Related Indicators: Nitrogen in Rivers Entering Chesapeake Bay

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Metadata

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: Chesapeake Bay watershed nitrogen flow-adjusted concentration trend indicators

(3) Data Set Description: 

 For what purpose(s) were the data collected? (e.g., tracking, research, or long-term monitoring.) -  Long-term monitoring.
 Which parameters were measured directly? Discharge and nitrogen concentrations at 34 long-term monitoring stream sites in the Chesapeake Bay watershed. 
 Which were obtained by calculation? Flow-adjusted concentration trends were calculated using ESTIMATOR, a 7-parameter water quality model (Langland et al. 2006).  Computations include both linear and non-linear time and flow coefficients.  Trends are presented as a “continuous” change over time for all sites. The model for trend estimation is calibrated for a single time period (period of record) rather than for a series of time intervals (such as the moving-window approached used in other analyzes for load estimation).

(4) Source(s) of Data: USGS, Maryland Department of Natural Resources, Delaware Department of Natural Resources and Environmental Control, Susquehanna River Basin Commission, New York Department of Environmental Conservation, Pennsylvania Department of Environmental Protection, Virginia Department of Environmental Quality, West Virginia Department of Environmental Protection, West Virginia Department of Agriculture.

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

(5) Custodian of Source Data (and Indicator, if different): Mike Langland, USGS and Mike Mallonee, Interstate Commission on the Potomac River Basin, CBPO

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

B.  Communication Questions

(complete either part 1, 2, or 3)
3.  Factors Impacting Bay and Watershed Health indicators only
(7c) 
What is the long-term trend? 

Over the past 23 years, nitrogen concentration trends are downward at the majority of long-term monitoring sites within the Bay watershed. The trend results indicate that in many locations, management actions, such as improved wastewater treatment and nonpoint-source pollution controls (i.e. urban stormwater runoff and agricultural runoff controls), have reduced nitrogen concentrations in streams.
• The majority of the flow-adjusted trends were downward, with 25 sites showing decreasing trends, 2 sites showing increasing trends, and 7 sites showing trends that were not statistically significant. 
• Data from the River Input Monitoring Program, which monitors nine tributaries immediately above tidal waters, shows downward trends in nitrogen at the Susquehanna, Potomac and James Rivers, the three largest tributaries to Chesapeake Bay. In addition, downward trends are shown for the Patuxent River in Maryland. Trend results for nitrogen were not significant at the Rappahannock, Mattaponi and Appomattox Rivers in Virginia. 
• Increasing trends are observed at the Pamunkey River in Virginia and the Choptank River which drains portions of Maryland and Delaware.
 (9c) What is the current status?
• Changes in nitrogen concentrations have been determined for the period 1985-2008 at 34 stream sites in the Chesapeake Bay watershed.  Of these, the majority of the flow-adjusted trends were downward, with 25 sites showing decreasing trends, 2 sites showing increasing trends, and 7 sites showing trends that were not statistically significant. 
• Downward trends in flow-adjusted concentrations indicate improvements in water-quality conditions, while upward trends may be used to identify watersheds that may require an increased level of pollution control. 
 (10c) What does this indicator tell us?
• Over the past 23 years, nitrogen concentration trends are downward at the majority of long-term monitoring sites within the Bay watershed. The trend results indicate that in many locations, management actions, such as improved wastewater treatment and nonpoint-source pollution controls (i.e. urban stormwater runoff and agricultural runoff controls), have reduced nitrogen concentrations in streams.
 (11c) Why is it important to report this information?
• Nitrogen is a nutrient that promotes plant and algal growth in aquatic ecosystems. Excess nitrogen from point and nonpoint sources may lead to eutrophication of streams, impoundments, and bays and impairment of aquatic ecosystems.
• Nitrogen concentrations are highly variable and strongly related to streamflow conditions. Flow-adjusted trends are calculated in order to statistically determine whether concentrations have changed over time and removing the effects of natural variations in streamflow. Because flow-adjusted trends are independent of streamflow variations, they permit evaluation of the changes in stream quality that may result from nutrient-reduction actions or other changes within the watershed.
• Nitrogen concentrations are monitored near the head of tide (River Input Monitoring Program) in nine of the Bay's major tributaries, and at 25 locations upstream from the River Input sites. 
 (12c) What detail and/or diagnostic indicators are related to this reporting level indicator?

Other indicators measuring nutrient and sediment pollution in the Bay Watershed are related to this indicator – for instance the reporting level indicators of Total Nitrogen Loads Delivered to the Bay.

C.  Temporal Considerations

(13) Data Collection Date(s): Water year (October 1-September 30) 1985-2008, starting dates ranged from 1985 to 1990 through 2008.


(14) Planned Update Frequency (e.g. - annual, bi-annual):
 (a) Source Data:
a. Annual
 (b) Indicator: Annual

(15) For annual reporting, month spatial data is available for reporting: Data are typically analyzed by the USGS by April of each year; therefore there is a one year lag in the availability of data for reporting to the Bay Barometer.

D.  Spatial Considerations

(16) Type of Geography of Source Data (point, line polygon, other): Symbols are mapped at sampling locations indicating the direction and magnitude (in % change) of change in nutrient and sediment concentrations.  Arrows with different directions and sizes are portrayed to present this information; no significant change is signified by a black dot.

(17) Acceptable Level of Spatial Aggregation (e.g. - county, state, major basin, tributary basin, HUC):

Entire watershed

 (18) Are there geographic areas with missing data?  If so, where?
Most of the monitoring is conducted upstream from the head of tide. Thus, the trends are not reflected for the majority of the Coastal Plain areas of the watershed.

(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.

The flow-adjusted trends indicator is calculated, and results and maps are published annually by the U.S. Geological Survey as part of a larger effort to determine loads and trends in nutrient and sediment concentrations and streamflow in the Chesapeake Bay watershed.

(20) Can appropriate diagnostic indicators be represented geographically?

Yes.

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?) 

Yes.  The flow-adjusted trends indicator is calculated, and published annually by the U.S. Geological Survey as part of a larger effort to determine loads and trends in nutrient and sediment concentrations and streamflow in the Chesapeake Bay watershed. A complete description of data analysis methods can be found in Langland, M. J., and others, Changes in streamflow and water quality in selected nontidal basins in the Chesapeake Bay watershed, 1985-2004: U.S. Geological Survey Scientific Investigations Report 2006-5178, 75 p., available online athttp://pubs.usgs.gov/sir/2006/5178/

(22) What is the process by which the raw data is summarized for development and presentation of the indicator?  

Refer to Langland, M. J., and others, Changes in streamflow and water quality in selected nontidal basins in the Chesapeake Bay watershed, 1985-2004: U.S. Geological Survey Scientific Investigations Report 2006-5178, 75 p., available online athttp://pubs.usgs.gov/sir/2006/5178/
 
(23) Are any tools required to generate the indicator data (e.g. - Interpolator, watershed model)

USGS ESTIMATOR model

(24) Are the computations widely accepted as a scientifically sound?  Yes.  Models used and calculations performed are published in peer-reviewed publications (Cohn et. al 1989 and Langland et al. 2006).

(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)?

Every effort was made to minimize extrapolations beyond the available data and technology of the water quality models.
 
(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)

• Stream quality is associated with lower nutrient concentrations; therefore, the goal for the flow-adjusted trend indicator is to observe downward trends in flow-adjusted nitrogen concentrations at most monitoring sites in the watershed, and few upward trends. 
• The flow-adjusted trend indicator is used to describe the direction of change over the past 23 years. The amount of change in flow-adjusted trend required to meet load-reduction goals varies among tributaries.

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:

Yes

(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? 

The sampling and analytical methods adhere to the Chesapeake Bay Program’s guidance for the Nontidal Network, which may be found on the web at:   http://archive.chesapeakebay.net/pubs/subcommittee/msc/amqawg/Chapter%205%20Nov%2008%20Final.pdf
 
(28c) Are the sampling and analytical procedures widely accepted as scientifically and technically valid?

Yes. 

(28d) To what extent are the procedures for quality assurance and quality control of the data documented and accessible?

State and federal partners collecting data for this indicator have individual Quality Assurance Project Plans which document in detail each agency’s sampling and laboratory protocols.  Individual Quality Assurance Project Plans for this indicator are on file at the Chesapeake Bay Program Office:

1. Pennsylvania Department of Environmental Protection:
• Pennsylvania Quality Assurance Work Plan – Fixed Station Surface Water Quality Network Monitoring (Nov. 2007).

2. Susquehanna River Basin Commission (includes NY stations):
• Assessment of Nutrient Sources from Mainstem and Selected Watersheds in the Susquehanna River Basin – Quality Assurance/Quality Control Plan (Sept. 2009).

3. Maryland Department of Natural Resources:
• Non-tidal Network Program Nutrient and Sediment Load Trend Monitoring Quality Assurance Project Plan (July, 2009).

4. U.S. Geological Survey – Maryland, Delaware and D.C. Water Science Center:
• Maryland River Input Nutrient and Sediment Loading Trends Component Quality-Assurance Project Plan (July 2009).

5. U.S. Geological Survey – West Virginia Water Science Center:
• WV DEP Potomac River Nontidal Nutrient and Sediment Sampling – Quality Assurance Project Plan (April 2005).

6. U.S. Geological Survey – Virginia Water Science Center:
• Quality Assurance Project Plan for the Virginia River Input Monitoring Program (July 2008).

7. Virginia Department of Environmental Quality
• Virginia CBP Non-Tidal Network Monitoring Program Quality Assurance/Quality Control Project Plan (July 2009). 

(29) Are the descriptions of the study or survey design clear, complete and sufficient to enable the study or survey to be reproduced? 

Yes, see 28b

(30) Were the sampling and analysis methods performed consistently throughout the data record?

Yes, see 28b

(31) If datasets from two or more agencies are merged, are their sampling designs and methods comparable?

Yes

(32) Are uncertainty measurements or estimates available for the indicator and/or the underlying data set?

Yes, the flow-adjusted trend analysis has an associated confidence interval

(33) Do the uncertainty and variability impact the conclusions that can be inferred from the data and the utility of the indicator?

No

(34) Are there noteworthy limitations or gaps in the data record?  Please explain.
There are no major limitations in the data record, data was collected in a consistent manner from 1985-2008.  However, most of the monitoring is conducted upstream from the head of tide. Thus, the trends are not reflected for the majority of the Coastal Plain areas of the watershed.

G.  Additional Information

(optional)

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


• The flow-adjusted trends indicator is calculated, and published annually by the U.S. Geological Survey as part of a larger effort to determine loads and trends in nutrient and sediment concentrations and streamflow in the Chesapeake Bay watershed. A complete description of data analysis methods can be found in Langland, M. J., and others, Changes in streamflow and water quality in selected nontidal basins in the Chesapeake Bay watershed, 1985-2004: U.S. Geological Survey Scientific Investigations Report 2006-5178, 75 p., available online athttp://pubs.usgs.gov/sir/2006/5178/
• The US Environmental Protection Agency Chesapeake Bay Program (CBP), in partnership with USGS, and agencies in six states throughout the Chesapeake Bay watershed, monitors streamflow, nutrients, and sediment as part of the CBP Nontidal Water-Quality Monitoring Network (link to the map of the network). There are 85 sites in the network, however only 34 of these sites have adequate long-term record to calculate flow-adjusted concentration trends.  
• The network includes the River Input Monitoring Program which monitors streamflow and water quality at nine sites upstream from the head of tide at each of the major river basins draining to the Bay. The River Input sites collectively represent 78 percent of area of the watershed and range in size from the Susquehanna River (27,000 square miles) to the Choptank River (100 square miles).  These nine rivers account for approximately 93 percent of the streamflow entering Chesapeake Bay from the nontidal part of its watershed.  However, many of the largest populated cities within the watershed are located downstream of these monitoring sites in the Coastal Plain region of the watershed.
• Results from the CBP Nontidal Water-Quality Monitoring Network are being used by resource managers, policy makers, and concerned citizens to help evaluate the effectiveness of strategies aimed at reducing nutrients and sediment entering streams and rivers in the Chesapeake Bay watershed and, eventually, the tidal waters of the Bay. 
• Most of the monitoring is conducted upstream from the head of tide. Thus, the trends do not reflect the effects of management actions that are implemented in the majority of the Coastal Plain areas of the watershed. 
• There are multiple factors affecting nutrient trends. The major factors include changes in nutrient sources and land use, population increase, implementation of management actions, and the influence of watershed characteristics including the lag time between implementing management actions to decrease nutrient pollution and detecting a water-quality improvement.

References

Cohn, T.A., DeLong, L.L., Gilroy, E.J., Hirsch, R.M., and Wells, R.M., 1989, Estimating constituent loads: Water Resources Research, v. 25, no. 5, p. 937-942.
Langland, M.J., Raffensperger, J.P., Moyer, D.L., Landwehr, J.M., and Schwarz, G.E., 2006, Changes in Streamflow and Water Quality in Selected Nontidal Basins in the Chesapeake Bay Watershed, 1985-2004: U.S. Geological Survey Scientific Investigations Report 2006-5178, 75 p. 
Linker, L. C., G. W. Shenk, R. L. Dennis, and J. S. Sweeney. 2000. Cross-media models of the Chesapeake Bay watershed and airshed. Water Quality and Ecosystem Modeling 1: 91-122.
Moyer, D. L. 2005. Quality Assurance Project Plan for the Virginia River Input Monitoring Program. USGS Water Resources.
Runkel, R. L., C. G. Crawford, and T. A. Cohn. 2004. Load Estimator (LOADEST): A FORTRAN Program for Estimating Constituent Loads in Streams and Rivers, p. 69. U.S. Geological Survey Techniques and Methods Book 4, Chapter A5. USGS.
Tenbus, F. J. 2006. Quality Assurance Project Plan for the Maryland River Input Monitoring Program, river input nutrient and sediment loading trends component, p. 41. USGS Water Resources.
U.S. Environmental Protection Agency. 2003. Setting and allocating the Chesapeake Bay basin nutrient and sediment loads. US EPA Chesapeake Bay Program Office.

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