Why is the variation of water flow every year a problem?

The vast majority of rivers are known to exhibit considerable variability in flow over time because inputs from the watershed, in the form of rain events, snowmelt, groundwater seepage, etc., vary over time.

Explanation:

true. earthquakes are felt whenever there is a slip around a fault in the rocks below the earth. this reorientation of faults create sesmic waves and is known as earthquake, the severity of which is measured in richter scale. these are more prominent in hilly regions as the rocks usually form faults to balance the pressures on it.

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