Bay Watershed Population

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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

_x_ Factors Impacting Bay and Watershed Health

___ Restoration and Protection Efforts

___ Watershed Health

___ Bay Health

(2) Name of Indicator: Bay Watershed Population

(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? N/A. 

Which were obtained by calculation? 

oPopulation:  The 1900-2000 data is based on decadal US Census Bureau data apportioned to the Bay watershed by the CBPO.  The 2001 - 2008 data is based on the annual population estimates produced by the US Census Bureau apportioned to the Bay watershed by the CBPO.  The 2010 - 2030 data is based on County population projections produced by each state and the Washington Council of Governments and apportioned to the Bay watershed by the CBPO.

(4) Source(s) of Data: CBPO Data Center, Peter Claggett (800-YOUR-BAY ext 771)

Is the complete data set accessible, including metadata, data-dictionaries and embedded definitions? If yes, please indicate where complete dataset can be obtained.  http://archive.chesapeakebay.net/sta...lation2008.xls

(5) Custodian of Source Data (and Indicator, if different): CBPO Data Center, Peter Claggett (800-YOUR-BAY ext 771)

(6) CBPO Contact: Peter Claggett (800-YOUR-BAY ext 771)

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?  (since start of data collection) 

From 1950 through 2008, the Bay watershed population increased from 8,385,982 to 16,883,751.

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

The 10-year trend is not available, since the most recent annual data points are 2000 through 2008. During this time, population increased from 15,700,408 to 16,883,751.

(9c) What is the current status?

16,883,751 people live in the watershed.

 (10c) What does this indicator tell us?

•While the overall population of the Bay watershed continues to grow, population changes vary from state to state and region to region. Some areas are gaining population at a high rate, while populations in other areas are leveling out or declining.

•Experts predict that population will increase to more than 20 million by 2030.

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

•The way humans use the land has the greatest impact on the Bay and local waterways. Natural areas like forests and wetlands have a positive effect on water quality, while areas developed for farming or cities generally have a negative impact.

•The decline of the Chesapeake Bay is directly linked to the rise in population in the watershed: since 1950, the number of residents has more than doubled. Projections through 2030 show continued population growth, loss of natural areas and increases in urban development, which are all challenges to protecting and restoring the Chesapeake. 

•Even more influential than population growth is the corresponding development. People are moving into sprawling suburbs and living in bigger houses on larger lots, causing forests, farms and other valuable lands to be transformed into subdivisions, shopping centers and parking lots. This land conversion severely impacts the health of streams, rivers and the Bay.

•Impervious surfaces such as roads and rooftops do not allow water to filter into the ground. Instead rainfall runs off, picking up pollution and quickly carrying it into waterways. 

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

N/A

C.  Temporal Considerations

(13) Data Collection Date(s): 

Population: Decennial census from 1950-2000, annual estimates from 2001 to 2008, and decadal projection from 2010-2030. Impervious Surface: 1990 and 2000.

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

(a) Source Data: Population: every year 

b) Indicator: Population: every year 

(15) For annual reporting, month spatial data is available for reporting: N/A

D.  Spatial Considerations

(16) Type of Geography of Source Data (point, line polygon, other): The population data is a county spreadsheet linked to county TIGER polygon files.

(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?

N/A

(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.

(20) Can appropriate diagnostic indicators be represented geographically?

N/A

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?)  

There are many acceptable ways to apportion county population to watershed boundaries.  We used a population and residential road weighted allocation method outlined in Claggett, P. and C. Bisland, 2004, Assessing the vulnerability of forest and farmlands to development in the Chesapeake Bay watershed, in Proceedings of the IASTED International Conference on Environmental Modeling and Simulation, November 22-24, 2004, St. Thomas, U.S. Virgin Islands.

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

For the population data, see Claggett, P. and C. Bisland, 2004, Assessing the vulnerability of forest and farmlands to development in the Chesapeake Bay watershed, in Proceedings of the IASTED International Conference on Environmental Modeling and Simulation, November 22-24, 2004, St. Thomas, U.S. Virgin Islands.

For the impervious data, a standard GIS zonal summary function was used to assess the extent of impervious surface in the watershed.

(23) Are any tools required to generate the indicator data (e.g. - Interpolator, watershed model)

Geographic Information System software and spreadsheet software.

(24) Are the computations widely accepted as a scientifically sound? 

The population methods have been published in the proceedings of a scientific conference and the impervious surface mapping methods have been published in a peer-reviewed scientific journal.

(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)? 

N/A

(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) 

N/A

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:

No

(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?  

Claggett, P. and C. Bisland, 2004, Assessing the vulnerability of forest and farmlands to development in the Chesapeake Bay watershed, in Proceedings of the IASTED International Conference on Environmental Modeling and Simulation, November 22-24, 2004, St. Thomas, U.S. Virgin Islands.

Goetz, S.J., Jantz, C.A., Prince, S.D., Smith, A.J., Varlyguin, D. and Wright, R. , 2004, Integrated analysis of ecosystem interactions with land use change: the Chesapeake Bay watershed, Pages 263-275 in R.S. DeFries, G.P. Asner and R.A. Houghton (Editors), Ecosystems and Land Use Change. American Geophysical Union, Geophysical Monograph Series, Washington DC.

(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?

See above references.

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

Yes.

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

Yes.

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

Only the population projections were derived by different agencies using potentially different methods and slightly different assumptions.  It is not yet known the degree to which the methods used by each state are comparable. 

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

No.

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

Yes.

(34) Are there noteworthy limitations or gaps in the data record?  Please explain.

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.

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