a place of your own choosing, open the full System Builder.
Hazards
- Flash flood
- Meteorological drought
- Groundwater depletion
- Dam failure
- Debris flow (set off downstream)
- Agricultural drought (set off downstream)
- Hydrological drought (set off downstream)
- Wildfire (set off downstream)
- Peat and underground fire (set off downstream)
- Forest dieback (set off downstream)
- Water supply shortfall (set off downstream)
- Acute food crisis (set off downstream)
- Dust storm (set off downstream)
- Land subsidence (set off downstream)
- Saltwater intrusion (set off downstream)
- River flood (set off downstream)
- Mass displacement (set off downstream)
- Amazon rainforest dieback (set off downstream)
Systems and couplings
- Water risk standards
- Energy risk standards Common driver and cascade
- Food and agriculture risk standards Cascade
- Health risk standards Cascade
- Hydrometeorological hazard standards Shared hazard records
Controls
NS-0Constitution and principlesNS-1The UNI and the artefact catalogue (grammar v0.2: domain, sector, region and environment segments)NS-3Risk record UNIs (grammar, legacy crosswalk, allocation authority)NS-3bDataset and product metadata profile (STAC, DCAT, PROV-O)NS-9Contextual UNIs (deployments, instances, programme instances)NS-10Policies and clauses (machine-readable obligations: definition, binding, evaluation and enforcement)NS-11Verification and monitoring (evidence, attestations, zero-trust conformance observation)NRS-U28Universe platform profile: Water NexusNRS-H61Hazard family: Cascading failure (NHS-1 sys.cascade)NRS-K42Domain pack profile: Cross border basins (DOMAIN-042)NRS-N1Water risk and resilienceNRS-N7Water-energy-food-health-biodiversity-infrastructure nexus couplingNRS-H62Hazard family: Compound and multi-hazard events (NHS-1 sys.compound)
Observation
- USGS Water Data APIs (listed for reference)
- GloFAS global flood forecasts and reanalysis (listed for reference)
- GRACE/GRACE-FO terrestrial water storage mascons (listed for reference)
- Aqueduct 4.0 Water Risk Atlas (listed for reference)
- CHIRPS quasi-global gridded precipitation (listed for reference)
- Level of water stress: freshwater withdrawal as a proportion of available freshwater resources
- Proportion of transboundary basin area with an operational arrangement for water cooperation
- Proportion of population using safely managed drinking water services
- Number of disruptions to basic services attributed to disasters
Example geography
- The Ganges and Brahmaputra Basin: 178 hexagonal cells
- Surface water through cloud, 30 m (OPERA DSWx-S1 radar), NASA GIBS
- Rain rate, last half hour (IMERG), NASA GIBS
- Surface soil moisture (SMAP), NASA GIBS
- Night lights tonight, outages (VIIRS Day/Night Band), NASA GIBS
Water safety evidence and who can add to it.
Studies of service continuity and water safety planning are designed for the Country Quarterly series and the Evidence Brief series. The Global Centre for Risk and Innovation (GCRI) does not regulate or inspect water services; the responsible regulator and utility decide. Water quality datasets would carry NS-3b metadata under the proposed Nexus Standards, with household-level data never published.
- Utility outage logs with causes and durations.
- Water safety plan reviews a utility is willing to publish.
- Community reports of service failure, through consent-aware routes.
The sector signature of drinking water and sanitation.
The sectors drinking water and sanitation touches and how strongly they depend on each other: what a study has to observe and model together.
Signature
Water and its partners
Water gives irrigation to food (0.8), cooling water and hydropower to energy (0.6) and environmental flows to biodiversity (0.6).
W · E · I · F · H · B
- Sectors
- 4 of 6
- Relations
- 6 of 15
- Coupling
- 0.43 share of total
Strongest relations in play
- Food → Biodiversity · land conversion0.6
- Water → Energy · cooling water and hydropower0.6
- Water → Food · irrigation0.8
- Water → Biodiversity · environmental flows0.6
What is measured, and how well.
Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.
| Indicator | Unit | Cadence | Source type | Label |
|---|---|---|---|---|
| Population with safely managed drinking water | percent | annual | Household surveys, administrative data | Published statistics |
| Population with safely managed sanitation | percent | annual | Household surveys, administrative data | Published statistics |
| E. coli detection in supply samples | percent of samples positive | monthly | Laboratory sampling | OBSERVED |
| Arsenic and fluoride exceedance | percent of sources above guideline | survey | Source testing | OBSERVED |
| Intermittency | hours of supply per day | daily | Utility records, sensors | OBSERVED |
| Persons per functioning water point | persons | per site | Site assessments | ESTIMATED |
How drinking water and sanitation is modelled, measured and tested.
The model, its assumptions, its data and its uncertainty, in the form a scientist or engineer would check. Structures follow published methods. The values drawn are illustrative, not findings.
System model
The couplings between the systems in drinking water and sanitation: signs of influence, a reinforcing and a balancing loop, and cross-links where stress jumps.
Where the evidence comes from.
Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.
| Source | What it gives | Licence class |
|---|---|---|
| WHO and UNICEF Joint Monitoring Programme | National and subnational access estimates and the service ladders | Free and open, attribution |
| Demographic and Health Surveys and MICS | Household-level water and sanitation data | Terms per survey programme |
| National water quality surveillance | Sampling results by supply and source | By agreement with each agency |
| Water Point Data Exchange | Rural water point functionality records | Open, attribution |
| Humanitarian cluster assessments | Crisis-period provision and gaps | Terms per cluster |
Who decides, and what the evidence serves.
Water Nexus prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.
| Who decides | The question | Evidence this page serves |
|---|---|---|
| Health and water ministries | Where safely managed service is furthest from target and what closes the gap | Access maps with uncertainty; contamination risk by supply type |
| Utilities and local authorities | Which supplies need continuous chlorination, pipe renewal or storage advice | Sampling results against intermittency and outage records |
| Humanitarian coordinators | Where provision is below standards and outbreak risk is rising | Persons per water point, sanitation coverage, surveillance signals |
Outputs this topic produces
- Access maps by service ladder rung with survey uncertainty
- Contamination risk layers by supply type and season
- Crisis provision gaps by population and site
- Monitoring designs for utilities and health agencies
What WASH researchers and engineers ask.
- Is the water safe at the point of use, not just at the treatment works?
- Which hazards, microbial, chemical or radiological, threaten a supply, and where do they enter?
- Is wastewater collected, treated and returned without harming people or ecosystems?
- Who lacks reliable access, and why?
From source to tap to return.
Safety rests on multiple barriers: protecting the source, treating water by coagulation, filtration and disinfection, maintaining pressure and residual disinfectant in the network, and safe storage in homes. A failure at any barrier, such as low pressure that lets contaminated groundwater enter pipes, can undo the others.
Sanitation separates people from excreta. Where it fails, pathogens reach water sources and spread diarrhoeal and other diseases, with the heaviest burden on young children. Floods, power cuts and drought can disable treatment and sewerage at the moment communities need them most. Emerging contaminants and antimicrobial resistance add new questions.
How safety and access are assessed.
- 01
Risk-based management
Water safety planning identifies hazards and control measures from catchment to consumer. Its value depends on regular verification and honest records.
- 02
Monitoring
Laboratory and field testing, increasingly supported by online sensors and observation networks. Sampling captures moments, not continuous conditions.
- 03
Surveys and service data
Household surveys and utility records describe access, reliability and affordability. Informal settlements and intermittent supplies are often under-recorded.
How it is studied, and what the methods cannot say.
- 01Water and environmental engineeringTreatment and distribution resilience · Water safety planningApplied here
- 02Spatial statistics and geostatisticsRainfall and groundwater interpolation · Regionalisation to ungauged basinsApplied here
- 03Sensors, IoT and observation networksGauge and well telemetry · Utility network monitoring · Low-cost sensing with stated uncertaintyApplied here
- 04Geospatial information systemsExposure mapping · Catchment and basin delineation · Public-safe basin mapsApplied here
- 05Uncertainty quantification and model validationEnsemble and parameter uncertainty · Propagation through the cascade · Evidence labellingApplied here
Where this page’s references lead.
The bodies and documents this page is read against. Status and editions change; each link goes to the issuing body.
- WHO Guidelines for Drinking-water Quality, fourth edition incorporating the first and second addenda (WHO, 2022)
- Water Safety Plan Manual, second edition (WHO, 2023)
- WHO/UNICEF Joint Monitoring Programme for Water Supply, Sanitation and Hygiene, progress reports (latest 2025)
- NS-3b, Dataset and product metadata profile, a proposed standard
Questions and answers.
What does safely managed mean?
Why can a city with pipes still lack safe water?
How quickly do outbreaks follow a disaster?
Is treated water always safe at the tap?
Why does sanitation matter for water risk?
What changes when supply is intermittent?
Does Water Nexus rank utilities on water safety?
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