What happens to most of the water that falls on central Pennsylvania's Happy Valley each year (or any similar place, such as Washington, DC or other places with trees) ?

Gets absorbed by roots and soil

Explanation:

In areas that are loaded with trees the water first is absorbed by the roots and soil. The is crucial for the survival of the tree and a part of the water cycle. Water is also held in the soil as the roots act as a support for soil that is heavily water laden. Some of the water then runs down to the water table where it feeds estuaries and other watershed areas.

The largest amount of most of the water that normally falls as rain on places with many trees just like the Pennsylvania's valley every year usually gets re - evaporated into the atmosphere usually via these trees.

Then, a good quantity of the remainder of this rain, soaks down into the ground and later flows to streams and rivers through the ground.