Acid Precipitation

Note: This is a text-only file of a Fish & Boat Commission publication that includes graphics and a map. Contact the Commission if you'd like a free copy of this complete publication. 

Pennsylvania is blessed with thousands of miles of freshwater streams ranging from high mountain headwater tributaries to the slower-moving lowland varieties. All are affected to some degree by acid deposition. The purpose of this brochure is to acquaint the reader with the causes, effects and the need to reduce its effect on our aquatic environment. "The creek is a symbol of our greatest resource; as the creek flows, so flows mankind."

During the past couple of decades, thousands of scientific reports have documented the serious effects of acid deposition in North America and Europe. The control of the air pollutants that cause acid rain and deposition has become a battle cry for conservation-minded citizens in many industrialized countries. Because Pennsylvania waters receive the highest amount of acid deposition of any state in the nation, the Pennsylvania Fish and Boat Commission is particularly concerned about this problem.

Acid deposition is primarily the result of human-made emissions from burning fossil fuel, automotive exhausts and other industrial processes, which emit sulfur dioxide (SO2) and nitrogen oxide (NOx) gases. These pollutants are transported in the atmosphere, chemically transformed, and deposited either as wet deposition (such as rain, sleet or snow) or in the form of sulfuric and nitric acids, or as dry deposition in the form of sulfate and nitrate particles. This deposition has been shown to have adverse effects on streams, lakes, forests, buildings, drinking water and human health.

Pennsylvania receives the most acid deposition of any state in the nation because, in addition to being the third highest producer of the gases that cause acid deposition, we are also located downwind from the highest concentration of air pollution emitters. Monitoring stations located throughout the Commonwealth reveal that the pH of our rainfall averages an incredible 4.0 to 4.1, which is many times more acidic than unpolluted rain.

Different areas of the state may respond differently to acid deposition, depending on the region's natural ability to "buffer" or neutralize the incoming acidity. This ability of a body of water to neutralize acids is called its "acid neutralizing capacity," and depends on the dissolved mineral content in the water, which, in turn, depends on the composition of the soils and bedrock in the watershed. If the watershed is primarily underlain by sandstone or igneous rocks such as granite or basalt, then the streams and lakes in the region will have low acid-neutralizing capacity. If soils and waters of an area continually receive acid deposition, their neutralizing capacity will decrease. With little or no neutralizing capacity, the water will gradually acidify and fish and other aquatic life forms will be adversely affected.

The acid-neutralizing capacity of a waterway is measured by a test called alkalinity, which can be expressed as milligrams per liter (mg/l), or parts per million (ppm) of calcium carbonate. According to international standards, streams and lakes are considered vulnerable to acid deposition if base flow alkalinity values are 10 mg/l or less. These waters are especially susceptible to effects of the continued influx of atmospheric acids. Using this criterion, about one-third of the 4,800+ miles of stocked trout streams in Pennsylvania are considered vulnerable. These streams are indicated on the accompanying map and county lists. In addition to the stocked trout streams on the map, there are even more miles of unstocked waters throughout the Commonwealth that are vulnerable to acid deposition. Some of these vulnerable waters in Pennsylvania are lakes, but most are high-quality small, mountain streams that support naturally reproducing trout populations.

What is the effect of acidification on vulnerable streams and lakes? As a waterway becomes acidified, algae and rooted aquatic plants die off, reducing the available food supply for aquatic insects and fish. Healthy aquatic insect communities are replaced by acid-tolerant individuals, which are not as desirable or abundant a food supply for higher organisms such as certain species of fish. More tolerant fish species may begin to replace the original populations, or the fish may disappear entirely from a waterway.

Fish populations can also be directly affected in several ways. Acidity can stress a fish's basic body function, because it upsets the fish's ability to regulate its blood chemistry. Toxic metals, such as aluminum, can be leached from the soils and delivered to the lakes and streams by acidic rainfall. For example, small amounts of dissolved aluminum can cause mortality in fish by damaging their gills and decreasing sodium in their bloodstream. Finally, fish eggs and fry are very susceptible to high acidity and toxic metals. Partial or entire year classes can perish, leaving older, more resistant individuals to maintain a remnant population.

Over the years, the Fish and Boat Commission has been forced to change many of its stocking patterns on streams receiving increased acidity from acid deposition. In the beginning stages of acidification, it might be possible to change a stocking pattern simply by using a different species of fish. For example, one pattern change may be to change from the stocking of acid-sensitive rainbow trout to the more acid-tolerant brook trout. Another strategy is to change stocking schedules, so that the sensitive fish are not stocked preseason, when the heavy spring rains and winter snowmelt increase the acid and aluminum content of the streams.

Finally, the Fish and Boat Commission may be forced to discontinue stocking altogether when even the brook trout cannot live in the acid runoff. A review of the stocking records in Pennsylvania indicates that since the late 1950s, more than 90 streams have been subject to trout stocking management changes as a result of increasing acidity. Since 1969, the Fish and Boat Commission has had to remove 18 waterways from the trout stocking list, because of degraded water quality caused by increasing acidity and toxic aluminum.

Currently Fish and Boat Commission managers test water samples from known vulnerable streams every year during March and April. To make future management decisions, fisheries management personnel have also conducted studies on the chemical characteristics and survivability of trout stocked in sensitive water.

Numerous government and university studies have also been conducted in Pennsylvania. Studies conducted by the U.S. Environmental Protection Agency indicate that the Pocono lakes region is the second most negatively affected lakes region in the country. A Lehigh University study determined that out of 160 lakes in the Pocono region for which there were data, 70 percent were sensitive to acid deposition and 8 percent were already acidified. Scientists from the Pennsylvania State University and from California University of Pennsylvania conducted many watershed studies on the Laurel Hill Ridge, which contains the majority of the natural trout streams in southwestern Pennsylvania. One of their studies revealed that 10 of the 61 watershed samples were fishless and concluded that "26 percent of the headwater streams on the Laurel Hill are severely impacted by acidification episodes." The National Academy of Science has stated that protection or recovery would occur on 80 percent of the nation's affected waters if sulfate deposition were reduced to 17 kg/ha/year (15 pounds/acre/year). In Pennsylvania, sulfate deposition ranges from 25 to 45 kg/ha/year (23 to 41 pounds/acre/year), so a reduction of approximately 50 percent would be required.

The Pennsylvania Fish and Boat Commission has actively sought legislation to control acid deposition since 1978. Our 1986 "Policy on Acid Precipitation" urged the federal and state governments to reduce SO2 and NOx emissions by 50 percent. After 13 years of study, deliberation and hearings, Congress approved the Clean Air Act Amendments of 1990. Many provisions including acid deposition were new to the Clean Air Act. One of the goals of the acid deposition provision is to reduce annual SO2 emissions by 10 million tons/year from the 1980 emission levels and cap the annual utility SO2 emission rate at approximately 8.9 million tons by the year 2010. Another important goal of the provision is to reduce annual NOx levels by two million tons from the 1980 levels, but unfortunately no caps were put in place. The Congressional findings and passage of the Clean Air Act Amendments were historic in a sense that the long debate about the cause and effect of acid rain was ended.

The Pennsylvania Fish and Boat Commission was pleased that Congress finally passed the necessary legislation that will hopefully end the acid rain crisis. Scientists are optimistic that the 1990 Amendments will benefit Pennsylvania's affected waterways. A National Acid Precipitation Assessment Program (NAPAP) report speculates that because the major emission sources are located along the Ohio River Valley, Pennsylvania should experience a reduction of SO2 emissions by greater than 50 percent and a SO2 deposition rate of less than 17 kg/ha/year. Although NAPAP will continue to monitor deposition rates and test water quality, we will not know the final results of the Clean Air Act Amendments until the year 2010.

The passage of the 1990 Amendments is a credit to all the concerned anglers, citizens and scientists who took the time to voice their opinions for cleaner air. However, our work is not done. Attempts will continuously be made to weaken the current legislation. We all must remind our Congressional leaders that acid deposition is still a major concern and that complete enforcement of the 1990 regulations is a must. We can also do our part to limit air pollution by conserving energy, promoting mass transit and supporting strict automobile emission inspections. Future generations of Pennsylvanians are counting on us to protect, conserve and enhance the water resources of our state.

Acid Activity

Many people not familiar with chemistry have a hard time understanding the pH scale. The scale represents the potential hydrogen ion activity of a water environment and therefore its relative corroding action. Although the scale contains 15 numbers (0 to 14), the acid activity at a pH of 7 and above is not very significant. Numbers below a pH of 7 represent increased acid activity and potential harm to the environment. Most organisms live in environments where the pH ranges between 6 and 9. At pH levels below 4.5, the acid activity is too toxic for most organisms to survive.

A pH number is a negative logarithm, so the number is a decimal part of a whole number. A change from one whole pH number to another represents a tenfold increase or decrease in the acid potential of a water environment. The chart above shows several ways to present the concept of acid potential (pH) and some pH levels for common liquids in our environment.

Although all Pennsylvania waters receive acid deposition, the locations of the most vulnerable streams are directly related to the geology and physical features of the state. By comparing the larger map above with the smaller one to the right, it becomes apparent that most of our vulnerable streams are located in the sandstone mountainous regions of Pennsylvania.

Stocked trout streams vulnerable to further acidification

Antietam Creek, E. Br.
Carbaugh Run
Conococheague Creek
Marsh Creek, Little
Middle Creek

Huling Run

Bobs Creek
Cove Creek
Maple Run
Wills Creek

Northkill Creek
Pine Creek

Bobs Creek Vanscoyock Run

Millstone Creek
Schrader Creek
Schrader Creek, Little

Bens Creek
Killbuck Run
Laurel Run

Clear Creek
Hicks Run, E. Br.
Hicks Run, W. Br.
Jerry Run, Upper
Mix Run
West Creek
Wykoff Run

Bear Creek, Big
Drakes Creek
Fourth Run
Mahoning Creek
Mauch Chunk Creek
Pohopoco Creek
Sand Spring Run
Stony Creek

Beech Creek, S. Fk.
Black Bear Run
Black Moshannon Creek
Cold Stream Run
Eddy Lick Run
Fishing Creek, Little
Laurel Run
Mountain Branch
Pine Creek
Poe Creek
Sinking Creek
Six Mile Run
Wallace Run
White Deer Creek
Wolf Run

Cathers Run
Toms Run

Anderson Creek
Beech Run
Curry Run
Jack Dent Branch
Medix Run
Sawmill Run
South Witmer Run

Baker Run
Cooks Run
Hyner Run
Hyner Run, L. Br.
Hyner Run, R. Br.
Long Run
Rauchtown Creek
Young Womans Creek
Young Womans Creek, L. Br.

Briar Creek
Roaring Creek
Scotch Run
West Creek

Mountain Creek
Old Town Run

Clarks Creek
Pine Creek
Powell Creek
Powell Creek, N. Fk.
Powell Creek, S. Fk.
Rattling Creek
Rattling Creek, E. Br.
Rattling Creek, W. Br.
Stony Creek
Wiconisco Creek

Bear Creek
Bear Run
Belmouth Run
Big Run
Boggy Run
Byrnes Run
Clarion River, E. Br.
Clarion River, W. Br.
Middle Fork
Millstone Creek, E. Br.
Mill Creek, Big
Powers Run
Spring Creek, E. Br.
Straight Creek
Straight Creek, S. Fk.
Wolf Run

Chaney Run
Dunbar Creek
Meadow Run
Mill Run, Indian Ck. trib.
Mill Run, Sandy Ck. trib.
Sandy Creek, Big
Youghiogheny River (Tailrace)

Beaver Run
Bluejay Creek
Coon Creek, Little
Hickory Creek, E.
Maple Creek
Ross Run
Salmon Creek
Spring Creek
The Branch
Tionesta Creek, S. Br.
Toms Run

Aughwick Creek, Little, S. Br.
Brush Creek
Brush Creek, Little
Laurel Fork
Roaring Run, Lt. Brush trib.
Sideling Hill Creek

Garner Run
Globe Run
Laurel Run
Standing Stone Creek

Brush Creek
Cush Creek
Laurel Run
Toms Run
Yellow Creek
Yellow Creek, Little

Callen Run
Clear Run
Five Mile Run
Horm Run
Mahoning Creek, E. Br.
Mill Creek, Little
Pekin Run
Rattlesnake Creek
Sandy Creek, Little

East Licking Creek
Lost Creek

Lackawanna River
Lehigh River
Roaring Brook
Spring Brook

Stony Creek
Trout Run

Kitchen Creek
Lehigh River
Nescopeck Creek
Pine Creek
Wapwallopen Creek
Wrights Creek

Bear Creek, Little
Black Hole Creek
Hoagland Run
Larry's Creek
Loyalsock Creek
Mill Creek
Pine Bottom Run, Upper
Pleasant Stream
Rock Run
Trout Run
Wallis Run
White Deer Hole Creek

Brewer Run
Chappel Fork
Havens Run
Kinzua Creek
Meade Run
Potato Creek
Sevenmile Run
Skinner Creek
Sugar Run, N. Br.
Tionesta Creek, E. Br.
Tunungwant Creek, E. Br.
Two Mile Run

Havice Creek
Honey Creek
Lingle Creek
Treaster Run

Appenzell Creek
Brodhead Creek
Bushkill Creek
Dotters Creek
Pocono Creek
Pohopoco Creek
Princess Run
Tobyhanna Creek

Mahantango Creek
Roaring Creek, S. Br.
Schwaben Creek

Bull Run
Fowler Hollow Run
McCabe Run
Shaeffer Run
Sherman Creek

Bushkill Creek, Little
Decker Brook
Lackawaxen River
Middle Branch Creek
Saw Creek
Shohola Creek

Fishing Creek
Fishing Creek, W. Br.
Freeman Run
Kettle Creek
Lyman Run
Pine Creek, W. Br.
Sinnemahoning Creek, E. Fk.
South Woods Branch

Bear Creek
Catawissa Creek, Little
Deep Creek
Locust Creek
Mahantango Creek
Pine Creek, Schuylkill trib.
Pine Creek, Mahantango trib.
Red Creek

Kern Run
Middle Creek, N. Br.
Swift Run

Beaverdam Run
Bens Creek, S. Fk.
Blue Hole Creek
Breastwork Run
Brush Creek
Clear Shade Creek
Cub Run
Elk Lick Creek
Fall Creek
Flaugherty Creek
Glade Run
Kimberly Run
McClintock Run
Miller Run
Piney Creek
Piney Creek, Little
Piney Run
Shaffers Run
Tub Mill Run
Whites Creek
Wills Creek

Double Run
Fishing Creek, W. Br.
Loyalsock Creek
Mill Creek
Pole Bridge Run
Rock Run

Asaph Run
Asaph Run, Left

Buffalo Creek
Buffalo Creek, N. Br.
Laurel Run
Rapid Run
Spruce Run
White Deer Creek

Pithole Creek
Pithole Creek, West

Browns Run
Farnsworth Branch
Fourmile Run
Hemlock Run
Hickory Creek, East
Hickory Creek, West
Perry McGee Run
Reynolds Run
Thompson Run
Tidioute Creek
Tionesta Creek, E. Br.
Tionesta Creek, W. Br.

Lackawanna River
Lackawaxen River, W. Br.
Rose Pond Brook
Wallenpaupack Creek, W. Br.

Indian Creek
Linn Run
Mill Creek
Roaring Run
Shannon Run
Tubmill Creek

Bowman Creek
Mehoopany Creek

Your purchase of fishing equipment and motor boat fuels supports wildlife and sport fish restoration and boating access facilities. The Pennsylvania Fish and Boat Commission receives federal aid in sport fish restoration. Under appropriate federal acts, the U. S. Department of the Interior prohibits discrimination on the basis of race, color, national origin, age, sex or disability. If you believe that you have been discriminated against in any program, activity or facility as described above, or if you desire more information, please write to: The Office of Equal Opportunity, Department of the Interior, Washington, DC 20240. 



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