Scientific Reports Archive
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GUNPOWDER RIVER BASIN
ENVIRONMENTAL ASSESSMENT OF STREAM CONDITIONS
CHESAPEAKE BAY AND WATERSHED PROGRAMS
MONITORING AND NON-TIDAL ASSESSMENT
CBWP-MANTA- EA-97-5
Daniel M. Boward
Helen M. Dail
Paul F. Kazyak
Maryland Department of Natural Resources
Resource Assessment Service
Monitoring and Non-Tidal Assessment Division
580 Taylor Avenue
Annapolis, Maryland 21401
December 1997
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EXECUTIVE SUMMARY
This report describes existing aquatic resource conditions during 1996 in first, second, and third order non-tidal streams in the Gunpowder River basin in Maryland.
The report also begins to assess water quality and habitat problems in the basin, as well as defining areas of high ecological quality. This information
may prove useful as watershed-specific strategies for restoring water quality in Chesapeake Bay watershed are developed and refined.
The primary source of information for this report is the Maryland Biological Stream Survey (MBSS) conducted by
Maryland Department of Natural Resources (DNR) in 1996 to characterize Maryland streams, including those within the Gunpowder River basin. Although
the primary focus of the MBSS is on acid deposition impacts, the survey is also being used for other purposes such as reporting on watershed conditions.The
MBSS is a statewide survey of first, second, and third order streams designed to characterize current biological and habitat conditions and provide a
basis for assessing future trends. The probabilistic design used for the survey, in which all streams have a known probability of being sampled,
allows for quantitative estimates of stream characteristics and conditions. This approach is not unlike taking a random sample ofvoters to determine
who is likely to win an election.
FINDINGS
Water Quality
- Acidity is not a water quality problem in Gunpowder River basin streams. All stream miles in the basin had pH greater than 6 ó the level above which most biota thrive.
- None of the stream miles in the basin had acid neutralizing capacity (ANC) less than 0 eq/L, indicating that none of the streams in the basin are chronically acidified. About 13% of the stream miles in the basin had ANC levels less than 200 eq/L and are susceptible to episodic, storm-related acidification. The remainder of the stream miles had ANC levels greater than 200 eq/L and are considered well-buffered and relatively immune to acid deposition impacts.
- None of the stream miles in the basin had summer dissolved oxygen levels lower than the state water quality criterion of 5 mg/L. This suggests that excessive loadings of oxygen-demanding organic chemicals to streams in the basin are not a problem.
- Elevated nitrogen levels (nitrate greater than 1 mg/L) occurred at all stream miles in the basin. The primary source of nitrates appear to be agriculture, but urban runoff and acid deposition are also likely contributors.
Physical Habitat
- Twenty-four percent of the stream miles in the basin had either poor or very poor instream physical habitat scores ó the amount and diversity of stable materials such as riffles, logs, undercut banks, and snags. Causes of degraded habitat include channelization, sedimentation, and riparian zone deforestation.
- Almost 30% of the stream miles in the basin had unstable stream banks, while only 2% of the stream miles had stable banks. Eroding stream banks may be an important source of sediment and nutrients to the 2 drinking water reservoirs in the basin (Prettyboy and Loch Raven), the Gunpowder River estuary, and to the Chesapeake Bay.
- In general, riparian zones along streams in the basin were in fair condition. About 50% of all stream miles had vegetated riparian zones greater than 50 meters wide, but about 15% of the stream miles contained no buffers. Forest was the dominant vegetation type in riparian zones greater than 6 meters wide. Forty-five percent of the stream miles were well-shaded.
Fish
- A total of 40 fish species were collected in the basin, including 5 gamefish: largemouth and smallmouth bass, rainbow trout, brown trout, and brook trout. With a population estimate of 66,000 individuals, brook trout were the most abundant gamefish collected. None of the fish species collected are listed as threatened, rare, or endangered in Maryland.
- About 3.2 million fish live in non-tidal streams in the basin. The most abundant fish species in the basin was the blacknose dace, a pollution-tolerant species, estimated at more than 900,000 individuals.
- Only two species of migratory fish, sea lamprey and American eel, were found in the non-tidal streams of the basin. Of these, American eels were the most abundant, with an estimated population of 56,000 individuals. One reason for the relatively low numbers of migratory fish in the basin is the 23 known barriers to fish migration which restrict upstream movements. American eels can climb over many barriers in the Gunpowder River basin that are impassable to other migratory fish.
- About 75% of the fish species collected in 1996 are native to the Chesapeake Bay drainage. Many non-native species were introduced to provide recreational fishing opportunities.
- Based on DNR's Index of Biotic Integrity for fish, about 56% of the stream miles in the basin were in either good or fair condition, while none were in very poor condition. Most good sites were in the northern third of the basin.
- With forest clearing and other human-related landscape alterations, summer stream temperatures in the Gunpowder River basin have most likely increased along with nutrient levels. As a result, brook trout populations have probably declined and were found at only 8 of the 45 sites sampled.
Benthic Macroinvertebrates
- Based on the Hilsenhoff Biotic Index, nearly 70% of all stream miles in the basin were assessed as good, while the remaining 30% were assessed as fair. No stream miles were assessed as poor using this index.
- Forty-eight of the 123 stream-dwelling benthic macroinvertebrate families found in Maryland were collected in the Gunpowder River basin. Dominant types were non-biting midges (true flies), mayflies and caddisflies.
Freshwater Mussels
- Freshwater mussels were observed at only 2 of the 45 sites sampled in the basin. Eastern elliptio (Elliptio complanata) and the Asiatic clam (Corbicula fluminea) were the only 2 species collected in the basin.
Reptiles and Amphibians
- Reptiles and amphibians were present at 91% of the sites sampled in the basin. A total of 13 species of frogs, toads, turtles, salamanders, and snakes were observed.
Summary
- The major impacts to non-tidal streams in the basin appear to be nitrogen enrichment, streambank instability, high riffle embeddedness, and loss of forested riparian zones. The most likely reasons for these impacts are stream alterations resulting from agricultural activities and urban sprawl, especially in the southern part of the basin.
The full version of this report is not currently available to download. To request hard copies, please contact:
Daniel M. Boward
Maryland Department of Natural Resources
Ecological Assessment Program
Monitoring and Non-Tidal Assessment Division
Resource Assessment Administration
Tawes State Office Building, C-2
Annapolis, MD 21401
dboward@dnr.state.md.us
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