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The hydrograph above is for a river in a temperate climate. $x$ marks the lag time and $y$ marks peak discharge.

Discharge is the volume of water that passes through the channel in a given length of time. We can estimate it by:

multiplying the river velocity by the cross$-$sectional area of the channel.

multiplying the river velocity by the average depth of the channel.

multiplying the river velocity by the width of the channel.

dividing the river velocity by its depth, averaged over small increments.

dividing the river velocity by the width of the channel.