If scientists had only monitored the water more carefully, they could have prevented the Flint Water Crisis. The incident occurred because of poor water treatment and thee erosion of pipes but if they had been monitoring water then they could have solved the problem before it even happened.
In order to learn all of this they had to study the water in flint. This is hydrology. They found out that because of pipe erosion and poor water car and monitoring there was lead and other extremely harmful chemicals.
The Flint Water Crisis occurred when a new pipe was being built to make water transportation to Flint more convenient. During the construction of the new pipe, the people of Flint used the Flint River as their water source. Only then did they realize that the water didn't seem right. Turns out it was ridden with lead and other extremely harmful toxins.