Health of Freshwater Streams in the Chesapeake Bay Watershed

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Chesapeake Bay Program Indicator Framework

Reporting Level Indicators

Indicator and Data Survey

A.  Category/Name/Source/Contact

(1) Category of Indicator

___ Factors Impacting Bay and Watershed Health

___ Restoration and Protection Efforts

_X__ Watershed Health

___ Bay Health

(2) Name of Indicator:

Health of Freshwater Streams in the Chesapeake Bay Watershed

(3) Data Set Description:  

For what purpose(s) were the data collected? (e.g., tracking, research, or long-term monitoring.) All of the above

Which parameters were measured directly? Habitat, water quality, and benthic biometrics were measured directly. See list below:

Habitat metrics: Anthropogenic Alternations, Bank Stability, Channel Alteration, Habitat Heterogeneity, Instream Condition, Riparian Zone condition, Substrate Quality 

Water quality metrics:

pH , Conductivity 


# EPT taxa, % Dominant taxon, Hilsenhoff Family Biotic Index, % EPT, % Clingers, Taxa Richness, % Collectors, # Ephemeroptera, % Intolerant Urban, % Ephemeroptera, # Scrapers, % Climbers

Which were obtained by calculation? The overall benthic index of biotic integrity is calculated using all of the above collected data.

(4) Source(s) of Data: Maryland Department of Natural Resources, Pennsylvania Department of Environmental Protection, Virginia Department of Environmental Quality, West Virginia Department of Environmental Protection, Delaware Department of Natural Resources and Environmental Control, Prince Georges County, Montgomery County, Fairfax County, VA, United States Forest Service, Susquehanna River Basin Commission, US Environmental Protection Agency, Maryland Stream Waders, Virginia Commonwealth University INSTAR program. 

Is the complete data set accessible, including metadata, data-dictionaries and embedded definitions?  If yes, please indicate where complete dataset can be obtained. Complete dataset can be obtained from CBPO

(5) Custodian of Source Data (and Indicator, if different): Katie Foreman, University of Maryland Center for Environmental Science, CBPO and Jackie Johnson, Interstate Commission on the Potomac River Basin, CBPO

(6) CBPO Contact: Katie Foreman, 1-800-YOUR-BAY ext. 837

B.  Communication Questions

(complete either part 1, 2, or 3)

1.  Restoration and Protection Efforts indicators only

(7a) How much has been completed since 1985 (or baseline year)?  How much has been completed since 2000?

(8a) How much was done last year?

(9a) What is the current status in relation to a goal?

(10a) What is the key story told by this indicator?

(11a) Why is it important to report this information?

(12a) What detail and/or diagnostic indicators are related to this reporting level indicator? (Detail and diagnostic indicators can be spatially-specific, parameter-specific, temporally-specific information, etc.)

2.  Bay Health or Watershed Health indicators only

(7b) What is the long-term trend?  (since start of data collection) 

Since this indicator is relatively new, it has not been in use long enough to characterize a long-term trend, so only the average B-IBI scores from 2000-2008 data are portrayed.   Trends are difficult to determine because many programs monitor benthic macroinvertebrates on a rotating cycle, with data from one year representing a two- to 10-year period.  There are some sites that have been sampled several times, and the potential for identifying trends at these sites will be explored in the coming year.

(8b) What is the short-term trend? (10-year trend) Since this indicator is relatively new, it has not been in use long enough to characterize a short-term trend, so only the average B-IBI scores from 2000-2008 data are portrayed. 

 (9b) What is the current status in relation to a goal? Healthy fresh water streams are intrinsically related to a healthy Bay.  Although there is no quantified goal for categorization of sampling sites to meet an overall watershed health goal, it can generally be said that a healthy Bay Watershed would have the majority of the sites ranked as fair, good, or excellent. Although this indicator cannot be related to a quantifiable goal at this time, researchers are working on developing a way to relate this information to a watershed health goal in the future. 

(10b) What is the key story told by this indicator? The health of streams varies from very poor to excellent throughout the Bay Watershed (see results on the map).  Although sampling densities differ across the watershed, some generalizations about the health of streams can be made.  For instance, streams tend to be in very poor to fair condition around large urban areas such as metropolitan Washington, DC (see map inset). Streams in heavily farmed or mined areas are also often in very poor to fair condition.  In contrast, streams tend to have good to excellent conditions in forested areas with ample natural habitat and low levels of pollution, such as in the southwestern Pennsylvania region of the watershed (see map inset).  Overall, the analysis showed that out of 10,452 sampling sites in the watershed, 4,903 of the sites had very poor or poor conditions and 3,464 sites had good or excellent conditions.  The results from this indicator will help managers and watershed groups focus efforts to restore streams needing improvement or protecting the quality of the healthiest streams. 

(11b) Why is it important to report this information?

Healthy freshwater streams and rivers have local and regional importance. Clean waterways are a benefit to residents who use them for drinking water, family activities, business and other purposes. The watershed’s streams, creeks and rivers also eventually flow into the Bay, so their water quality has a direct impact on the health of the estuary. 

An effective way to measure the health of freshwater streams and rivers is to study the many tiny creatures that live in these waters. The abundance and diversity of snails, mussels, insects and other bottom-dwelling organisms -– known as benthic macroinvertebrates -– are good indicators of the health of streams because these creatures can’t move very far and they respond in certain predictable ways to pollution and environmental stresses.

 (12b) What detail and/or diagnostic indicators are related to this reporting level indicator? Benthic macroinvertebrate health status map

3.  Factors Impacting Bay and Watershed Health indicators only

(7c) What is the long-term trend?  (since start of data collection)

(8c) What is the short-term trend? (5-year trend and 10-year trend)

(9c) What is the current status?

(10c) What is the key story told by this indicator?

(11c) Why is it important to report this information?

(12c) What detail and/or diagnostic indicators are related to this reporting level indicator?

C.  Temporal Considerations

(13) Data Collection Date(s): Many programs monitor benthic macroinvertebrates on a rotating cycle, with data from one year representing a two- to 10-year period.  Although only the 2008 reporting year is shown, many states monitor benthic macroinvertebrates on a rotating cycle with data included in one reporting year that can reflect a 2 - 10 year period.  

(14) Planned Update Frequency (e.g. - annual, bi-annual):

(a) Source Data: bi-annual

(b) Indicator: bi-annual

(15) For annual reporting, month spatial data is available for reporting: Data is available every 2 years through the 305(b)/303(d) reporting process.

D.  Spatial Considerations

(16) Type of Geography of Source Data (point, line polygon, other): point data

(17) Acceptable Level of Spatial Aggregation (e.g. - county, state, major basin, tributary basin, HUC): No level of aggregation available at this time due to differences sampling designs from the different data sources.

(18) Are there geographic areas with missing data?  If so, where? District of Colombia and New York

(19) The spatial extent of this indicator best described as:

(a) Chesapeake Bay (estuary)

(b) Chesapeake Bay Watershed

(c) Other (please describe): _______________________

Please submit any appropriate examples of how this information has been mapped or otherwise portrayed geographically in the past. Information on state’s 303(d) assessments were mapped in the 2007 Health and Restoration Assessment Report.  The current map is derived using different methodology from the 2007 map and has used the same methodology as the 2008 Stream Health Indicator Map.

(20) Can appropriate diagnostic indicators be represented geographically? Yes.  Please see benthic macroinvertebrate health status map.

E.  Data Analysis and Interpretation

(Please provide appropriate references and location of documentation if hard to find.)

(21) Is the conceptual model used to transform these measurements into an indicator widely accepted as a scientifically sound representation of the phenomenon it indicates?  (i.e., how well do the data represent the phenomenon?)  This is a new indicator that has undergone extensive technical and peer review by Chesapeake Bay Partnership members of the non-tidal water quality workgroup as well as the monitoring and analysis subcommittee. Data collection, data analysis and QA/QC are conducted by the principal investigators/scientists. The data are peer reviewed by scientists on the workgroup. Data selection and interpretation, the presentation of the indicator, along with all supporting information and conclusions, are arrived at via consensus by the scientists. Methodology used to create this indicator is published in a peer-reviewed scientific journal (Astin 2006, 2007).  The workgroup presented the indicator to the subcommittee where extensive peer review by Bay Program managers occurs.  

(22) What is the process by which the raw data is summarized for development and presentation of the indicator?  Benthic Macroinvertebrates are collected in the field and their communities are summarized by basic benthic biometrics.  The non-tidal workgroup has developed a Chesapeake Bay Basin-wide B-IBI to score each sampling event’s benthic community in a standardized fashion. (Foreman et al. 2008, Astin 2006, 2007).  Once sampling events were scored, B-IBI scores were averaged for each site over the dataset to create one score for each site.  These scores are then rated on a qualitative scale of very poor to excellent.

(23) Are any tools required to generate the indicator data (e.g. - Interpolator, watershed model) Yes.  The Chesapeake Bay Basin-wide B-IBI. (Foreman et al. 2008).

(24) Are the computations widely accepted as a scientifically sound? Yes.  This index uses multiple metrics to assess species richness and composition, as well as the number and abundance of indicator species.  The development of a Chesapeake B-IBI was based on methods that are published in a scientific peer-reviewed journal. (Astin 2006, 2007).  

(25) Have appropriate statistical methods been used to generalize or portray data beyond the time or spatial locations where measurements were made (e.g., statistical survey inference, no generalization is possible)?  NA

(26) Are there established reference points, thresholds or ranges of values for this indicator that unambiguously reflect the desired state of the environment? (health/stressors only)  Yes.  The Chesapeake Bay Program (CBP) has adopted the approach of presenting indicators as a “percent of restoration goal achieved.” A passing grade of “an index value greater than or equal to a value of 21 on a scale of 7 - 35” (or “3 on a scale of 1 – 5”) was selected. This goal is directly comparable to the estuarine phytoplankton and benthic IBI restoration goals of “index values greater than or equal to 3 on a scale of 1 – 5.” This threshold relates to the qualitative scores of good and excellent and the upper portions of the category “fair” in the Chesapeake Bay B-IBI.

F.  Data Quality

(Please provide appropriate references and location of documentation if hard to find.)

(27) Were the data collected according to an EPA-approved Quality Assurance Plan?  

If no, complete questions 28a – 28d:

(28a) Are the sampling design, monitoring plan and/or tracking system used to collect the data over time and space based on sound scientific principles? Yes.

(28b) What documentation clearly and completely describes the underlying sampling and analytical procedures used?  

Please see:  

(USEPA 1997)


(28c) Are the sampling and analytical procedures widely accepted as scientifically and technically valid? Yes.  Most sampling procedures are modifications of the Environmental Protection Agency’s Rapid Bioassessment Protocols for Use in Stream and Wadeable Rivers (Plafkin et al. 1989).

Please see:

(28d) To what extent are the procedures for quality assurance and quality control of the data documented and accessible? Each organization has documented procedures for quality assurance within their sampling design documents (28b) and in the following links:

(29) Are the descriptions of the study or survey design clear, complete and sufficient to enable the study or survey to be reproduced?  Yes, please see 28b.

(30) Were the sampling and analysis methods performed consistently throughout the data record? No.  There are differences in sampling analysis and methodology between sampling agencies, please see 28b for references.  Please see table 1 and 2 with individual sampling organization’s methodology details at the end of this document. 

(31) If datasets from two or more agencies are merged, are their sampling designs and methods comparable? Sampling designs are not 100% comparable, however the development of the Chesapeake Bay Basin-wide B-IBI standardizes the data so it can be compared across jurisdictions (Astin 2006, 2007).

(32) Are uncertainty measurements or estimates available for the indicator and/or the underlying data set?  Yes, each data source has uncertainty measurements in data collection and a jackknife validation of the B-IBI estimates error associated with the B-IBI calculations (Foreman et al. 2008). 

(33) Do the uncertainty and variability impact the conclusions that can be inferred from the data and the utility of the indicator? Maybe, most issues of uncertainty and variability have been resolved in the indicator development.  However, more analysis needs to be done on how to continue to decrease the error that differences in sampling design and gear might have on final results. 

(34) Are there noteworthy limitations or gaps in the data record?  Please explain. New York and District of Colombia data are missing.  Efforts in the next year’s indicator will be made to incorporate that missing data. 

G.  Additional Information


(35) Please provide any other information about this indicator you believe is necessary to aid communication and any prevent potential miss-representation.

1.This dataset is missing data from New York and District of Colombia.  It should be noted that overall scoring of the health of benthic macroinvertebrates in the entire Chesapeake Bay Watershed is not complete. Every effort will be made to incorporate this data as well as others that become available in the future.

2.Although the reviewers of this indicator did not see any fatal flaws in the methodology, there is the intent to continue to improve upon the certainty of this indicator in accurately identifying benthic macroinvertebrate health.  Rigorous testing of biometrics used, classification schemes, scaling, and tolerance value discrepancies will be researched in the future to improve the accuracy of the indicator.  Future work will also include the development of methodologies to combine B-IBI results from different sampling designs (targeted vs. random) in order to provide and overall index value for the entire Chesapeake Bay Watershed.

3.This indicator used the same methodology as last year for scoring the B-IBI (Foreman et al. 2008), however major differences in this year’s assessment were that: a). there is almost three times as much data included from last year’s data sources as well as from new sources such as Maryland Stream Waders, US Environmental Protection Agency Wadeable Streams Assessment, and Virginia Commonwealth University INSTAR program. b). Updated criteria was used for the coastal plain ecoregion, these thresholds are merely the updated version of what was used last year.  These thresholds are the same that are used for Maryland Biological Stream Survey’s coastal plain assessment (Table 3).


Astin, L.E. 2006. Data synthesis and bioindicator development for nontidal streams in the interstate Potomac River basin, USA. Ecological Indicators 6: 664-685.

Astin, L. E. 2007. Developing biological indicators from diverse data: The Potomac Basin-wide Index of Benthic Integrity (B-IBI). Ecological Indicators 7: 895-908.

Foreman, K., Buchanan, C., Nagel, A., 2008. Development of ecosystem health indexes for non-tidal wadeable streams and rivers in the Chesapeake Bay basin.  Report to the Cheaspeake Bay Program Non-Tidal Water Quality Workgroup. December 5, 2008.

Karr, J.R. 1981. Assessment of biotic integrity using fish communities. Fisheries 6:21-27.

Plafkin, J. L. et al.  1989.  Rapid bioassessment protocols for use in streams and rivers:

Benthic macroinvertebrates and fish.  EPA/440/4-98/001.  U.S. Environmental

Protection Agency, Office of Water Regulations and Standards, Washington, D. C.

US Environmental Protection Agency. 1997. Field and laboratory methods for macroinvertebrate and habitat assessment of low gradient nontidal streams. Mid-Atlantic Coastal Streams Workgroup, Environmental Services Division, Region 3, Wheeling, WV; 23 pages with appendices.

Table 1.Benthic Macroinvertebrate sampling details for each data source in the Chesapeake Bay B-IBI



Table 2.  Links to information on methods for 2009 new data sources 

New Data source Weblink to methods
Maryland Stream Waders
Virginia Commonwealth University INSTAR program
EPA Wadeable Streams Assessment

Table 3: Updated thresholds for the coast plain ecoregion 

Benthic IBIs (metrics) Thresholds
Coastal Plain      
Number of Taxa  >=22 14-21 <14
Number of EPT  >=5  2-4  <2 
Number of Ephemeropetra  >=2 1-1  <1 
% Intolerant Urban >=28 10-27  <10
% Ephemeropetra >=11  0.8-10.9  <0.8 
Number of Scrapers  >=2 1-1  <1
% Climbers >=8 0.9-7.9 <0.9


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