Watershed delineation & professional map export
Find your location on the map, click where water leaves the catchment, and Terralio derives the watershed and its stream network from a 30 m elevation model — then gives you a print-ready map sheet and the GIS files behind it.
Every successful analysis produces the three things a watershed study actually needs.
Search a place, pan and zoom the map, or type coordinates. The map is the interface.
Click where water leaves the catchment. Terralio Watershed snaps the point onto the drainage network it derived from the elevation data, and tells you how far it moved.
The catchment, its streams and its metrics appear on the map. Open the export preview, adjust the sheet, and download the map and data.
The traditional route — download a DEM, fill sinks, compute flow direction and accumulation, extract the catchment and streams, style everything, then build a layout with legend, scale and north arrow — is the part Terralio Watershed removes.
Copernicus DEM GLO-30 at 30 m resolution, read on demand from the AWS Open Data archive. No dataset to download and no account. The dataset covers land worldwide — that is coverage of the elevation data, not a promise that every basin resolves at 30 m.
Depression filling with a Priority-Flood algorithm, then D8 flow direction and accumulation. The stream network you click is the same one the outlet snaps to.
Every run is checked and labelled — snapping distance, catchment plausibility, elevation coverage. Results that need a second look say so, on screen and on the exported sheet.
Source, product version, resolution, projection, method and processing date are written into the PDF, the GeoJSON and the ZIP manifest — so the map can be defended in a report.
Terralio produces an automated analysis, not a certified delineation. Knowing where it is weak is part of using it, so each result is labelled on screen and on the exported sheet rather than presented as a verdict.
Catchments with real relief, draining to a channel the 30 m elevation model resolves — headwaters, wadis and river reaches, up to basins of the order of a few thousand square kilometres.
Flat and arid terrain, dense urban areas, engineered channels, dams and reservoirs. There, the drainage a 30 m DEM can see is not always the drainage on the ground: a run may be refused, or returned for review.
The analysis window is widened upstream until the catchment closes, within a bounded computation budget. A very large basin can reach that bound — the result then states that the basin still extends past the window, instead of presenting a partial catchment as a whole one.
Check a result against your own knowledge of the site before using it for engineering, safety, regulatory, insurance or emergency decisions. Terralio is not a regulatory authority and its output is not an official delineation.
No subscription, and credits never expire. One credit pays for one new watershed delineation, with every export.
$5
10 new delineations
For occasional use
$0.50 per credit
Start with a free trial$15
40 new delineations
For recurring work
$0.38 per credit
Start with a free trialA free account with a confirmed email address includes 1 trial delineation of up to 1,000 km², one per account and per network: the watershed on the map. 1 credit pays for a new watershed delineation that succeeds and is saved, with its report, sheets and GIS files, or unlocks your trial watershed without recalculating it.
A delineation needs a signed-in account, and is charged only when it succeeds. Reopening and exporting a watershed you paid for stays free, with no credits left.
A delineation runs against your account, so signing in comes first. That is also what keeps every result you calculate, and what lets you take the work away.
Create your free account, click an outlet, and the catchment, its streams and its numbers are yours — saved, and exportable as often as you need.
Try it free