Why are so many big cities located along the banks of a river?

Explanation:

Maritime trade or water transport is the cheapest and safest mode of transport and hence it eases trade between two points ensuring the goods remain affordable to the end consumers.

Besides, proximity to water source ensures that the residents of the cities access clean water at reduced costs.

it should be p1 v1 = p2 v2

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.