Irrigation supply and demand
Basin models compare crop water requirements with available river flow, storage and groundwater by season, showing where irrigation will be curtailed in a dry year.
The Global Centre for Risk and Innovation (GCRI)
Hydrology connects food production to the water that sustains it: rainfall, soil moisture, river flows, reservoirs and groundwater. In this field it quantifies irrigation supply and demand, the onset of agricultural drought and the flood exposure of farmland, and builds the water accounts on which allocation between farms, cities and ecosystems rests.
Hydrology for agriculture is the application of water science to farming: rainfall, soil moisture, river flow, reservoirs and groundwater as they supply crops and livestock. It quantifies irrigation supply and demand, the onset of agricultural drought and the flood exposure of farmland, and builds the water accounts that allocation rests on.
The working screen behind this method: its structure, terms and states. Names are placeholders and values illustrative.
Food · Hydrology for agriculture · Run R-9576
held-out period
| T+2 | 0.36 | 0.24 | 0.28 | Marginal |
| T+4 | 0.22 | 0.30 | 0.10 | Skilful |
| T+6 | 0.18 | 0.13 | 0.38 | Marginal |
| T+8 | 0.24 | 0.16 | 0.11 | 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 food and agriculture, trade, resources and supply chains and climate and hazards, 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.
Basin models compare crop water requirements with available river flow, storage and groundwater by season, showing where irrigation will be curtailed in a dry year.
Rainfall, soil moisture and streamflow indices are tracked together, so the onset of agricultural drought is identified when indicators agree rather than from one source alone.
Flood hazard maps and satellite flood extents are intersected with cropland and stores to estimate exposed area and the stage of the crop when water arrives.
Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.
| Term | Definition |
|---|---|
| Agricultural drought | A shortage of soil moisture during the growing season that reduces crop or pasture production. |
| Evapotranspiration | The combined loss of water from soil evaporation and plant transpiration, the main consumptive use of water by crops. |
| Water accounting | A systematic record of water supply, use and storage in a basin, by source and user, over a period. |
Rivers, lakes and how far each division sits from mapped surface water, shown for Iran 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 | Water availability | OBSERVED |
| CHIRPS rainfall | Drought indices | ESTIMATED |
| Satellite soil moisture (SMAP, SMOS) | Agricultural drought | MODELLED |
| Groundwater observation wells | Aquifer supply to irrigation | OBSERVED |
| FAO AQUASTAT | Agricultural water withdrawal | OFFICIAL |
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 calibrated on one period of record and tested on another |
| Water balance closure | Supply, consumption and return flows are reconciled, and residuals reported |
| Indicator agreement | Drought onset is checked across rainfall, soil moisture and flow indicators |
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.