Forests and Water Belong Together

Posted: February 26, 2019

In Pennsylvania, forests serve many functions that affect both water quantity and quality.

Forests and water are inextricably coupled. In Pennsylvania, forests serve many functions that affect both water quantity and quality. Forest soils are especially good at allowing rain and snow melt to move into the soil. This infiltrating water is necessary for recharging subsurface aquifers essential for drinking water supplies. Forest canopies capture, depending on the season, up to 40 percent of rain water and allow it to evaporate back into the atmosphere; thus, helping to mitigate stormwater impacts. And just as we enjoy the shady forests, so do streams, which flow cooler under leafy forest canopies.

The surface waters that flow across our state, as well as our below ground aquifers, belong to us all – they represent the waters of the commonwealth. Our state’s Clean Stream Law (P.L. 1987) describes the "Waters of the Commonwealth" as including any and all rivers, streams, creeks, rivulets, impoundments, ditches, water courses, storm sewers, lakes, dammed water, ponds, springs and all other bodies or channels of conveyance of surface and underground water, or parts thereof, whether natural or artificial, within or on the boundaries of this Commonwealth.

Rivers, streams, springs, ponds, and lakes are common across Pennsylvania’s landscape. You may not know that Pennsylvania’s 86,000 miles of rivers and streams ranks it 18th among the states. Considered a different way, Pennsylvania ranks first in the ratio of miles of streams to land area at 1.8. That is nearly 2 miles of surface water flow in every square mile of land! (To learn more about this statistic, visit The Klaber Group report).

Clearly, Pennsylvania is a water rich state. We have water for communities, agriculture, industry, and recreation; however, the past couple of years have seen times when we have had too much water. This past summer, in some parts of the state, rainy days seemingly outnumbered sunny ones. Both rain volume and intensity were above average. And, this winter, we’ve had both snow and rain interchangeably.

Protecting and managing our above and below ground water resources is both a right and responsibility. Every person living and working in Pennsylvania is responsible for protecting water quantity and quality. If you own, manage, or use land, especially forest, the duty to maintain water quality is even higher as much of the water flowing through forested land carries official designations of high value or exceptional quality. This only emphasizes the importance of forest cover to water quality.

In the context of forests and water quality, sediment pollution is one of the most threatening types of pollution. The movement of soil particles into water is the result of soil erosion. Lacking surface disturbance, annual accumulation of leaves and other naturally occurring forest litter protects the underlying soil from rain impact and encourages water infiltration. Anything that disturbs this important soil cover, whether it is logging equipment, ATVs, horses, or even hikers, increases the risk of soil movement, and that sediment can enter streams, wetlands, and other water bodies. Sediment pollution reduces water clarity, affects all aquatic insect, amphibian, and fish life cycles, and can adversely increase water nutrient levels. Reducing sediment pollution is critical to water health.

Take a few minutes and consider how you use forests and how you may witness your impacts on water quality, both large and small. As we extract forest products or harvest trees from forests, there are obvious risks that the resulting “earth disturbance” from skidding and moving logs with heavy machinery will create muddy conditions. Without the use of recognized “best management practices” (BMPs) to protect forest sites and water quality, logging would might be a major problem affecting water quality; however, the logging industry has a very good record for protecting the waters of the commonwealth. (To learn more about BMPs, review or download the publication).

Less obvious impacts on water quality are some recreational activities such as off-road vehicle and all terrain vehicle (ATV) use. Poorly designed riding trails, which often occur without purposeful design considerations and involve frequent stream crossings, can impact streams and wetlands in private woodlands. While the overall amount of disturbed area may seem small compared to a timber harvesting operation, the proximity to streams and involvement of steep slopes can elevate impacts.

As noted earlier, over the past couple of years Pennsylvania has experienced increased rainfall and, in some areas, forest soils struggle to accommodate the volume and intensity of rain events. When poorly designed, constructed, and maintained roads, trails, and stream crossings occur, whether they involve timber harvesting or recreational use, the risks to water quality increase. It behooves us all to protect valuable water resources and to learn how we can protect and ensure adequate water for our future.

"When the well's dry, we know the worth of water."
- Benjamin Franklin, (1706-1790), Poor Richard's Almanac.

Contact Information

James Finley, Ph.D.
  • Professor Emeritus of Forest Resources
Phone: 814-863-0402