The Global Centre for Risk and Innovation (GCRI)
The methods Water Nexus relies on, the assumptions they carry and the limits of what they can show.
Water · Methods and uncertainty
unit · cadence · label
| Reservoir storage | of capacity | daily | OBSERVED | SP-8666 |
| Streamflow at outlet | m³/s | 15 min | OBSERVED | SP-5025 |
| SPI-3 | index | monthly | DERIVED | SP-0773 |
| E. coli compliance | samples | weekly | OBSERVED | SP-1926 |
| Environmental flow | m³/s | daily | MODELLED | SP-5086 |
Water Nexus · Evidence registerEvidence register, in outline: domain structure with placeholder names and illustrative values, not a record.
The Water Nexus methods page sets out the methods the platform relies on, among them hydrology and water science, water and environmental engineering, and geospatial information systems, with their assumptions, validation and limits. Each analysis lists its assumptions and data, reports ranges and confidence beside central estimates, is checked against observations or other models, and states what it cannot show.
Fig.How a finding is reviewed before it is published. Design, not a record.
Rivers, lakes and how far each division sits from mapped surface water, shown for the Lake Chad Basin as an example geography for this subject.
| Source | Typical size | How it is reported |
|---|---|---|
| Rainfall input | Large in convective and mountain climates; gauge networks are sparse | Ensembles of rainfall products; spread carried to flow |
| Model structure | Differs most in low flows and groundwater exchange | Multi-model comparison on the same basin |
| Parameters | Equifinality: many parameter sets fit the same record | Ranges from calibration, not a single best fit |
| Non-stationarity | Grows with horizon and land-use change | Trend-aware extreme value models, scenario sets |
| Human operations | Reservoir rules and abstractions often undocumented | Stated assumptions, sensitivity runs |
A flow estimate is published with its range and the evidence label of each input. Return periods are reported with confidence intervals, and a design value is never quoted without the period of record it rests on.
Each analysis lists its assumptions and the data it depends on.
Ranges and confidence are reported alongside central estimates.
Models are checked against observations and, where possible, against other models.
What an analysis cannot show is stated beside what it can.
Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.
| Term | Definition |
|---|---|
| Uncertainty quantification | Characterising and propagating the uncertainties in a model to state confidence in its outputs. |
| Sensitivity analysis | Repeating an analysis under different assumptions to show how much the result depends on them. |
| Model validation | Comparing model predictions with independent observations to judge fitness for a stated use. |
| Hydrology and water science | Hydrology studies the movement, distribution and quality of water across the land surface, subsurface and atmosphere. |
The bodies and documents this page is read against. Status and editions change; each link goes to the issuing body.
The current service level is R0: information and enquiries. An enquiry receives a reference and names the next step; applications, payments, compute allocations and registrations open only when their team, terms and review capacity exist.