Multiple surveys were required to map several of the larger water bodies. Data acquired during two surveys were combined to map the Eastern Bay and Miles and Wye Rivers. Upper and Lower legs of the Chester River were sampled. Mapping data acquired during four Choptank River surveys were combined. Each month, Potomac River mapping surveys combined data collected on nine sections of the Potomac and St. Mary's Rivers and Breton and St. Clement's Bays.
Water quality mapping was conducted using DATAFLOW, a compact, self-contained surface water quality mapping system deployed in a small boat operating at planing speeds of 46 km/hr (25 kts) or less. Measurements were made approximately every four seconds or 30 meters (100 feet). Seven water quality parameters were measured: water temperature, salinity, conductivity, dissolved oxygen, turbidity, fluorescence and pH as well as water depth. The DATAFLOW system sampled water at approximately 0.5-m depths below the surface.
Additional water-quality measurements were made at one hundred and twenty-five calibration stations. During each mapping cruise, "grab" samples were collected at between six and eight stations per water body segment. Calibration samples were collected, after stopping the boat, at 0.5-m depth and filtered on site. Secchi depth, HydroLab and photosynthetic active radiation measurements were taken at the same time.
Laboratory analyses were performed on calibration samples. Chlorophyll a, total dissolved nitrogen, particulate nitrogen, nitrite, nitrite + nitrate, ammonium, total dissolved phosphorus, particulate phosphorus, orthophosphate, dissolved organic carbon, particulate carbon, silicic acid, total suspended solids, volatile suspended solids, and turbidity values were determined.
Water quality mapping provides data on variability and patchiness that is valuable in assessing water quality criteria, and in determining attainment of those criteria. For example, spatial information on turbidity can be correlated to the spatial coverage of living resources such as bay grasses - Submerged Aquatic Vegetation (SAV). This information can be used to determine and assess water clarity criteria necessary to support SAV growth, address the progress of meeting SAV restoration goals, and target specific locations for SAV restoration.
Spatially intensive data can also help pinpoint localized areas of water quality concern, such as areas of low dissolved oxygen that can cause fish kills, and their possible links to nearby land uses or point sources.
Water quality maps can capture localized areas of algae blooms, high turbidity, or low dissolved oxygen that may adversely affect living resources in shallow water habitats and spawning areas.
Spatial data can also be aggregated across watershed units to aid in the evaluation of entire systems. Water quality mapping data are 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> ]. An online version of the Data Dictionary is also available. [<http://www.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, 2006 - June 30, 2007. [<http://mddnr.chesapeakebay.net/eyesonthebay/swm_qapp_2006.pdf> ]
The Maryland Department of Mental Health and Mental Hygiene (DHMH) analyzed pigments and turbidity samples. The Nutrient Analytical Services Laboratory (NASL) at the Chesapeake Biological Laboratory (University of Maryland) analyzed nutrient and suspended solids samples.
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, and the National Atmospheric and Oceanic Administration Cooperative Institute for Coastal and Estuarine Environmental Technology.
YSI 6600 sondes were configured with the following probes: 6560, 6562, 6025, and 6136. Resolution, range and accuracy specifications for the sonde and probes may be obtained from the manufacturer. <http://www.ysi.com/environmental-monitoring/data-acquisition.htm>
The procedures to control and assure the accuracy of field measurements involved the calibration of field instruments, the verification of calibrations, equipment maintenance, and collection of filter blanks. Most of the details of how data acquired with YSI sondes were quality assured and quality controlled are described in process description elements in the Lineage portion of this metadata record. The results of the water quality attributes analyzed in the laboratories were also used to calibrate and crosscheck the sonde data for accuracy.
PAR sensors were returned to LICOR, Inc. prior to the field season for factory calibration.
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.
The fluorescence probe used on the June 2006 Corsica, Choptank Tributaries, Mid Choptank mapping surveys was 6% out of range when post calibrated. The fluorescence probe used on the June 2006 Lower Choptank, Upper Choptank and Little Choptank surveys was 12% out of range when post calibrated. The fluorescence probe used on the July 2006 South River and Miles/Wye surveys was 7% out of range when post calibrated.
The dissolved oxygen probe used on the July 2006 Choptank Tributaries survey was 37% out of range when post calibrated. When the dissolved oxygen probe used on the August 2006 Eastern Bay survey was post calibrated, it was found to be 15% out of range. The dissolved oxygen probe used during the September 2006 Corsica survey was out of range by 6% when post calibrated. The dissolved oxygen probe used during the September 2006 Potomac Upper Oligohaline survey was found to be 15% out of range when post calibrated. The dissolved oxygen probe used on the October 2006 Upper Choptank mapping survey was out of range by 7% when post calibrated.
The pH probe used on the October Upper Chester fluctuated within a +/- 0.15 range during post calibration.
The Turbidity probe used during the Mid Choptank and Wicomico surveys was off by 8% when post calibrated.
Finally, BOAT_SPEED and TOTAL_DEPTH values listed in the DFLOW_DATA table are not considered reliable and should be used only with great caution.
No calibration samples were collected at station ZDM0001 because a pile driver prevented access to the station.
Cruise tracks were modified due to heavy weather conditions during the following surveys: June 2006 South River, Potomac Upper Oligohaline and Piney Point; August 2006 Potomac Upper Oligohaline; October 2006 Lower Chester and Potomac Upper Oligohaline.
MEASURED_DEPTH values acquired by the DATAFLOW instrumentation are inherently inaccurate due to a variety of issues associated with using depth sounders while moving at high speeds. The data should be used with caution and validated with additional data sources. Depth values greater than 100 m. are masked within the data set.
Sampling-event and water-quality-calibration pigment, nutrient and suspended solid data from eighty-eight stations are included in the dataset. Samples were collected at thirteen sites on the Chester River and twelve on the Patuxent. Eight sites were sampled on the St. Mary's River and seven sites on the Wye and Miles Rivers. Six sites were sampled on each of the following rivers: Bush, Gunpowder, Little Choptank, Middle, Rhode/West, and South Rivers. Samples were also collected at six sites during surveys of Eastern Bay and Fishing Bay.
Contour maps based on 2005 Dissolved Oxygen, Salinity, Turbidity, Temperature and Chlorophyll data acquired during DATAFLOW monthly mapping cruises are available on-line. [<http://mddnr.chesapeakebay.net/sim/dataflow_data.cfm>]
The user will note a relatively large number of missing values in the Patuxent sonde data subset. Due to instrumentation and configuration issues, sonde data acquired during the 2005 Patuxent mapping cruises required manual preparation before they could be post-processed. (See preparation step in DATAFLOW FILE POST-PROCESSING procedure described in next section of this metadata record).
The user may discover a few interruptions in sonde datasets. These interruptions were related to short-term problems with flow or sonde operation.
All other missing attribute values were masked because the data were determined to be unreliable during the quality control process.
YSI 6600 data sondes equipped with 6562 DO probe, a 6560 conductivity/temperature probe, a 6136 turbidity probe, and a 6025 chlorophyll probe were maintained and calibrated before and after each deployment in accordance with YSI recommendations. <http://www.ysi.com/environmental-monitoring/data-acquisition.htm>
CONTINUOUS SURFACE WATER QUALITY MAPPING:
DATAFLOW Mapping System DATAFLOW is a compact, self-contained surface water quality mapping system, suitable for use in a small boat operating at planing speeds of about 25 knots. The system collects water through a pipe ("ram") deployed on the transom of the vessel, pumps it through an array of water quality sensors, then discharges the water overboard. Orientation of the sonde vertically, with probes upward, ensures that no air bubbles are conveyed to the sensors, preventing errors that might be caused by such bubbles.
Water quality instrumentation consisted of a YSI 6600 Sonde equipped with a flow-through chamber. Sensors included a Clark-type YSI 6562 DO probe, a YSI 6560 conductivity/temperature probe, a 6136 turbidity probe, and a 6025 chlorophyll probe. The sonde transmitted data collected from the sensors to a YSI 650 data logger.
Positioning and depth instrumentation consisted of a Garmin GPS/MAP 168 Sounder. The data logger matched the position data with water-quality sensor data for each observation. The Garmin 168 GPS transmitted NMEA data to a small form factor computer. A DATAFLOW/Labview program was used to merge position and depth data with data collected by the logger and create an output file.
The system was equipped with an inline flow meter. Although the flow rate did not affect sensor readings, decreased flow was an indication of either a partial blockage or an interruption of water flow to the instrument. Flow data was used in the field as a diagnostic tool to ensure that the system was working properly and later, as a quality assurance tool, to verify that water flow was uninterrupted. A boat horn was wired to the flow meter. If the flow-rate fell below 3.0 l s-1, the horn sounded and warned operators that a problem needed to be corrected.
Cruise tracks varied depending on the water body being mapped. In general, a square-wave pattern was followed by alternately sampling shallow shoreline areas, and open, deeper waters while traveling up and down river. Alternative cruise paths were followed if tributary size, shape impediments, or obstructions dictated otherwise. Cruise patterns were selected to obtain representative coverage of shallow water habitats and open waters so that segment-wide criteria could be assessed as accurately as possible. Navigational issues and placement of representative calibration sites also determined ultimate cruise tracks.
WATER QUALITY CALIBRATION SAMPLES:
At each calibration station, "grab" water quality samples were collected from the outflow of the DATAFLOW unit.
The samples were collected at the same time the HydroLab surface sample was recorded. 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 Calibration station was recorded at the same time the water quality "grab" sample was collected. The first HydroLab record logged was for the 0.5-meter depth. The sonde was then 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 than 3-meters, the sonde was raised in 1-meter increments).
SECCHI DEPTH:
Secchi Disk Depth was measured at each Calibration station. 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, and the depth at which it was no longer visible was recorded. The Secchi depth reading was taken near the stern of the vessel and the time at which the reading was taken was noted (to the second) from the Global Positioning System. This facilitated later matching of Secchi depth readings with transmissometer and turbidity data.
PAR MEASUREMENT:
Underwater Photosynthetically Active Radiation (PAR, 400-700nm)
At each Calibration station, down-welling light penetrating the water column (PAR) was measured underwater at several depths to calculate the light attenuation coefficient, Kd. Simultaneous deck 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).
Deck 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.
DATAFLOW FILE POST-PROCESSING:
Each raw .txt file, created by DATAFLOW/LabView during 2006 mapping cruises on all other water bodies was post-processed in the following manner.
Each file was opened in Excel and renamed. Rows of data acquired before and after mapping were deleted. Records (if any) were also deleted if they did not have associated GPS values. A macro was executed that rearranged columns and inserted error-tracking columns and headings. Next, a macro was run that flagged negative values, missing values and highlighted values outside each parameter's normal range. The macro also returned a report summarizing exceedances. Mapping cruise 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 nearby 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 "bad" were documented with error codes and comments. Unreliable data were masked. No data were discarded. All DATAFLOW data for each mapping cruise; both good and "bad", were retained in an archival file. Only data considered reliable were published in reports.
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 water quality calibration "grab" sample data were plotted. 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 from the published dataset with 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 SONDE_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.
++++++++++++++++++++ DRAFT -TO BE DETERMINED when data are served by Chesapeake Bay Program
The entity SONDE_DATA is comprised of the attributes: SAMPLE_DATE, SAMPLE_TIME, WATER_BODY, SECTION, PRI_SEG, SONDE, LATITUDE, LONGITUDE, TOTAL_DEPTH, BOAT_SPEED, BATT, WTEMP, SPCOND, SALINITY, DO_SAT, DO, PH, TURB_NTU, FLUOR, TCHL_PRE_CAL and COMMENTS.
+++++++++++++++++++++
Maps created by interpolating the Dissolved Oxygen, Turbidity, Chlorophyll a, Salinity and Temperature data acquired during mapping cruises may be downloaded from <http://mddnr.chesapeakebay.net/sim/dataflow_data.cfm>
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>]