Why did farmers need to develop a system to control their water supply?

just like a paragraph about it : )

Farmers needed to control the water supply because too much water or too little water would kill the crops (too much would flood the fields and too little would lead to a drought)

switch around #3 and #4

explanation:

i hope this , im not 100% on this i really hoped this

d.prevent the spread of communism outside of eastern europe.