Question

Why do humans build dams?

Answer 1

Humans build dams because theres pluming within the dam that brings the water from the river or lake to our faucets so we can have water they also stop the water from getting on the other side if them which is often a city. 
Hope this helps! 

Answer 2

Dams are important because:
They provide water for domestic, industry and irrigation purposes.

Dams often also provide hydroelectric power production and river navigation.
Domestic use includes everyday activities such as water for drinking, cooking, bathing, washing, and lawn and garden watering.
Dams and their reservoirs provide recreation areas for fishing and boating.
They help people by reducing or preventing floods. During times of excess water flow, dams store water in the reservoir; then they release water during times of low flow.