Understanding a Hydrograph
The hydrograph is used to show how a river responds to the amount
of rainfall in the catchment area of the river.
A hydrograph is a graph used by the Environment Agency to show
the amount of water in a river and the amount of rainfall that has
fallen. The hydrograph shows the maximum level of the river before
it starts to overflow its banks. By comparing the rainfall and the
water levels predictions may be made about the likely flooding problems.
Rainfall takes time to seep into the streams and rivers because
of many factors (Link to Water Volume)
and the hydrograph shows the effect of the delay.
The graph shows that the water level peaks 4 hours after the rain
begins. The water level then declines less stepply than it rose,
and falls back to where it was before the rainsfall occurred - after
about 12 hours.
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