Two surveys were required to map the Nanticoke and Pocomoke Rivers. Data collected during Upper and Lower Nanticoke River surveys were combined. Similarly, data collected during the Upper and Lower Pocomoke River surveys were combined. Normally, upper and lower surveys were conducted on the same day. The upper and lower legs of the May Nanticoke and Pocomoke surveys and the July Pocomoke survey occurred one day apart due to weather conditions.
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 up 45 km/hr (24.3 kts). 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. Corsica River surveys were conducted using a second sonde equipped with blue-green algal (phycoerythrin) sensors used to measure blue green algal cells/ml and Relative Fluorescence Units (RFUs). Water depth was also measured. The DATAFLOW system sampled water at approximately 0.5-m depths below the surface.
Additional water-quality measurements were made at thirty-five calibration stations. Secchi disk depth, HydroLab (water temperature, pH, dissolved oxygen, specific conductance, and salinity) and photosynthetic active radiation measurements were made at five stations during each survey.
Water-quality calibration chlorophyll and total suspended solids "grab" water samples were collected at five stations during each monthly mapping survey. The "grab" samples were collected, after stopping the boat, at 0.5-m depth and filtered, when possible, on site. A suite of nutrient "grab" water samples were also collected monthly at Corsica River stations: COR0056, XHH3851, XHH4528, XHH4916 and XHH4931. The Corsica survey was the only water quality mapping survey on which nutrient samples were collected.
Laboratory analyses were performed on calibration "grab" sample water. Concentrations of chlorophyll a and total suspended solids were determined for all stations. Corsica River stations were also analyzed for total dissolved nitrogen, particulate nitrogen, nitrite, nitrite + nitrate, ammonium, total dissolved phosphorus, particulate phosphorus, orthophosphate, dissolved organic carbon, particulate carbon and volatile suspended solids.
Water quality mapping provides data on variability and patchiness that are 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 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 three 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://archive.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, 2013 - June 30, 2014. <http://mddnr.chesapeakebay.net/eyesonthebay/documents/SWM_QAPP_2013_2014_FINAL.pdf>
Guide to Using Chesapeake Bay Program Water Quality Monitoring Data,EPA 903-R-12-001, February 2012, CBP/TRS 304-12 <http://www.chesapeakebay.net/documents/3676/wq_data_userguide_10feb12_mod.pdf>
NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 8.0.0.0.0 <online: <http://gcmd.gsfc.nasa.gov/learn/keywords.html>
The Nutrient Analytical Services Laboratory (NASL) at the Chesapeake Biological Laboratory (University of Maryland) analyzed chlorophyll, 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, and the National Atmospheric and Oceanic Administration Chesapeake Bay Program Office.
MD DNR followed specific procedures to ensure that the DATAFLOW component of the Shallow Water Quality Monitoring Program project design was properly implemented and managed with sufficient accuracy, precision and detection limits. Accuracy (closeness to the true value) of collected data was controlled and assured by the proper use, calibration and maintenance of both field and laboratory equipment used for the measurement of physical and chemical parameters.
YSI 6600 V2 sondes were configured with the following probes: 6025 (chlorophyll); 6136 (turbidity); 6560 (spCond & temperature); 6561(pH); and 6150ROX (dissolved oxygen) during 2013. A second sonde configured with 6132 (blue-green phycoerythrin) probe was also used (Corsica surveys only). Resolution, range and accuracy specifications for the sonde and probes may be obtained from the manufacturer <http://www.ysi.com/accessories.php> - Sensors&Probes - 6-Series.
Procedures used to control and assure the accuracy of field measurements included: calibration of field instruments, verification of calibration results, 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. Water quality calibration-station laboratory analytical results were used to crosscheck 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 analytical accuracy.
Accuracy of Chesapeake Biological Laboratory, Nutrient Analytical Services Laboratory (CBL NASL) 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. Analytical results were compared using appropriate statistical tests 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 participated two times in 2013 in the United States Geologic Survey (USGS) Standard Reference Sample Project.
OTHER ATTRIBUTE ACCURACY INFORMATION
May 2013 High sonde dissolved oxygen, fluorescence and TCHL_PRE_CAL values were measured during the Corsica survey. Algal sample counts and laboratory results for chlorophyll a were also high.
August 2013 Post calibration results for the chlorophyll probe used on the Upper Pocomoke survey were outside the range of normal values on the high end (9%). Post calibration results for the pH probe used on the Big Annemessex were outside the range of normal values.
May 2013 The Corsica survey cruise track was altered from the normal route in order to collect a sample for another project. If multiple surveys are required to map a water body, the surveys are performed on the same day whenever possible. Due to heavy weather, the Upper Nanticoke survey was conducted on 7-May-2013 and the Lower Nanticoke survey was conducted on 8-May-2013. The Upper Pocomoke survey was conducted on 7-May-2013 and the Lower Pocomoke survey was conducted on 8-May-2013.
July 2013 The Upper Pocomoke survey was conducted on 11-Jul-2013 and the Lower Pocomoke survey was conducted on 12-Jul-2013 for logistical reasons.
October 2013 The cruise track of the Corsica survey was altered from the normal route in order to collect a sample for another project.
Sampling-event, water-quality-calibration, pigment and suspended solids data from thirty-five stations are included in the dataset. Five calibration samples were collected during each of the following monthly sampling runs: Big Annemessex, Corsica, Lower Nanticoke, Lower Pocomoke, Manokin, Upper Nanticoke, and Upper Pocomoke.
Beginning in January 2010, a full suite of nutrient samples was no longer collected during most Water Quality Mapping Surveys. The exception was the Corsica River surveys, where, during 2013, full nutrient suites continued to be collected at stations: COR0056, XHH3851, XHH4528, XHH4916 and XHH4931.
Samples from the five calibration stations on the Corsica River were collected and analyzed for the same suite of nutrients as those measured for the Chesapeake Bay Mainstem Program (chlorophyll a, pheophytin, total dissolved nitrogen, particulate nitrogen, nitrite, nitrite + nitrate, ammonium, total dissolved phosphorus, particulate phosphorus, orthophosphate, particulate carbon, total suspended solids and volatile suspended solids) plus particulate inorganic phosphorus.
Contour maps based on 2013 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>.
Data users may discover a few interruptions in sonde datasets. These were related to short-term problems with flow, power or sonde operation.
Turbidity data were censored in cases where bottom sediment disturbances were determined to be caused by the sampling vessel or other vessels.
April 2013 Sea conditions were too rough for LICOR sampling at station XBI7962 on the Manokin survey. A software problem resulted in a data gap between 09:51 and 09:54 on the Big Annemessex run. Fathometer data were not measured during the Lower Nanticoke, Lower Pocomoke and Upper Pocomoke surveys. Fluorescence and chlorophyll (calculated) data were not acquired on the Upper Pocomoke due to probe failure.
May 2013 A broken unit precluded LICOR sampling at stations: POK0316, POK0232, POK0187 and POK0087 on the Upper Pocomoke survey. Sonde data were not collected between 09:09 and 09:20 on the Manokin run for unknown reasons. There was a battery power issue between 09:26 and 09:35 when sampling the Lower Nanticoke. Fathometer data were not measured during the Upper Nanticoke and Lower Pocomoke surveys.
June 2013 Fathomer readings were not recorded during the Corsica survey due to a software configuration problem. A broken unit resulted in no LICOR samples at Manokin stations: XBI6387, ET8.1, XBJ9344 and MNK0146 as well as Upper Nanticoke stations: XEJ2464, XEJ0543, XDJ8905, XDJ6207 and XDI4990. Rough conditions prevented LICOR sampling at Lower Pocomoke stations: XAJ5327, XAJ7035 and XAJ8271. A gap in data between 11:32 and 12:04 was due to sonde battery failure.
July 2013 No LICOR samples were collected at Manokin stations XBI7962 and XBI6387 due to sea conditions.
August 2013 LICOR data were not collected on the Upper Nanticoke survey for unspecified reasons. LICOR data were not collected on the Upper Pocomoke run because of a malfunctioning LICOR unit. Power failures resulted in two data gaps during the Manokin run.
September 2013 LICOR readings were not taken on the Manokin survey at stations: XBJ9344 and MNK0146. Sonde battery failure resulted in a data gap between 10:04 and 10:13 on the Lower Pocomoke run.
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 a 6560 conductivity/temperature probe, a 6136 turbidity probe, a 6025 chlorophyll probe, a 6561 pH probe, a 6150ROX (Optical) Dissolved Oxygen probe and in one case, a 6132 (blue-green phycoerythrin) probe, were maintained and calibrated before and after each deployment in accordance with YSI recommendations. <http://www.ysi.com/resource-library.php>
CONTINUOUS SURFACE WATER QUALITY MAPPING:
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, and 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. The system was configured with conductivity/temperature, turbidity, chlorophyll, pH and dissolved oxygen probes. The sonde transmitted data sensor measurements to a YSI 650 data logger.
Positioning and depth instrumentation consisted of a Raymarine A70D Chartplotter/Sounder. The data logger matched the position data with water-quality sensor data for each observation. The Raymarine A70D 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 were 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 water body 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.
"Grab" samples were collected at the same time as the HydroLab surface sample was recorded. Numbered two quart bottles were triple-rinsed and filled with water for chlorophyll and total suspended solids samples and, on the Corsica River survey, "whole" and "filtered" nutrient samples.
Nutrient, chlorophyll 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, Phaeophytin, 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. Nitrate, Nitrite, Ammonia and Orthophosphate 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 bottle 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 turbidity probe 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 using 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% of 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.
Each raw .txt file, created by DATAFLOW/LabView during 2013 mapping cruises on all water bodies was post-processed in the following manner.
Each file was opened in Microsoft Excel(tm) 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, negative values were flagged, and values outside each parameter's normal range were highlighted. The macro also returned a form summarizing exceedances. Finally, mapping cruise event and instrument information were appended to each record. Flagged values were evaluated for common anomalies including 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.
MERGING PRIMARY AND SECONDARY SONDE DATA
When a second data sonde was used on a survey, it was necessary to generate time adjustment values because the clocks in the two sondes were not synchronized. Secondary sonde adjusted times made it possible to merge secondary sonde data with data from the primary sonde. Adjustment values for 15,531 records were derived using expressions which shifted the time. The mean time adjustment was 0.97 seconds and a small number of three second adjustments were needed.
University of Maryland's Chesapeake Biological Laboratory (CBL), Nutrient Analytical Services Laboratory (NASL) analyzed chlorophyll, phaeophytin, total dissolved nitrogen, particulate nitrogen, nitrite, nitrite + nitrate, ammonium, total dissolved phosphorus, particulate phosphorus, particulate inorganic phosphorus, orthophosphate, particulate carbon, total suspended solids, and volatile suspended solids.
Further information about laboratory analytical procedures may be obtained from the "Process_Contact".
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 members were consulted regarding possible legitimate causes for outlying values. In cases where values were not considered to be legitimate, they were masked from the published dataset with the approval of the field staff and the Quality Assurance Officer.
The data are contained in six related entities (tables): Station_Information, Monitoring_Event_Data, Water_Quality_Data, Light_Attenuation_Data, SONDE_DATA and BGA_DATA. Each table contains attributes (fields). NOTE: SONDE_DATA and BGA_DATA were not served by the Chesapeake Bay Program at the time this metadata record was developed.
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 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.
Cyanobacteria are commonly referred to as Blue Green algae (BGA). YSI 6600 sondes are not configured with enough sensor ports to measure water quality and Cyanobacteria with a single instrument so two sondes are used. Cyanobacteria sonde data merged with primary sonde data by matching record timestamps as closely as possible.
The entity BGA_DATA is comprised of the attributes: bgaTemp, bgaSpCond, BGA_PE_Conc, BGA_PE_RFU, bgaDate, bgaTime, bgaTimeAdjusted, 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 viewed and downloaded from <http://mddnr.chesapeakebay.net/sim/dataflow_data.cfm>.
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, 2013 - June 30, 2014. <http://mddnr.chesapeakebay.net/eyesonthebay/documents/SWM_QAPP_2013_2014_FINAL.pdf>
Guide to Using Chesapeake Bay Program Water Quality Monitoring Data,EPA 903-R-12-001, February 2012, CBP/TRS 304-12 <http://www.chesapeakebay.net/documents/3676/wq_data_userguide_10feb12_mod.pdf>