- Global Water 2026
- Annex A
Methodology
How the edition was made: methods, the model card, the evidence cut and its age, the acceptance record and the glossary.
A.1Methods
The global baseline uses published values and four simple derivations. Each is shown in full so that any reader can reproduce it.
| No. | Derivation | Calculation | Result |
|---|---|---|---|
| (1) | Share of 2025 disaster losses from floods, storms and wildfires | 166 ÷ 224 | ≈ 74% |
| (2) | People lacking at least one WASH service (upper bound) | not additive, overlapping groups | reported separately |
| (3) | Freshwater against all-wildlife decline | 85 − 73 | 12 points steeper |
| (4) | Growth in water use over 40 years at about 1% a year | 1.01⁴⁰ | ≈ 1.5× |
| Strength | Definition |
|---|---|
| STRONG | a disruption in the source system has historically changed the target system’s service or output within one season, in more than one region |
| MODERATE | an effect is documented but buffered or slower |
| WEAK | an effect is plausible but not documented at global scale |
| Label | Rule |
|---|---|
| Reported | value as issued by its source, with year |
| Inferred | reasoned from cited evidence; never a measurement |
| Estimated | Nexus analytical value with stated method |
| Scenario | conditional on stated assumptions |
| Expert input | structured editorial judgement awaiting evidence |
A.2Model card, Water Sector Model v0
- Model ID
- MDL-GS01-WATER · v0.1
- Purpose
- represent the global water system and its couplings to energy, food, health and biodiversity
- Family
- graph-based system of systems
- Inputs
- the cited sources of this edition; no proprietary data
- Method
- expert-specified coupling strengths (STRONG · MODERATE · WEAK) from assessments and analogue events
- Validation
- none yet, first validation against federation evidence in 2027
- Uncertainty
- qualitative; strengths are hypotheses, not measurements
- Domain of validity
- global scale; not for basin, country or asset-level use
- Reproducibility
- strength table and sources published in this edition
20couplings
typed in v0
11strong
documented within one season
5moderate
documented, buffered
4weak
plausible, undocumented
A.3The baseline evidence cut
Every Nexus edition is published from a frozen evidence cut. The global baseline cut is documentary: it pins the exact edition of every source cited. Federation cuts begin with the first national Foundry cuts in 2027.
- Cut ID
- DC-SECTOR-WATER-GLOBAL-2026-B0
- Type
- baseline documentary cut
- Resolution policy
- pinned · as of 30 September 2026
- Sources pinned
- 48 cited sources, each at the edition and retrieval date in the references
- Model runs
- none at baseline, analytical values are stated with their method
- Digest
- computed at freeze and recorded in the publication record
- Supersedes
- nothing, first cut of the series
- Superseded by
- the 2027 water annual cut
Lineage
- 01
source edition
- 02
pinned citation
- 03
finding
- 04
page
- 05
publication record
| Element | Baseline 2026 | 2027 global annual |
|---|---|---|
| Sources | cited global publications, pinned by edition | national, regional and sector cuts through one graph |
| Analysis | stated methods and editorial estimates | typed analysis specifications |
| Models | Water Sector Model v0 specification | model runs with receipts |
| Findings | twelve baseline findings | findings re-bound to federation evidence |
| Review | five passes scheduled | five passes on the exact digest |
A.4Evidence age and coverage
A 2026 global edition rests on evidence observed in many different years. This page shows each time base, so that no single year label hides older evidence.
| Indicator | Observed | Released | Cadence | Next release |
|---|---|---|---|---|
| Drinking water and sanitation access | 2022 | Jul 2023 | biennial | next JMP update |
| Severe seasonal water scarcity | multi-year | 2016 · 2024 | periodic | next UNWWDR |
| River discharge anomalies | 2023 | Oct 2024 | annual | annual |
| Glacier mass loss | 2023 | Oct 2024 | annual | annual |
| Groundwater trends | 1980–2022 | Jan 2024 | periodic | new studies |
| WASH-attributable deaths | 2019 | 2023 | periodic | next WHO update |
| Freshwater wildlife index | 1970–2020 | Oct 2024 | biennial | 2026 edition |
| Wetland extent | 1970–2025 | Jul 2025 | periodic | next outlook |
| Flood and storm losses | 2025 | Jan 2026 | annual | Jan 2027 |
| Transboundary arrangements | 2023 | 2024 | triennial | 2027 |
| System | Coverage | Thinnest dimension |
|---|---|---|
| Access | GOOD | reliability during droughts and floods |
| Hydrology | GOOD | basin-scale storage |
| Cryosphere | GOOD | glacier-fed basin flows |
| Groundwater | PARTIAL | levels and recharge |
| Water quality | THIN | monitoring in fast-growing cities |
| Use by sector | PARTIAL | data-centre and mining use |
| Freshwater nature | GOOD | condition outside monitored sites |
| Governance | PARTIAL | operational status of arrangements |
A.5Evidence cards, two anchor sources
Issued by WHO and UNICEF from household surveys, censuses and administrative data. Biennial, with service ladders from basic to safely managed. Role: binds WAT-001 and the access tiles.
EVD-GS01-001
JMP 2023 drinking water, sanitation and hygiene1
Issued by the World Meteorological Organization from hydrological observations, models and satellite products. Annual. Role: binds WAT-004 on river discharge and glacier loss.
EVD-GS01-002
State of Global Water Resources 20235
| Dimension | EVD-GLB-001 | EVD-GLB-002 |
|---|---|---|
| Completeness | gaps in fragile settings; modelled estimates | uneven station coverage; modelled fill |
| Timeliness | about 18 months after the year | about ten months after the year |
| Revision | series revised as surveys arrive | revised as observations improve |
| Method transparency | methods published | methods published |
| External validation | national statistical review | multiple data products compared |
Evidence cards to follow in 2027
A.6Publication acceptance record
Editorial self-check at evidence close. Every applicable item carries a disposition; the remaining items are review, approval and deposit.
| Group | Area | Items | Pass | N/A | Pending |
|---|---|---|---|---|---|
| D1 | Identity and scope | 8 | 8 | 0 | 0 |
| D2 | Source and data | 12 | 9 | 1 | 2 |
| D3 | Analysis and models | 12 | 3 | 8 | 1 |
| D4 | Findings and claims | 9 | 8 | 0 | 1 |
| D5 | Figures, tables, maps | 10 | 6 | 2 | 2 |
| D6 | Editorial and citations | 10 | 8 | 0 | 2 |
| D7 | Review and approval | 13 | 0 | 0 | 13 |
| D8 | Artefact and design | 12 | 7 | 0 | 5 |
| D9 | Registry and release | 9 | 0 | 0 | 9 |
Publication gate
- Conditions met
- 14 of 23 at evidence close
- Blocking problems
- none recorded
- Open conditions
- reviews, approval of the exact digest, deposit, registry pointer
Not applicable at baseline
- Model runs
- first runs in Q1 2027
- Maps
- plates in Q2 2027
- Waivers
- none
A.7Status words
| Status | What it means |
|---|---|
| Observed | Measured directly and published by the source. |
| Reported | Published statistics of an official or institutional source. |
| Declared | Stated by the body concerned; not independently measured. |
| Estimated | A Nexus estimate from cited evidence, with its method in Annex A. |
| Modelled | Produced by a stated model from cited inputs. |
| Inferred | Reasoned from cited evidence; not measured. |
| Forecast | A projection by the cited source. |
| Simulated | A simulation result under stated assumptions. |
| Scenario | A conditional statement under stated assumptions; never a prediction. |
| Expert input | Expert judgement, recorded with its basis. |
| Candidate | Proposed for a later edition; not yet evidence. |
| Evidence-quality levels (EQL 1 to 5) grade the source behind a value; they are not a score of the subject. | |
A.8How the edition is made, released and corrected
Every edition is built from a sealed evidence cut, reviewed under three keys, signed and deposited before any site shows it as published; corrections go to Nexus Standards as change proposals and feed the next cut.
| Step | What happens | Source |
|---|---|---|
| 01 Evidence arrives from the pillars | Foundry seals observations and indicator series, Universe hands over after-action and scenario findings, and contributions are screened at every gateway, including this site’s. | |
| 02 The cut is sealed | On the cut date the evidence is pinned under one identifier, so anyone can rebuild the edition from exactly what it was built on. | |
| 03 The edition is assembled | The edition is drafted from its template and content pack. Agents may draft; they never publish and never decide. | |
| 04 The keys turn | The Global Risks Alliance turns the capital key: its steward checks that no finding reads as advice, a rating or an underwriting decision. No edition moves on until every key has been turned by a named steward. | |
| 05 The gate opens | A named approver releases one exact digest of the edition; any change after this point is a new version, never a silent edit. | |
| 06 Signed and deposited | The PDF, the web edition and the data bundle are signed together with a manifest and an RO-Crate description, and deposited on Zenodo with a concept and a version DOI. | |
| 07 Published on five sites | Only then do the five Reports sites show the edition as published, each reading it through its own lens. | |
| 08 Corrections go to Standards | Method and correction findings go to Nexus Standards as change proposals; citations, corrections and new contributions feed the next evidence cut. |
A teaching model of the process, not a forecast and not a record of any run; dates and counts on this page come from the programme record. Sources: Reports governance at Global Risks Alliance (2026); Zenodo, repository of record for Reports deposits (2026).
Lifecycle, one state at a time: Draft, Computed, Evidence bound, Reviewed, Approved for release, Published, Corrected, Superseded. This edition is a draft.
A.9Glossary and abbreviations
| Term | Meaning |
|---|---|
| Baseline Edition | the inaugural annual edition that fixes the reference state for the series |
| WEFH+B | water, energy, food, health and biodiversity, the national nexus core |
| Coupling | a typed dependency through which one system transmits to another |
| Protection gap | the share of losses not covered by insurance |
| Capability ladder | LISTED → EXISTS → ADEQUATE → TESTED → DEMONSTRATED |
| EQL | evidence-quality level, 1–5 |
| Evidence cut | a frozen resolution of exact sources and versions |
| NNC · NLC · NWG | National Nexus Consortium · National Leadership Council · National Working Groups |
| Abbreviation | Expansion |
|---|---|
| AQUASTAT | FAO global information system on water and agriculture |
| GloFAS | Global Flood Awareness System |
| GRACE-FO | Gravity Recovery and Climate Experiment Follow-On satellites |
| GRDC | Global Runoff Data Centre |
| HydroSOS | WMO Hydrological Status and Outlook System |
| JMP | WHO/UNICEF Joint Monitoring Programme |
| SDG 6 | Sustainable Development Goal 6, clean water and sanitation |
| SOLAW | The State of the World’s Land and Water Resources for Food and Agriculture |
| TNFD | Taskforce on Nature-related Financial Disclosures |
| UNECE | United Nations Economic Commission for Europe |
| UNWWDR | United Nations World Water Development Report |
| WASH | water, sanitation and hygiene |
| WMO | World Meteorological Organization |
A.10Technical annex
| Item | Annex | Contents | Status |
|---|---|---|---|
| A.1 | Indicator definitions | the global indicator set, with units and sources | IN THIS EDITION |
| A.2 | Coupling strengths | the twenty-cell matrix and its rationale | IN THIS EDITION |
| A.3 | Scenario specification | SCN-GS01-MBD-01 assumptions and signposts | IN THIS EDITION |
| A.4 | Capability placements | rung evidence for fifteen functions | IN THIS EDITION |
| A.5 | Model diagnostics | first runs and validation | 2027 |
| A.6 | Sensitivity analyses | influence of coupling strengths | 2027 |
| A.7 | Basin notes | basin cards for the major shared basins | WITH REGIONAL EDITIONS |
| A.8 | Review statements | pass-by-pass review record | AT RELEASE |
A.1 · indicator definition, safely managed drinking water
- Construct
- drinking water from an improved source, on premises, available when needed and free from contamination
- Unit
- share and number of people
- Method
- JMP service ladder
- Source
- WHO/UNICEF JMP 20231
- Uncertainty
- modelled where survey data are missing
- Known limits
- does not measure reliability during drought or flood
Notes
Numbers are the edition’s reference numbers, so a note reads the same in every chapter. The full list, with every source and its licence, is in Annex C. Annex C, references
- 1WHO and UNICEF (eds.), Progress on Household Drinking Water, Sanitation and Hygiene 2000–2022: Special Focus on Gender. Joint Monitoring Programme, New York and Geneva, 2023.back
- 5WMO (ed.), State of Global Water Resources 2023. World Meteorological Organization, Geneva, 2024.back
- 4UNESCO World Water Assessment Programme (ed.), The United Nations World Water Development Report 2022: Groundwater, Making the Invisible Visible. UNESCO, Paris, 2022.back
- 17WWF (ed.), Living Planet Report 2024: A System in Peril. WWF, Gland, 2024.back
- 18Ramsar Convention Secretariat (ed.), Global Wetland Outlook 2025. Ramsar Convention Secretariat, Gland, 2025.back
- 9UNECE and UNESCO (eds.), Progress on Transboundary Water Cooperation: Global Status of SDG Indicator 6.5.2 and Acceleration Needs, 2024. United Nations, Geneva and Paris, 2024.back