Global river datasets represent rivers that flow downstream in single paths that follow surface elevation, but they often miss branching river systems found in areas such as floodplains, canals, and deltas. Forked, or bifurcated, rivers also often exist in densely populated areas, so mapping them at scale is crucial as climate change makes flooding more severe.
Wortmann et al. aimed to fill the gaps in existing global river maps with their new Global River Topology (GRIT) network, the first branching global river network that includes bifurcations, multithreaded channels, river distributaries, and large canals. GRIT uses a new digital elevation model with improved horizonal resolution of 30 meters, 3 times finer than the resolution of previous datasets, and incorporates high-resolution satellite imagery.
The GRIT network focuses on waterways with drainage areas greater than 50 square kilometers and bifurcations on rivers wider than 30 meters. GRIT consists of both vector maps, which use vertices and pathways to display features such as river segments and catchment boundaries, and raster layers, which are made up of pixels and capture continuously varying information, such as flow accumulation and height above the river.
In total, the effort maps approximately 19.6 million kilometers of waterways, including 818,000 confluences, 67,000 bifurcations, and 31,000 outlets—6,500 of which flow into closed basins. Most of the mapped bifurcations are on inland rivers, with nearly 30,000 in Asia, more than 12,000 in North and Central America, nearly 10,000 in South America, and nearly 4,000 in Europe.
GRIT provides a more precise and comprehensive view of the shape and connectivity of river systems than did previous reference datasets, the authors say, offering potential to improve hydrological and riverine habitat modeling, flood forecasting, and water management efforts globally. (Water Resources Research, https://doi.org/10.1029/2024WR038308, 2025)
This article originally appeared in EOS Magazine.