Current water storage conditions across the United States
The US-GDI uses daily GPS measurements of subtle ground motion to assess whether regional water storage is below normal, near normal, or above normal, providing insight into whether conditions are worsening or recovering.
Reading the map: Negative values indicate lower-than-normal hydrologic storage, values near zero indicate conditions near the historical expectation, and positive values indicate higher-than-normal storage for the selected time of year and accumulation window.
The US-GDI categories are storage-sensitive drought and wetness classes. Recent maps include rapid GPS products and are refined as final GPS solutions become available.
One view of integrated storage
The US-GDI is sensitive to combined regional water mass, including groundwater, soil moisture, snowpack, rivers, lakes, reservoirs, wetlands, and floodwater. Combined with other hydrologic observations and regional knowledge, the US-GDI can help identify distinct basin-scale storage characteristics and responses.
- Below normal
- Regional storage is lower than expected for this time of year.
- Near normal
- Regional storage is close to its historical seasonal expectation.
- Above normal
- Regional storage is higher than expected for this time of year.
The landscape responds to changing mass
Not all droughts are created equal.
A meteorological drought begins with a shortage of rain or snow. It describes an important drought driver, but the consequences of that shortage may take time to move through soils, streams, reservoirs, and aquifers.
A hydrologic drought develops when water stored across the landscape becomes depleted. It can emerge after precipitation declines and persist after wetter weather returns.
The US-GDI adds an independent, storage-sensitive line of evidence for evaluating whether regional water reserves are declining, stabilizing, or recovering.