Large River Surveys
Background
The Commission has been monitoring the larger river systems of the Susquehanna River Basin since the early 2000s. The focus of these surveys has varied over the years based on the data needs and interests of the Commission, other agencies, and stakeholders, and the evolution of sampling methodologies specific to large river ecosystems.
Study Design
Previous studies of the large rivers of the basin included:
- Basinwide documentation of water quality and biological conditions (2002, 2005, 2007–2011, 2013);
- Data collection in geographically underrepresented areas (2016–2019); and
- Assessment of the river/impoundment system in the lower 70 miles of the mainstem Susquehanna River (2012, 2014, 2020–2022).
In 2023, the Commission adopted a spatially balanced probability design to select Large River Survey sites. The Commission’s large river classification includes Medium Mainstem Rivers (1,000 to 5,000 square mile drainage area) and Large Rivers (greater than 5,000 square miles). Each year, new sites are randomly chosen using a Generalized Random Tessellation Stratified (GRTS) design (spsurvey R package; Dumelle and others, 2023; Olsen and others, 2012). GRTS designs produce a representative sample of sites reflecting the spatial distribution of the medium and large rivers in the basin. The resulting dataset developed from these randomly chosen sites will allow the Commission to make inferences about basinwide conditions in large river ecosystems, and can also be used by state regulatory agencies in Clean Water Act 305(b) reporting.
Types of Data Collected
Muskellunge captured in the Susquehanna River near Owego, NY
Biological Communities
Fish and other aquatic organisms can be viewed as living indicators of stream health and the long-term effects of ecosystem stress. The Commission conducts fish surveys in large rivers using boat electrofishing techniques adapted from the U.S. Environmental Protection Agency (USEPA). The Pennsylvania Department of Environmental Protection’s (PADEP’s) semi-wadeable protocols are used for sampling benthic macroinvertebrates.
Collecting water samples for lab submission
Habitat
Physical habitat conditions within a river influence the composition of the biological community. Factors such as substrate type, instream cover, and riparian vegetation determine whether or not a stream reach is suitable for particular fish species or macroinvertebrates. The physical habitat at large river sites is assessed using a modified version of the USEPA’s Rapid Bioassessment Protocol (RBP) (Barbour and others, 1999). Assessment criteria for riffle/run or glide/pool habitats were used depending on the dominant habitat type within the sampling reach.
Macroinvertebrate sampling
Water Quality
Water quality monitoring data are used by state and federal regulatory agencies to identify current and emerging problems with contaminants, and to determine compliance with drinking water, recreational use, and aquatic life standards. The Commission measures temperature, dissolved oxygen, pH, specific conductivity, and turbidity in the field using handheld meters. Water samples are also sent to an accredited lab to be analyzed for the following parameters: alkalinity, metals (aluminum, calcium, iron, magnesium, manganese, potassium, sodium), nutrients (nitrate, phosphorus, total organic carbon), total suspended solids, and suspended sediment.
Site Ratings
Susquehanna River at Nichols, NY
Each Large River Survey site receives condition category ratings of excellent, good, fair, poor, or very poor for macroinvertebrates, habitat, and water quality based on numeric Semi-Wadeable Multimetric Index (SWMMI; Shull, 2018), Rapid Bioassessment Protocol (RBP, 1999), and Water Quality Index (WQI; Berry and others, 2020) scores. Table 1 summarizes the scoring ranges and corresponding condition categories for each index.
PADEP’s SWMMI was used to assess the macroinvertebrate community. This index was developed for use in large (>1,600 mi2), free-flowing river systems and includes two sets of metrics specific to Summer (August-September) and Fall (November-December) collection timeframes. Scores from the individual metrics are incorporated into a single index score with values ranging from 0 to 100.
Physical habitat is categorized based on 11 physical stream characteristics pertaining to substrate, pool and riffle composition, shape of the channel, conditions of the banks, and the riparian zone on a scale of 0-20 (20 being optimal). These 11 scores are added together to produce a total RBP habitat score ranging from 0 to 220.
The Commission’s Susquehanna River Basin WQI is used to evaluate water quality conditions. The WQI produces three separate category scores for metals, nutrient enrichment, and development, which are then averaged to produce an overall water quality score between 0 and 100.
Table 1. Summer/Fall Semi-Wadeable Multimetric Index (SWMMI), Rapid Bioassessment Protocol (RBP), and Water Quality Index (WQI) Scoring Ranges for Condition Category Ratings
| Condition Category | Summer SWMMI | Fall SWMMI | RBP Score | WQI Score |
|---|---|---|---|---|
| Excellent | ≥86 | ≥90 | ≥176 | ≥85 |
| Good | 70 - 85 | 75 - 89 | 121 - 175 | 62.01 - 84.99 |
| Fair | 49 - 69 | 57 - 74 | 66 - 120 | 42.93 - 62 |
| Poor | 34 - 48 | 35 - 56 | ≤ 65 | 30.99 - 42.92 |
| Very Poor | ≤ 33 | ≤ 34 | -- | ≤ 30.98 |
The Commission’s Susquehanna River Basin Water Quality Index (WQI) is used to evaluate water quality conditions. The WQI produces three separate category scores for metals, nutrient enrichment, and development, which are then averaged to produce an overall water quality score between 0 and 100.
Probabilistic Stream & River Survey Dashboard
Probabilistic Stream & River 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. EPA 841-B-99-002. U.S. Environmental Protection Agency, Office of Water, Washington, D.C.
Berry, J.L., L.Y. Steffy, and M.K. Shank. 2020. Development of a Water Quality Index (WQI) for the Susquehanna River Basin. Susquehanna River Basin Commission (Pub. No. 322), Harrisburg, Pennsylvania. www.srbc.gov/our-work/reports-library/technical-reports/322-water-quality-index-2020/.
Dumelle, M., T. Kincaid, A.R. Olsen, and M. Weber. 2023. spsurvey: Spatial Sampling Design and Analysis in R. Journal of Statistical Software 105(3):1-29. (doi:10.18637/jss.v105.i03)
Hoffman, J.L.R. 2003. Susquehanna River Pilot Study: Large River Assessment Project. Publication 228. Susquehanna River Basin Commission, Harrisburg, Pennsylvania.
Olsen, A.R., T.M. Kincaid, and Q. Payton. 2012. Spatially balanced survey designs for natural resources. Design and Analysis of Long-Term Ecological Monitoring Studies. R.A. Gitzen, J.J. Millspaugh, A.B. Cooper, and D.S. Licht. Cambridge, UK, Cambridge University Press: 126-150.
Shull, D. 2018. Semi-Wadeable Large River Macroinvertebrate Assessment Method. Chapter 2.4 in Water Quality Assessment Methodology for Surface Waters, D. Shull and R. Whiteash, 2023, PADEP Office of Water Programs, Bureau of Clean Water. Harrisburg, Pennsylvania.