Stream and River Quality TODAY

Historically, western streams and rivers were “badly polluted” (Ortman 1909 in Criswell 2002), with some noted to “run black like ink.”  In eastern Pennsylvania, streams and rivers were also polluted with the Delaware River reportedly anoxic for four months of the year, polluted with municipal waste and acidic mine output (Criswell 2002).   Some improvement to streams occurred during the late 1970s and 1980s, with some fish populations improving in response (Criswell 2002; Cooper 1983).   Although some streams have recovered from industrial impacts as rehabilitation continues across the state, one-third of all Pennsylvania water bodies still fall well below Clean Water Act standards (Penn Future 2001). 

An in-depth stream assessment conducted through most of Pennsylvania by EPA using a systematic statistical sampling during 1993 and 1994 revealed that 27% of streams were in poor condition based on fish and insect populations (Mid-Atlantic Highlands Stream Assessment 2000).  Most first, second and third order streams were evaluated for the state during this assessment excluding streams located the southeastern region of Piedmont and Coastal Plain eco-regions.   Reference sites were found that had pristine conditions and high biotic integrity and all streams were compared to these sites to develop an index to biotic integrity based on fish and on insect abundance and diversity (EPA 2000).

Good quality stream habitat for insects was found for 25% of stream miles and good habitat for fishes was found in 14% of the Pennsylvania stream miles tested (in 1993, 1994).  However, 40% of stream miles showed poor or worse biotic integrity for fishes and poor integrity of aquatic insects was found for 25% of stream miles in Pennsylvania.   EPA studies show riparian habitat alteration and channel sedimentation were a problem on 21 and 19% of stream miles respectively, suggesting that development and alteration of riparian habitats continue to be huge threat to state streams and rivers.   Mine drainage, acidic deposition or contaminants were a problem in 15% of stream miles.    Nutrient and runoff pollution in 10% of stream miles and non-native fishes were found in 44% of stream miles.

Figure 53.   DEP stream sampling showing proportion of drainage impaired across Pennsylvania (DEP 305b reports).

The state of Pennsylvania has conducted its own sampling of many streams within the state, testing approximately 60% of state streams.   DEP sampling focuses primarily on chemical quality of the water.   The DEP stream sampling shows that 18% of stream miles sampled  state-wide were impaired (Figure 53).  The ten river watersheds sampled by DEP show between 4 and 43% of the river miles in the state are impaired.   The difference as compared to EPA results may be the difference in how each sampling regime defined impairment or high quality, and slightly different sampling approach (e.g., the EPA sampled all first, second, third order streams, but excluded southeastern region; DEP sampled across the state but has only sampled approximately half of the stream and river miles statewide (see map, Figure 56).  

DEP sampling of Pennsylvania streams suggests that impairment is primarily caused by agricultural runoff (2,900 stream miles), mine drainage, and urban runoff.  

Figure 54.  Source of stream degradation in DEP stream sampling.

Figure 55.  Proportion of pollutants in Pennsylvania streams.

Non-native fishes were found in over 40% of the streams.   Pollution found in streams included primarily siltation, metals, nutrients, and acidification during DEP sampling.   Sampling by river watersheds shows that western rivers and segments of the Susquahanna and Delaware rivers show the highest rates of impairment (Figure 53).

Watershed quality is directly related to proportion of forest cover remaining.   Most watersheds in Pennsylvania are primarily forested (Jones et al.  1997).   Between 1970 and 1990, population density increased regionally by a median of 10 persons per square kilometer.    Watersheds in southeast and eastern Pocono regions showed from 18 to 38 percent increase in population density, while many western watersheds held stable.  

Soil erosion is a significant source of stream sedimentation.   Proportion of watershed area with urban or agriculture land cover exceeds 50% in all southeastern watersheds and much of far northwestern watersheds (Jones et al.1997).   The only watersheds with less than 17% human altered landscapes occur in north-central and some northeastern watersheds.   Road density is highest in regions near metropolitan areas of Philadelphia and Pittsburgh, suggesting these watersheds may be affected more extensively by road runoff.

Acid mine drainage was a significant stressor to streams in both EPA and DEP sampling.   Pennsylvania DEP sampling suggests that nearly 10% of stream miles are degraded or imperiled.   EPA sampling suggests stream degradation caused by riparian habitat loss, degradation for 21% of stream miles and channelization for 19%.   Mine drainage, acidic deposition, and contaminants in fish tissue were associated with 15% of PA stream miles (EPA 2000).  Pollutants such as nitrogen and phosphorus were found in 10% of stream miles.    Non-native fishes were found in 44% to 47% of stream miles (DEP, EPA respectively).  Interestingly, sampling in West Virginia shows much lower proportion of streams with non-native fishes (22%), and lower fish tissue contamination (1% in West Virginia vs.  15% in Pennsylvania (EPA 2000).

Soil erosion primarily from agriculture, is a significant source of stream sedimentation.   The proportion of watershed area where soil erosion exceeds the threshold of one ton per acre per year ranges from 1% to 35% of watershed area.   Most of the southeastern and southwestern watersheds have 24% of their area showing soil erosion above threshold values (Jones et al.1997).    Soil erosion increases on steep slopes when vegetation is removed.   Vegetation loss from 1975 to 1990 was seen on slopes greater than 3% in south central and eastern Pennsylvania and a few other scattered watersheds (Jones et al.  1997).

Precipitation is measured at sampling stations across the state through a cooperative DEP and Pennsylvania State University study.   In 2000, weekly samples were collected and analysed for acidity and pollutants.   The mean annual pH for the state was 4.30 which is more acidic than measures in 1999, but less acidic than 1980s measurements by 34%.  Pennsylvania precipitation ranges from 17 to 25 times more acidic than uncontaminated precipitation would be currently.  Reductions of acidity found in recent years are assumed to be the result of reduced air emissions from industrial sources following implementation of Clean Air Act.    Despite the reductions, the state still has the most acidic precipitation of any region in North America (Lynch et al.  2001).   There are 6500 miles of state streams that are too acidic to support trout.   A large number of streams, 3,000 in 45 counties, have been impacted by acid mine drainage (DEP, Figure 56, 57).   The Pennsylvania Fish and Boat Commission reports that one-third of the stocked trout streams in the state are vulnerable to acidification due to low alkalinity values, or buffering capability (www.fish.state.pa.us).   Many sport fishes are contaminated with mercury and PCBs from industrial runoff or Lake Erie contaminated sediments (PennFuture 2001).   Runoff and degradation of streams in farmland continues, as does increasing landscaping chemicals.   Pennsylvania ranks in top ten most polluted states for sulfur dioxide and nitrogen dioxide pollution, partly due to air pollution received from outside the borders and partly from industrial uses within the state.  

Acidic deposition can reduce diversity of invertebrates, amphibian and reptile breeding success, and fish abundance and diversity.   Crustacean species are particularly sensitive to water quality.  Fish can be stressed by acidic waters by upsetting their chemical balance, and toxic metals can be leached into water affecting fish survival and survival of eggs and young.   Different areas of the state may respond differently to acidic deposition, with some waterways being better able to buffer or neutralize acidic input.   A large proportion of Pennsylvania streams are affected by acidic conditions (Figure 56, 57).

Click on image for full-size map

Figure 56.   Stream quality in Pennsylvania, red indicates degraded streams, green undegraded, and gray unassessed (DEP).

Figure 57.   PA Streams affected by acidic mine drainage and deposition (from EPA 2000).