Watersheds FAQs
What is a watershed?
A watershed is the land area that drains into a stream. Some watersheds are very small (less than one acre), while large watersheds, like the Susquehanna River watershed, may cover thousands of square miles. Any place that you stand is part of many watersheds of varying sizes.
How many watersheds are there in Pennsylvania?
Thousands of small watersheds drain into progressively larger watersheds. Pennsylvania has six major watersheds, including the Ohio River, Susquehanna River, Delaware River, Potomac River, Lake Erie, and the Genesee River.
Where does the water come from that is in a stream?
Water in a stream during dry weather comes from groundwater beneath the surface. During a rainstorm, water running over the ground surface or through shallow soil will contribute to the increasing amount of stream water.
What is groundwater?
Groundwater is water stored underneath the surface in layers of rock. The water may be stored in the pores of the rock or in cracks and fractures in the rock. Contrary to popular belief, groundwater does not ususally exist in large underground lakes or streams.
What affects the water quality of a stream?
The natural characteristics of stream water are mostly determined by the soils and bedrock geology of the watershed. Watersheds with limestone geology tend to have streams with a higher pH and more dissolved minerals. Watersheds with sandstone or shale geology usually have a lower pH and few dissolved minerals. Land use and people's activities within the watershed will further affect the stream water quality.
