Data loggers were exchanged bi-weekly. Loggers were deployed simultaneously at two depths at stations XHH4931 and XHH4916.
When data loggers were exchanged, water samples for pigments, nutrients and suspended solids were collected for later analysis. At the same time, Secchi disk depth was measured and a HydroLab (series III or IV) water quality sonde was used to collect discrete water temperature, salinity, dissolved oxygen and pH data. Light attenuation was also measured using a LiCor instrument.
Shallow water monitoring data describes the 2007 state of forty-nine shallow water sites on Chesapeake Bay tributaries using key water quality indicators.
The information is integrated with data from other Bay water quality stations and living resources monitoring projects and used to understand linkages, temporal variation and long-term trends.
Water quality data are used to refine, calibrate and validate Chesapeake Bay ecological models. The models are used to develop and assess water quality criteria with the goal of removing the Chesapeake Bay and its tidal rivers from the list of impaired waters.
Data users who desire very detailed information about Water Quality Monitoring data-definition, sampling-procedures and data-processing are encouraged to refer to the two documents listed below. The documents may be obtained from the Chesapeake Bay Program Office.
Water Quality Database - Database Design and Data Dictionary Prepared For: U.S. Environmental Protection Agency, Region III, Chesapeake Bay Program Office, January 2004. <http://www.chesapeakebay.net/pubs/cbwqdb2004_RB.PDF>
The most current version of the Water Quality Data Dictionary - Online may be found at: [<http://archive.chesapeakebay.net/data/data_dict.cfm?DB_CODE=CBP_WQDB> ].
Quality Assurance Project Plan for the Maryland Department of Natural Resources, Chesapeake Bay Shallow Water Quality Monitoring Program, for the period July 1, 2007 - June 30, 2008. [<http://mddnr.chesapeakebay.net/eyesonthebay/documents/swm_qapp_2007_draft.pdf>]
The project was made possible with funding provided by The State of Maryland, the United States Environmental Protection Agency Chesapeake Bay Program, the National Atmospheric and Oceanic Administration Chesapeake Bay Program Office, the National Atmospheric and Oceanic Administration National Estuarine Research Reserve System program, the Oyster Recovery Partnership, Harford County Maryland and Anne Arundel County Maryland.
The YSI 6600 V2 or 6600 EDS sondes were configured with the following probes: 6560(conductivity/temperature); 6561(flat glass pH) or 6579(tall pH); 6136(turbidity); 6562(rapid pulse dissolved oxygen) or 6150(ROX); 6025(fluorescence/chlorophyll). Sondes at 2 sites were also configured with 6132 (blue-green pe) probes.
Resolution, range and accuracy specifications for the sonde and probes may be obtained from the manufacturer. [https://www.ysi.com/ysi/Support]
Procedures used to control and assure the accuracy of field measurements consisted of calibration of field instruments, verification of calibrations, equipment maintenance, and collection of filter blanks. Details of how data acquired with YSI sondes were quality assured and quality controlled may be found in the process description elements in the Lineage portion of this metadata record.
Water quality laboratory analysis results were used to calibrate and cross-check sonde data for accuracy. Daily quality control checks (including the running of blanks and standards) were used to control and assure laboratory accuracy.
Accuracy of Chesapeake Biological Laboratory, Nutrient Analytical Services Laboratory (CBL NASL) and Maryland Department of Health and Mental Hygiene Environmental Chemistry Division (DHMH ECD) laboratory results was also assessed through DNR's participation in the Chesapeake Bay Coordinated Split Sample Program (CSSP), a split sampling program in which five laboratories involved in Chesapeake Bay monitoring analyze the coordinated split samples. CSSP was established in June 1989 to establish a measure of comparability between sampling and analytical operations for water quality monitoring throughout the Chesapeake Bay and its tributaries. DNR followed the protocols in the Chesapeake Bay Coordinated Split Sample Program Implementation Guidelines (EPA 1991) and its revisions. Split samples were collected quarterly. Results were analyzed by appropriate statistical methods to determine if results differed significantly among labs. If a difference occurred, discussions began regarding techniques and potential methods changes to resolve discrepancies.
Additionally, CBL NASL and DHMH ECD participated two times per year in the United States Geologic Survey (USGS) reference sample program.
During 2007, at all but two stations, water quality monitoring sondes were deployed at a single depth. At two stations: The Sill (XHH4916) and Possum Point (XHH4931), sondes were deployed at two depths: one meter from the surface and 0.3 meters from the bottom.
Values in the 'LAYER' column of sonde data files may be used to determine the depth at which a sonde was deployed. Sonde data from all 2007 sites, except XHH4916 and XHH4931, list a value of 'BS', 'below surface' in the LAYER column.
For stations XHH4916 and XHH493, a LAYER column value of 'B' indicates the sonde was deployed 0.3 meters above the bottom. A LAYER column value of 'S' indicates the sonde was deployed 1 meter below the surface.
No post-calibration data were used in data verification of sonde data collected at station XKH0375 (Susquehanna Flats) during the 6-Sep-07 through 20-Sep-07. Data verification was based on in situ match-ups only.
21-Aug-07 station XDB4544 (Blossom Point) was relocated to deeper water. The station was moved ~ 100m Northwest.
The 2007 Continuous Monitoring project dataset includes twelve months of sonde records from the continuous monitoring stations: WXT0013 (Iron Pot Landing), PXT0455 (Jug Bay) and XHH3851 (Sycamore Pt.). The sondes at stations: MTI0015 (Mataponi) and XJG7035 (Otter Point Creek) were deployed eleven months. Sonde data were collected for ten months at stations: XDM4486 (Bishopville Prong), NPC0012 (Newport Creek), XBM8828 (Public Landing) and TUV0021 (Turville Creek). Nine month deployments occurred at stations XIE5748 (Baltimore Harbor), XJH2362 (Betterton), XKH2949 (Havre de Grace), XJI8369 (Long Point), XHH4931 (Possum Point - Bottom), XHH4931 (Possum Point - Surface), XKH2870 (Stump Point), XHH4916 (The Sill) and XHH4916 (The Sill). Deployments at stations: XCD5599 (Breton Bay), XKH2797 (Carpenters Point), XEG2646 (Casson Pt.), XGG6667 (CBEC), XKI5022 (Charlestown), XFB0231 (Fenwick), XEG4991 (Gary’s Creek), CHO0417 (High Banks), XKI0256 (Hollywood Beach), XEH5622 (Horn Point Lab), XJG4337 (Lauderick Creek), LMN0028 (Little Monie Creek), XKI3890 (Locust Point Marina), XEA3687 (Mattawoman), XFG5054 (Mulberry Pt.), XDE4587 (Pin Oak), XFB2184 (Piscataway), XDC3807 (Popes Creek), XHF0561 (Sandy Pt. - East Beach), XCC8346 (Swan Pt.), WIW0144 (Upper Ferry), XCJ6023 (Whitehaven) and XCC9680 (Wicomico Beach) lasted eight months. Sondes were deployed seven months at stations: XDB4544 (Blossom Pt), XJI2396 (Budd’s Landing), ZDM0001 (Harness Cr. Downstream), XEI7405 (Jamaica Pt), XGG8359 (Kent Narrows Inside), XBE8396 (Piney Point), XDB8884 (Port Tobacco), XHF0460 (Sandy Pt. - South Beach) and XBF7904 (St Georges Creek). The sondes at stations: ZDM0002 (Harness Cr. Upstream) and XGG8458 (Kent Narrows Outside) were deployed six months and the sonde at stations: XKH0375 (Susquehanna Flats) was deployed five months. Finally, the sonde at station XJI1871 (Georgetown Yacht Basin) was deployed for two months.
The user may discover a few interruptions in sonde datasets. In most cases, these interruptions were related to short-term problems with sonde operation.
Concerns about possible equipment damage due to freezing conditions necessitated the temporary removal of sondes at five locations. There are no sonde data from station MTI0015 (Mataponi) from 18-Jan-07 to 6-Mar-07; station XJG7035 (Otter Point Creek) from 18-Jan-07 to 5-Mar-07; station WXT0013 (Iron Pot Landing) from 8-Feb-07 to 6-Mar-07; station PXT0455 (Jug Bay) from 8-Feb-07 to 6-Mar-07 and station XHH3851 (Sycamore Point) from 8-Feb-07 to 9-Mar-07.
No data were acquired at station XHH3851 (Sycamore Point) from 5-Jul-07 to 18-Jul-07 due to the failure of a communication cable connection. A power failure due to a flooded battery compartment resulted in a sonde data gap from 29-Jul-07 and 9-Aug-07 at station XCD5599 (Breton Bay). Another gap in sonde data, from 31-Jul-07 to 31-Aug-07 at station XHF0561 (Sandy Point East Beach), was caused by equipment damage sustained during a lightning strike.
The need to remove sonde tubes for re-conditioning, because of heavy fouling, resulted in data gaps at four sites. No sonde data were collected at: station XHH4916 (The Sill Bottom) from 20-Jun-07 to 18-Jul-07; station XHH4931 (Possum Point - Bottom) from 20-Jun-07 to 18-Jul-07; station XGG6667 (CBEC) from 21-Jun-07 to 19-Jul-07 and station XHH4931 (Possum Point - Surface) from 29-Aug-07 to 12-Sep-07.
On a few occasions, due to extreme low tide conditions, sondes were not submerged. These data are not included in the published dataset.
All other missing sonde attribute values were removed because the data were determined to be unreliable during the quality control process.
The Yellow Springs Instrument (YSI) 6600 data sondes were maintained and calibrated before and after each deployment in accordance with YSI recommendations. https://www.ysi.com/ysi/Support
FIELD MEASUREMENTS AND SAMPLING
SONDES:
The continuous monitoring sensors at the sites recorded seven water quality parameters every 15 minutes. Data were uploaded to DNR's web site <http://www.eyesonthebay.net> shortly after retrieval.
At all sites the seven water quality parameters measured continuously were: water temperature, specific conductance, salinity, dissolved oxygen, turbidity (NTU), fluorescence (used to estimate chlorophyll a) and pH. Sondes deployed at fixed depths also measured water depth.
Each monitoring station was equipped with a YSI 6600 sonde. The sonde logged data onto an internal memory, where it was stored until retrieval. Twelve stations were equipped with cellular telemetry units, which allowed data to be transmitted hourly to a server computer at DNR. Sondes were deployed inside vertically-oriented four-inch diameter PVC pipes with several two-inch holes drilled along their length to allow for water exchange. Depending on location, sondes were either suspended from a float 1.0-meters below surface or fixed 0.3-meters or 0.5-meters above bottom resting on a stop bolt.
Sondes at the following stations were deployed at a fixed depth of 0.3 meters above the bottom: XDB4544 (Blossom Pt), XDM4486 (Bishopville Prong), XKH2797 (Carpenters Point), XGG6667 (CBEC), XFB0231 (Fenwick), XKH0375 (Susquehanna Flats), WXT0013 (Iron Pot Landing), PXT0455 (Jug Bay), XGG8359 (Kent Narrows Inside), XGG8458 (Kent Narrows Outside), LMN0028 (Little Monie Creek), XEA3687 (Mattawoman), MTI0015 (Mataponi), NPC0012 (Newport Creek), XJG7035 (Otter Point Creek), XFB2184 (Piscataway), XDC3807 (Popes Creek), XHH4931 (Possum Point - Bottom), XDB8884 (Port Tobacco), XBM8828 (Public Landing), XHH4916 (The Sill), XCC8346 (Swan Pt.), TUV0021 (Turville Creek), and XCC9680 (Wicomico Beach).
Sondes at the following stations were deployed at a fixed depth of 0.5 meters above the bottom: XCD5599 (Breton Bay), ZDM0001 (Harness Cr. Downstream), ZDM0002 (Harness Cr. Upstream), XDE4587 (Pin Oak), XBE8396 (Piney Point), and XBF7904 (St Georges Creek).
All other sondes were deployed suspended from a buoy at a depth of 1.0 meter below the surface. At two stations, XHH4916 and XHH4931, sondes were deployed at two depths.
WATER QUALITY CALIBRATION SAMPLES:
Each time sondes were exchanged at each Continuous Monitoring station, "Grab" water quality samples were collected at meter depth using a horizontal "Alpha" water sampler. At the time the water was collected, a HydroLab sonde measurement was taken 1.0 meter depth.
Numbered two-quart bottles were triple-rinsed and filled with water for "whole" and "filtered" nutrient and chlorophyll samples.
Nutrient, pigment and suspended-solid water samples were filtered on station or shortly thereafter. Sample waters and filters were placed on ice immediately after filtration.
Particulate samples included: Chlorophyll, Particulate Carbon, Particulate Nitrogen, Particulate Phosphorus (PP), Particulate Inorganic Phosphorous (PIP), Total Suspended Solids (TSS) and Volatile Suspended Solids (VSS).
Filtrate collected from TSS/VSS or PP/PIP filtrations was used for dissolved nutrient samples. Total Dissolved Nitrogen and Total Dissolved Phosphorus, Nitrate, Nitrite, Ammonia, Orthophosphate, Silicate and Dissolved Organic Carbon samples were collected.
HYDROLAB PROFILE:
The first reading of the HydroLab water-column profile at each station was recorded at the same time the water quality "grab" sample was collected. After the 1.0-meter depth record was logged, the sonde was lowered to the bottom. A reading was taken at 0.3-meters above the bottom. The sonde was raised and measurements were recorded at 0.5-meter or 1.0-meter increments until it reached the surface. (In cases where station depth was greater then 3-meters, the sonde was raised in 1-meter increments).
SECCHI DEPTH:
Secchi Disk Depth was measured each time sondes were exchanged. Readings with the secchi disk were made in-situ without the aid of sunglasses. The secchi disk was lowered into the water, on the shady side of the boat or pier. The depth at which the disk was no longer visible was recorded. The time at which the reading was taken was noted. This facilitated later matching of secchi depth readings with transmissometer and turbidity data.
PAR MEASUREMENT:
Underwater Photosynthetically Active Radiation (PAR, 400-700nm)
When meters were exchanged at a site, down-welling light penetrating the water column (PAR) was measured underwater at several depths to calculate the light attenuation coefficient, Kd. Simultaneous surface and submersed PAR intensity measurements were taken to account for variability in incident surface irradiance due to changes in cloud cover. Data collected from this procedure were used to estimate the depth of the photic zone.
The equipment used was manufactured by LI-COR, Inc. and consisted of a LI-192SA, flat cosine Underwater Quantum Sensor, a LI-190SA air (deck) reference sensor and a Data Logger (LI-1000 or LI-1400).
Surface and underwater readings were recorded simultaneously. Readings were allowed to stabilize before being recorded. If the station depth was less than 3 meters, readings were taken at 0.1 meter and at 0.25-meter intervals until 10% for the 0.1-meter reading was reached. If the station depth was greater than 3 meters, a reading was taken at 0.1-meter and at 0.5-meter intervals until 10% of the 0.1-meter reading was reached.
SONDE DATA CHECKS
The continuous monitoring sondes were retrieved, calibrated and replaced bi-weekly from January to December. At each deployment, sondes were replaced with clean, recalibrated units and data from the data loggers were downloaded to a computer.
In the field, before an instrument was replaced, field staff allowed both the new (freshly calibrated) sonde and the old (deployed) sonde to log two readings (fifteen minutes apart) side by side at the same depth. In addition, for one of the readings, data were recorded from a discrete instrument -usually a HydroLab sonde. This three-way comparison assured that the "new" and "old" sondes were both reading each parameter within a certain tolerance. The HydroLab reading was used as a "double-check," and since it was a discrete reading, it allowed staff to watch the display and note whether the parameters were fluctuating or stable.
EcoWatch(tm) software (a YSI product) was used to calibrate the instruments as well as to upload and view data collected. Data downloaded from the sonde were subjected to quality assurance/quality control checks to ensure that values outside the range of possibility were not displayed on the DNR web site.
Data were evaluated using both three-way in-situ comparison results and data from sonde calibrations. The comparison tolerances were as follows - for both pre- post- calibration and in-situ comparisons: Temperature (deg C) +- 0.2; Specific Conductance (uM/cm) +- 5%; Dissolved Oxygen (mg/l) +- 0.5 mg/l; pH +- 0.2; Turbidity (NTU) +- 5%; Chlor +- 5%.
Excessive drift between pre- and post- calibration values of sonde probes, variance from in-situ measurements or probe failures caused data to be flagged. When post-calibration drift exceeded the limits stated above in both the post-calibration and the in-situ comparables, the "bad data" were masked within the data set with an error code (see QAPP for list of error codes).
SONDE FILE POST-PROCESSING:
Each "raw" .csv file of sonde data was post-processed using an Excel(tm) Macro. The file was opened and renamed. Rows of data acquired before and after deployment were deleted. Records (if any) were also deleted if instrument error codes indicated "garbage" data. The macro rearranged columns and inserted error-tracking columns and headings. Macro statements flagged negative values, missing values and highlighted values outside each parameter's normal range. The macro also returned a report summarizing range exceedances. Event and instrument information was appended to each record.
Flagged values were evaluated. Common anomalies included spikes in fluorescence and turbidity, dips in specific conductance, and extremely high dissolved oxygen readings. Instrument post-calibration results, in-situ comparisons with HydroLab, LI-COR readings, historical data from near-by locations and survey crew remarks were used to determine whether sensor values were acceptable.
In cases where data were determined to be unreliable, the reason(s) were documented with error codes and comments. Unreliable data were masked. No data were discarded. Only data considered reliable were published in reports.
Field staff and Tawes Office staff reviewed continuous monitoring data weekly. If a problem was identified, a field team member was dispatched to replace the instrument as soon as possible.
VERIFICATION AND DATA MANAGEMENT
At the end of the monitoring season, DNR Tawes Office and Field Office personnel conducted additional data QA/QC procedures. All of the data were plotted and outliers and anomalous values were thoroughly researched. Staff compared unusual values to historic values from the site and values from nearby sites in the Bay. Weather events were considered, event logs were reviewed and field staff were consulted regarding possible legitimate causes for the values. In cases where values were not considered legitimate, error codes were assigned. All data were retained in the archive data set. After field staff and the Quality Assurance Officer reviewed error flags, the values were masked within the published dataset.
Further information about laboratory analytical procedures may be obtained from the "Process_Contact".
Further information about laboratory analytical procedures may be obtained from the "Process_Contact".
The data are contained in five related entities (tables): Station_Information, Monitoring_Event_Data, Water_Quality_Data, Light_Attenuation_Data and CMON_DATA. Each table contains attributes (fields).
The entity Station_Information is comprised of the attributes: STATION, DESCRIPTION, WATER_BODY, CBP_BASIN, TS_BASIN, BASIN, CBSEG_2003, CBSEG_2003_DESCRIPTION, HUC8, CATALOGING_UNIT_DESCRIPTION, HUC11, WATERSHED, FIPS, STATE, COUNTY/CITY, FALL_LINE, LATITUDE, LONGITUDE, LL_DATUM, UTM_X and UTM_Y
The entity Monitoring_Event_Data is comprised of the attributes: EVENT_ID, SOURCE, AGENCY, PROGRAM, PROJECT, STATION, EVENT_START_DATE, EVENT_START_TIME, CRUISE, TOTAL_DEPTH, UPPER_PYCNOCLINE, LOWER_PYCNOCLINE, AIR_TEMP, WIND_SPEED, WIND_DIRECTION, PRECIP_TYPE, TIDE_STAGE, WAVE_HEIGHT, CLOUD_COVER, GAGE_HEIGHT, PRESSURE, FLOW_STAGE, DETAILS and WATER_BODY.
The entity Water_Quality_Data is comprised of the attributes: EVENT_ID, SOURCE, PROJECT, STATION, SAMPLE_DATE, SAMPLE_TIME, DEPTH, LAYER, SAMPLE_TYPE, SAMPLE_ID, PARAMETER, QUALIFIER, VALUE, UNIT, METHOD, LAB, PROBLEM, DETAILS, TOTAL_DEPTH, UPPER_PYCNOCLINE, LOWER_PYCNOCLINE, LAT, and LONG.
The entity Light_Attenuation_Data is comprised of the attributes: EVENT_ID, SOURCE, PROJECT, STATION, SAMPLE_DATE, SAMPLE_TIME, SAMPLE_REPLICATE_TYPE, DEPTH, EPAR_S, EPARU_Z, EPARD_Z, UNIT, METHOD, DETAILS, WATER_BODY, TOTAL_DEPTH, UPPER_PYCNOCLINE, and LOWER_PYCNOCLINE.
The entity CMON_DATA is comprised of the attributes: DATE, TIME, DEPTH, DISSOLVED OXYGEN, PERCENT OXYGEN SATURATION, SALINITY, TEMPERATURE, PH, TURBIDITY AND CHLOROPHYLL.
The most current version of the Water Quality Data Dictionary - Online may be found at: [<http://archive.chesapeakebay.net/data/data_dict.cfm?DB_CODE=CBP_WQDB> ].
Quality Assurance Project Plan for the Maryland Department of Natural Resources, Chesapeake Bay Shallow Water Quality Monitoring Program, for the period July 1, 2007 - June 30, 2008. [<http://mddnr.chesapeakebay.net/eyesonthebay/documents/swm_qapp_2007_draft.pdf>]