Like most of the East Coast states, Virginia averages about 42 inches of rainfall a year, (that’s 12 inches more than the national average). Virginia is crisscrossed with streams and rivers and underground aquifers, each merging and converging and carrying rainfall downstream — some to the Chesapeake Bay, some to the Albemarle/Pamlico Sound in North Carolina and some even to the Gulf of Mexico.
By mapping where creeks merge into streams and streams merge into rivers we can define the boundaries of our watershed. Knowing the boundaries of your watershed will help you understand where the creeks and rivers flowing through your neighborhood have been — and where they are going. It helps you to understand what’s in the water used by every single living creature within your watershed — whether upstream or downstream of you.
Depending on where you live, your watershed may be subject to more rural sources of nonpoint source pollution (say from agricultural practices), or it may be suffering from urban sources of water pollution. By understanding your watershed, you will have the 
knowledge you need to begin controlling the water quality in your own backyard — and keeping Virginia’s waterways healthy.
