Explain how clearing of land also has a detrimental impact on the water supply.

Let's say that the land has pollution meaning there is trash everywhere and dead plants over there, with those types of pollution it will harm our water supply because sometimes the pollution can affect our water.
Clearing the lands that has pollution can do good for our water and our ecosystem. When we clean the lands, more plants are able to grow, animals build their homes there, etc. That means that the animals and/or plants have a drinking water that is safe to drink and isn't polluted because we cleaned the land and the water. 
Keep America clean.

Hope this helped :)
Have a great day 

Iam pretty sure it is c. 2000 bce