A streamflow-gauging station beside Huey Creek in Antarctica's rocky McMurdo Dry Valleys.

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Preparing the 3D view

Preparing lighting and the first complete frame…

Model scale

1 km² idealised catchment. relief, river width and vegetation enlarged. 24-hour storm view.

9.6 h · rain 0.0 mm/h · Q 0.25 m³/s · peak 0.59 m³/s · lag 3.10 h.

How to read these results

Runoff fraction 0.37; storage time 5.04 h in the selected catchment model.

Storm hydrograph

Read the main features of a storm hydrograph and explain how urban surfaces can change the timing and size of peak discharge.

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

Why it happens

A storm hydrograph shows how river discharge changes after rainfall. Infiltration, storage and routing delay the response; a greater runoff fraction can produce a higher and earlier peak.

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USGS gauging station at Huey Creek, Antarctica, 12 December 2001. Repeated measurements of stage and discharge produce a river's hydrograph.

Try a comparison

Increase Urban cover and compare peak discharge and lag time. Return to a less urban catchment and explain how infiltration and storage change the response.

Reading the result

The calculation uses an invented catchment and prescribed storm so you can compare processes without treating the curve as a local forecast.

A common misunderstanding

Peak river discharge occurs at exactly the same time as peak rainfall.

Water takes time to move through a catchment and its stores, so the discharge peak commonly follows the rainfall peak. The delay depends on rainfall location and duration, catchment size, slopes, soil conditions and drainage. State which rainfall reference is used when measuring lag time.

Cases

Process0.40Urban cover0.20Rain1.00