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 2006 state of forty-four 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>
Quality Assurance Project Plan for the Maryland Department of Natural Resources Chesapeake Bay Shallow Water Quality Monitoring Program for the period July 1, 2006 - June 30, 2007 <http://mddnr.chesapeakebay.net/eyesonthebay/documents/swm_qapp_2006.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, Harford County Maryland and Anne Arundel County Maryland.
The YSI 6600 sondes were configured with the following probes: 6560, 6562, 6025, 6132, and 6136. Resolution, range and accuracy specifications for the sonde and probes may be obtained from the manufacturer. https://www.ysi.com/DocumentServer/DocumentServer?docID=EMS_E54
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 2006, 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 2006 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.
Grab samples collected in late August 2006 and throughout September 2006 were filtered using baked PP/PIP filter pads. When processed, the sample processing protocol followed was for unbaked PP/PIP pads. Therefore results for NH4, PO4, NO23, Silica, TDN/P and DOC may have been affected.
The 2006 Continuous Monitoring project dataset includes twelve months of sonde records from the continuous monitoring sites named Iron Pot Landing, Jug Bay, Mataponi and Sycamore Point. The sonde at the Otter Point creek site was deployed eleven months. Sonde data were collected for ten months at the Sandy Point East and SERC sites. Nine month deployments occurred at Casson Point, Gary's Creek, Lauderick Creek and Sandy Point South. Deployments at Beard's Creek, Betterton, CBEC, Fenwick, Fort McHenry, Georgetown Yacht Basin, Hambleton Point, High Banks, Jamaica Point, Kent Point, Mattawoman Creek, Pin Oak, Piscataway, Pope's Creek, Rolph's Wharf, Shady Side, and Wicomico Beach lasted eight months. Sondes were deployed seven months at Breton Bay, Deep Landing, Mulberry Point, Piney Point, Possum Point - Bottom, Possum Point - Surface, St George's Creek, Swan Point, The Sill Bottom, and The Sill Surface. The sondes at Emory Creek, Horn Point Lab, Upper Ferry and Whitehaven were deployed six months and the sondes at Blossom Point, Harness Creek Downstream, Harness Creek Upstream were deployed five months. Finally, the sonde at Little Monie Creek was deployed for four months.
A sonde was deployed at Emory Creek beginning 1-Jan-06 until 22-Jun-06 when it was removed and deployed at the Possum Point site.
The Blossom Point site was damaged and the sonde was lost during heavy weather associated with Tropical Storm Ernesto in the first days of September 2006.
The user may discover a few interruptions in sonde datasets. In most cases, these interruptions were related to short-term problems with sonde operation.
Sonde data were not acquired at station XGE3275 between 2-Aug-06 and 18-Aug-06 due to a logging error. Fifteen minute increment sonde data were not recorded at station WXT0013 between 23-Apr-06 and 4-Apr-06 due to a logging error. However, hourly data for station WXT0013 between 23-Apr-06 and 4-Apr-06, captured via satellite telemetry, were recovered.
On a few occasions, due to extreme low tide conditions, sondes were not submerged. These data are not included in the published dataset.
High water temperatures in July and August 2006 contributed to heavy fouling of Dissolved Oxygen probes in some locations. Dissolved Oxygen data were deleted in cases where post-calibration was out of range.
All other missing sonde attribute values were removed because the data were determined to be unreliable during the quality control process.
Extra grabs samples were accidentally collected 6-Nov-06 at station XJG7035 and 13-Nov-06 at stations: MTI0015, WXT0013 and PXT0455. The bottom layer DOC 27-Oct-06 sample for Station XHH4916 was not acquired due to inadequate sample water and filtrate volume. Nutrient and sediment samples were not collected station at station XJG7035 on 4-Dec-06 due to extreme low water conditions. Grab samples were only collected April through October 2006 at station XGE3275.
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. Eighteen 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 stop bolt.
Sondes at the following stations were deployed at a fixed depth of 0.3 meters above the bottom: LMN0028, MTI0015, PXT0455, TUV0021, WXT0013, XCC8346, XCC9680, XDB4544, XDC3807, XEA3687, XFB0231, XFB2184, XGG6667, XHH4916, XHH4931, and XJG7035. Sondes at the following stations were deployed at a fixed depth of 0.5 meters above the bottom: XBE8396, XBF7904, XCD5599, XDE4587, ZDM0001,and ZDM0002. 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 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 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 instructions flagged negative values, missing values and highlighted values outside each parameter's normal range. The macro also returned a report summarizing 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, 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) values were determined to be unacceptable 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 legitimate, they were masked within the published dataset with an error code and the approval of the field staff and the Quality Assurance Officer.
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: Dissolved Oxygen, percent Oxygen Saturation, Salinity, Temperature, pH, Turbidity and Chlorophyll.
Quality Assurance Project Plan for the Maryland Department of Natural Resources Chesapeake Bay Shallow Water Quality Monitoring Program for the period July 1, 2006 - June 30, 2007 <http://mddnr.chesapeakebay.net/eyesonthebay/swm_qapp_2006.pdf>