Environmental flow assessment
Flow records and hydraulic models are linked to the habitat needs of fish, vegetation and wetlands to define the flow regime that sustains them.
The Global Centre for Risk and Innovation (GCRI)
Hydrology connects biodiversity to water: flow regimes shape freshwater habitats, wetlands store and release water, and catchment condition affects the quantity and quality of water reaching people. It quantifies the water services ecosystems provide and the flows ecosystems themselves need.
Environmental flows are the quantity, timing and quality of water needed to sustain freshwater and estuarine ecosystems and the people who depend on them. Hydrology quantifies them, along with the water services ecosystems provide, from flood storage in wetlands to cleaner water from healthy catchments.
The working screen behind this method: its structure, terms and states. Names are placeholders and values illustrative.
Biodiversity · Hydrology for ecosystems · Run R-6654
held-out period
| T+2 | 0.21 | 0.14 | 0.22 | Skilful |
| T+4 | 0.21 | 0.19 | 0.38 | Skilful |
| T+6 | 0.36 | 0.25 | 0.19 | Skilful |
| T+8 | 0.20 | 0.20 | 0.18 | Skilful |
Hydrology studies the movement, distribution and quality of water across the land surface, subsurface and atmosphere. It underpins the assessment of floods, droughts and water supply, which affect food, energy, health and infrastructure together. In biodiversity and nature, climate and hazards and oceans and coasts, hydrological estimates set design standards for dams, levees and drainage and inform water allocation between competing users. They link climate hazards to downstream effects on power generation, crops and public health. The canonical description is on the STEM Commons.
Flow records and hydraulic models are linked to the habitat needs of fish, vegetation and wetlands to define the flow regime that sustains them.
Rainfall-runoff and routing models are run with and without floodplain storage or forest cover to estimate how ecosystems change flood peaks downstream.
Sediment and nutrient models trace how land cover and erosion upstream affect water quality at intakes, reservoirs and coastal habitats.
Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.
| Term | Definition |
|---|---|
| Flow regime | The pattern of a river's flow over time, including magnitude, timing, frequency, duration and rate of change. |
| Flood regulation service | The reduction of flood peaks by wetlands, floodplains and forests that store or slow water. |
| Sediment retention | The trapping of eroded soil by vegetation and wetlands before it reaches rivers and reservoirs. |
Rivers, lakes and how far each division sits from mapped surface water, shown for the Mekong Basin as an example geography for this subject.
Data from the source register feeds the methods; calibration and an independent test gate the estimate and its limits; the decision stays with the competent authority.
Fig. 01Nodes carry their type, metrics and state; connectors show what feeds what; the gates are the validation steps; the timeline is one application. Design of the method's use, not a record of a run.
Datasets and records used by hydrology and water science on this platform, with the role each plays and the label its values carry. Sources are listed in the source register.
| Data | Role | Label |
|---|---|---|
| Stream gauge records | Flow regime and calibration | OBSERVED |
| JRC Global Surface Water | Wetland and floodplain inundation | OBSERVED |
| HydroSHEDS river networks | Catchment delineation and connectivity | MODELLED |
| Water quality monitoring | Nutrient and sediment loads | OBSERVED |
Models are calibrated on one period of observed flows and tested on an independent period or neighbouring catchment. Skill scores and comparison with surveyed flood extents are used to judge performance.
| Check | How it is done |
|---|---|
| Split-sample calibration | Models are fitted on one period and tested on another, with test-period skill reported |
| Ecological response validation | Flow-ecology relationships are checked against field surveys of the species or habitats they claim to support |
| Paired scenario runs | With-and-without ecosystem runs use the same forcing so that differences can be attributed |
Assumptions of stationarity weaken as climate and land use change. Ungauged basins, karst aquifers and rapid urbanisation are poorly represented by parameters fitted elsewhere.
Water Nexus stewards hydrology and water science for the Consortium and reviews how it is applied across platforms.
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.