ASTER satellite image of branching tributary valleys near the Colorado River in Canyonlands, Utah.

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Preparing the 3D view

Preparing lighting and the first complete frame…

Model scale

Idealised surface catchment. relief, channels and vegetation enlarged.

Source. The beginning of this channel. Real headwaters can be springs, wet ground, snow or glacier melt. Gold follows the surface divide; the whole enclosed land area contributes, not just the blue channel. Groundwater divides may differ.

Drainage basin

Trace water through a drainage basin and explain how the watershed connects the tributaries to a shared outlet.

Drag to rotate. Hold Ctrl and scroll to zoom, or pinch on a touch screen.

Why it happens

A drainage basin collects water that flows towards a common outlet. The watershed separates it from neighbouring basins; tributaries connect hillslope inputs to the main river.

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ASTER, 24 September 2005: tributaries dissect sandstone in Canyonlands, Utah. A drainage network collects flow towards a main river.

Try a comparison

Follow a tributary to its confluence with the main river. Hide the labels and ask a partner to locate the source, confluence and mouth.

Reading the result

The terrain is a teaching catchment, and the flow traces show routes rather than measured travel times.

A common misunderstanding

All rain falling within a drainage basin reaches its river immediately.

Rainfall can be intercepted, infiltrate soil, replenish groundwater, evaporate or enter surface runoff. These pathways have different travel times, and some water remains stored or leaves through evapotranspiration. The river’s response depends on both rainfall and the basin’s existing conditions.

Cases

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