Home** Our Work **Programs**Monitoring & Protection** Susquehanna River Subbasin Surveys

# Susquehanna River Subbasin Surveys

The Commission’s Subbasin Survey program was established in themid-1980s through funding from the U.S. Environmental ProtectionAgency. The six major subbasins are surveyed on a rotating basisto provide a broad assessment of aquatic communities, instreamhabitat, and water quality within each subbasin.

### Study Design

Susquehanna River Subbasins
Earlier iterations of the Subbasin Survey program primarily targetedconvenient access points on major tributaries. Oftentimes, sites thatprovide easy entry from a bridge or roadway are also subject torunoff, erosion, and/or channel alteration, which can negativelyimpact local habitat andwater quality.Data from targeted sites therefore represent localized conditions andcannot be extrapolated to conditions across the entire subbasin.

In 2014, theCommissionbegan utilizing a spatially balancedprobability design to select sites for the Subbasin Survey program.Each year, 20 new sites are randomly chosen from the focus subbasinusing the Generalized Random Tessellation Stratified (GRTS) algorithmin the spsurvey R package (Dumelle and others, 2023). The GRTSalgorithm produces a representative sample of sites accuratelyreflecting the spatial distribution of streams across the subbasinbased on stream order andecoregion.The resulting dataset from randomly chosen sites will allow theCommission to make inferences about conditions within each subbasin,as well as in the basin as a whole.

### Types of Data Collected

###### Biological Communities

Aquatic organisms can be viewed as living indicators of stream healthand the long-term effects of ecosystem stress. Many state and federalagencies have developed indices of biological integrity based onbenthic macroinvertebrate communities.Benthic macroinvertebratesare organisms that live on the stream bottom,including aquatic insects, crayfish, snails, bivalves, and worms.Sensitivity to environmental degradation varies among different typesof macroinvertebrates, making them ideal biological indicators. TheCommission utilizes the Pennsylvania Department of EnvironmentalProtection’s (PADEP’s) protocols for sampling the benthicmacroinvertebrate community.

###### Habitat

Physical habitat conditions impact the ability of a stream to supporta healthy biological community. Factors such as substrate composition,velocity-depth regimes, bank stability, and riparian vegetationdetermine whether or not a stream reach is suitable for particularfish species or macroinvertebrates. The physical habitat at SubbasinSurvey sites is assessed using a modified version of the U.S.Environmental Protection Agency’s (USEPA’s) Rapid BioassessmentProtocol (RBP) (Barbour and others, 1999).

###### Water Quality

Water quality monitoring dataare used by state and federalregulatory agencies to identify current and emerging problems withcontaminants, and to determine compliance with drinking water,recreational use, and aquatic life standards. The Commissionmeasures temperature, dissolved oxygen, pH, specific conductivity,and turbidity in the field using handheld meters. Water samples arealso sent to a lab to be analyzed for the following parameters:alkalinity, aluminum, calcium, chloride, iron, magnesium, manganese,nitrate, phosphorus, potassium, sodium, sulfate, total dissolvedsolids, and total organic carbon.

### Site Ratings

Each Subbasin Survey site receives condition ratings of excellent,good, fair, poor, or very poor for biological conditions, habitat,and water quality based on the numeric IBI, RBP, andWQI scores.Table 1 summarizes the scoring ranges and corresponding conditioncategories for each index.

PADEP’s Benthic Index of Biotic Integrity for Freestone WadeableStreams (IBI) is used to assess the biological community (PADEP, 2013).The IBI incorporates scores from six individual metrics into a singleindex score with values ranging from 0 to 100.

Physical habitat is categorized based on 11 physical streamcharacteristics pertaining to substrate, pool and riffle composition,shape of the channel, conditions of the banks, and the riparian zoneon a scale of 0 - 20 (20 being optimal). These 11 scores are addedtogether to produce a total RBP habitat score ranging from 0 to 220.

***Table 1. Index of Biological Integrity (IBI), Rapid BioassessmentProtocol (RBP), and Water Quality Index (WQI) Scoring Ranges forCondition Category Ratings***

The Commission’sSusquehanna River Basin Water Quality Index (WQI)is used to evaluate water quality conditions. The WQI produces threeseparate category scores for metals, nutrient enrichment, anddevelopment, which are then averaged to produce an overall waterquality score between 0 and 100.

### Subbasin Survey Dashboard

Subbasin Survey Dashboard

Susquehanna Subbasin Survey Dashboard

###### References

Barbour, M.T., J. Gerritsen, B.D. Snyder, and J.B. Stribling. 1999.Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers:Periphyton, Benthic Macroinvertebrates, and Fish, Second Edition. EPA841-B-99-002. U.S. Environmental Protection Agency, Office of Water,Washington, D.C.

Dumelle, M., T. Kincaid, A.R. Olsen, and M. Weber. 2023. spsurvey:Spatial Sampling Design and Analysis in R. Journal of StatisticalSoftware 105(3):1-29. (doi:10.18637/jss.v105.i03)

Pennsylvania Department of Environmental Protection (PADEP). 2013.An Index of Biotic Integrity for Benthic Macroinvertebrate Communitiesin Pennsylvania’s Wadeable, Freestone, Riffle Run Streams.https://www.dep.pa.gov/Business/Water/CleanWater/WaterQuality/Pages/Macroinvertebrates.aspx