The Global Centre for Risk and Innovation (GCRI)
Groundwater supplies drinking water to about half the world’s people and most of its irrigated agriculture, and it is the reserve that keeps rivers flowing through the dry season. Because it is unseen, it is easily over-drawn. This page sets out how aquifers store and release water, how depletion is measured, and what the evidence means for the institutions that license abstraction.
Water NexusWireframe of the working environment, not a live screen. Names and values are placeholders.
Groundwater depletion, recharge, contamination and rights. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.
An aquifer stores water in pores and fractures; recharge arrives from rainfall, river leakage and irrigation returns, slowly. The sustainable yield is bounded by recharge, not by what can be pumped.
Pumping beyond recharge lowers water tables, dries shallow wells first, and in compressible sediments compacts the aquifer and lowers the land permanently.
Falling heads draw in saline water on coasts and mobilise arsenic, fluoride and nitrate in some settings. Quality loss can end an aquifer’s use before quantity does.
Groundwater discharge is the baseflow of rivers; abstraction near a river takes from the river. Surface and groundwater are one resource governed as two.
Where this page’s subject sits in the world: boundaries and context now, the field layers when the interactive map loads.
MapWorld map in the Equal Earth projection, land and boundaries from Natural Earth (public domain). The interactive map loads through the Nexus Foundry plugin (globe or flat view).
The systems this subject touches, the method at its core and the decisions it informs.
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 |
|---|---|---|---|---|
| Depth to water table | metres below ground | monthly | Observation wells | OBSERVED |
| Terrestrial water storage anomaly | centimetres equivalent water height | monthly | Satellite gravimetry | ESTIMATED |
| Abstraction | cubic metres per year | annual | Licences and metering | OFFICIAL |
| Recharge estimate | millimetres per year | annual | Water balance, chloride mass balance, models | MODELLED |
| Land subsidence rate | millimetres per year | annual | Radar interferometry | OBSERVED |
| Electrical conductivity and chloride | microsiemens per centimetre; milligrams per litre | quarterly | Well sampling | OBSERVED |
The topic as a computational graph: named sources feed the methods, an evidence review gates the outputs, and the decisions stay with the authorities that hold them.
Fig. 02Nodes carry their type, two metric rows and a state; connectors show what feeds what; dashed frames name the owners; the timeline is the cadence. Design of the pipeline, not a record of a run.
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 |
|---|---|---|
| GRACE and GRACE-FO | Basin-scale water storage change | Public domain |
| Sentinel-1 interferometry | Ground deformation and subsidence | Free and open, attribution |
| National groundwater monitoring networks | Well levels, abstraction licences, quality sampling | By agreement with each agency |
| WHYMAP and national hydrogeological maps | Aquifer extent and type | Terms per map holder |
| GLDAS | Modelled soil moisture and groundwater components | Public domain |
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 |
|---|---|---|
| Licensing authorities | Whether abstraction can be licensed, capped or must be reduced | Storage trend from wells and gravimetry; recharge envelope; the gap between the two |
| Utilities and irrigation districts | How long current pumping can continue before yield or quality fails | Depth-to-water trends, conductivity trends, subsidence where relevant |
| Land-use and planning authorities | Where subsidence makes building and flood defence unsafe | Interferometric subsidence rates against abstraction |
Recharge occurs where rainfall or river water infiltrates through soil to the water table. Abstraction that exceeds recharge over years lowers water levels, increases pumping costs and can dry up springs and the baseflow that sustains rivers in dry seasons. In some aquifers, compaction as water is removed causes land subsidence that is largely irreversible. Near coasts, falling water levels can draw seawater inland.
Contamination comes from agriculture, sanitation, industry and mining, and from naturally occurring elements such as arsenic and fluoride. Because groundwater moves slowly, pollution can take decades to appear at a well and decades more to clear.
Water-level and water-quality monitoring in wells, often through sensors and observation networks. Many aquifers have few long records, and pumping wells give biased readings.
Satellite gravimetry and radar interferometry, part of Earth observation, detect large-scale storage change and subsidence, at coarse resolution.
Groundwater flow and transport models, with spatial statistics to interpolate between wells. Aquifer properties vary over short distances, so models carry wide uncertainty.
| Method | Applied here | Canonical page |
|---|---|---|
| Hydrology and water science | Hydrology and water science in this field | STEM Commons |
| Earth observation and remote sensing | Earth observation and remote sensing in this field | STEM Commons |
| Spatial statistics and geostatistics | Spatial statistics and geostatistics in this field | STEM Commons |
| Sensors, IoT and observation networks | Sensors, IoT and observation networks in this field | STEM Commons |
| Uncertainty quantification and model validation | Uncertainty quantification and model validation in this field | STEM Commons |
Satellite gravimetry resolves hundreds of kilometres, not a single well field. Recharge estimates by different methods disagree, often by a factor of two, and the page shows the envelope rather than a single number. Many abstraction records are incomplete, so modelled abstraction carries its own label.
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.