Spatial Coverage

Global

The BTT platform presents freshwater information at the global scale at the HydroBASINS Level 05 sub-catchment level, with near-global coverage. Information at this scale is generated using a consistent methodology based on global hydrological models and environmental flow assessments.

In addition to the global dataset, the first version of the platform also incorporates local-scale information for the Rio Grande–Rio Bravo Basin at a finer spatial resolution than HydroBASINS Level 05. These local datasets are derived from streamflow gages distributed throughout the basin and provide basin-specific environmental flow assessments based on observed streamflow records rather than global hydrological model’s outputs.

Local: Rio Grande-Rio Bravo Basin

The Rio Grande–Rio Bravo Basin, one of the largest and most important transboundary river basins in North America. Originating in the San Juan Mountains of southern Colorado, the river flows through New Mexico and along the United States–Mexico border before discharging into the Gulf of Mexico. Extending over 1,600 miles, the basin covers approximately 870,000 km² across the U.S. states of Colorado, New Mexico, and Texas, as well as the Mexican states of Chihuahua, Coahuila, Nuevo León, Durango, and Tamaulipas.

The basin provides water for nearly 16 million people and supports a rich diversity of ecosystems and wildlife. Despite its ecological and social importance, the basin is under severe and growing pressure. The river’s flow regime has been profoundly altered over the past 130 years through extensive damming, channelisation, and water diversions. Natural flows have been depleted by 85%, and in many stretches the river now runs dry for months at a time. Agriculture is the primary driver of this depletion, accounting for roughly 85% of total water use across the basin. Invasive riparian species such as salt cedar compound these pressures by consuming large quantities of water and outcompeting native vegetation, further degrading the river’s ecological condition. The consequences are already visible: New Mexico alone has lost 71% of its reservoir storage capacity since 2002, leaving communities increasingly vulnerable to drought and unreliable water supplies.

The Rio Grande-Rio Bravo is now recognised as one of the ten most endangered rivers in the world. Without coordinated action to restore environmental flows and reduce unsustainable water consumption, the basin faces worsening water insecurity for both communities and ecosystems across the United States and Mexico.