Choosing, Installing, Calibrating, and Maintaining Stream Monitoring Sites
There are a multitude of sensor options available for continuous stream monitoring. As these sensors become more advanced and cheaper, selecting the correct one for your monitoring can be difficult. Here are the sensors that the StreamPULSE project supports.
Water Level -- Onset HOBO HOBO-U20L http://www.onsetcomp.com/files/manual_pdfs/12315-E-MAN-U20.pdf
Solinst 3001 https://www.solinst.com/products/dataloggers-and-telemetry/3001-levelogger-series/operating-instructions/user-guide/3001-user-guide.pdf
Dissolved Oxygen -- Onset HOBO HOBO-U26 http://www.onsetcomp.com/files/manual_pdfs/15603-B-MAN-U26x.pdf
Campbell Scientific CS511 https://www.campbellsci.com/cs511-l
Specific Conductance -- Onset HOBO HOBO-U24 http://www.onsetcomp.com/files/manual_pdfs/15070-C-MAN-U24x.pdf
Campbell Scientific CS547 https://www.campbellsci.com/cs547a-l
pH -- Campbell Scientific CS526 https://www.campbellsci.com/cs526
Turbidity -- Turner Cyclops-7 http://www.turnerdesigns.com/t2/doc/manuals/998-2100.pdf
fDOM -- Turner Cyclops-7 http://www.turnerdesigns.com/t2/doc/manuals/998-2100.pdf
Nitrate -- Satlantic SUNA http://www.seabird.com/sites/default/files/documents/SUNAe.pdf
Light -- Onset HOBO HOBO-U002 http://www.onsetcomp.com/files/manual_pdfs/9556-I-MAN-UA-002.pdf
Air Pressure -- Onset HOBO HOBO-U20L http://www.onsetcomp.com/files/manual_pdfs/12315-E-MAN-U20.pdf
Precipitation -- Onset HOBO HOBO-RG3M http://www.onsetcomp.com/files/manual_pdfs/10241-L%20MAN-RG3%20and%20RG3-M.pdf
Data Logger -- Campbell Scientific CR1000 https://s.campbellsci.com/documents/br/manuals/cr1000.pdf
Installing Sensors for Continuous Monitoring
From USGS
Link to Photos of Current StreamPULSE sites ***This is linked to my personal Google Drive***
Site Characteristics
- Potential for water-quality measurements at the site to be representative of the location being monitored
Degree of cross-section variation and vertical stratification
Channel configuration that may pose unique constraints
Range of stream stage
Water velocity
Presence of turbulence that will affect water-quality measurements
Conditions that may enhance rate of fouling, such as excessive fine sediments, algae, and invertebrates
Range of values for water-quality field paramters
Need for protection from high-water debris damage and vandalism
Monitor Installation
- Type of state or local permits before installation can begin
Safety hazards relevant to monitor construction and installation
Optimal type and design of installation
Consideration of unique difficulties
Costs of installation
Logistics
- Accessibility of site
Safe and adequate space to perform maintenance
Presence of conditions that increase the frequency of servicing
Proximity to location for making cross-section measurements
Accessibility and safety of site during extreme events
Rantz and others, 1982 Hydraulic conditions of the ideal gage site
- General course of the stream is straight for about 300 feet upstream and downstream of gage site
Total flow is confined to one channel at all stages, and no flow bypasses the site as subsurface flow
Streambed is not subject to scour and fill, and is free of aquatic growth
Banks are permanent, high enough to contain flood waters, and free of brush
Unchanging natural controls are present in the form of a bedrock outcrop or other stable rifle for low flow and a channel constriction for high flow, or a falls or cascade that is no submerged at all stages
Pool present upstream of the control at extremely low stages to ensure a recording stage at extremely low flow, and to avoid high velocities at the streamward end of gaging site intakes during periods of high flow
Gaging site is far enough upstream from a confluence with another stream or from tidal effect to avoid any variable influence on stage at the gage site from the other stream or tide
Satisfactory reach for measuring discharge at all stages is available within reasonable proximity of the gage site
Site is readily accessible for ease of installation and operation of the gaging station
Site is not susceptible to man made disturbances, nearby tributaries, or point-source discharges
Placement of Sensors in the Aquatic Environment
Placement of a water-quality monitoring sensor is dependent on the purpose of monitoring and the data-quality objectives. The data-quality objectives for the measurement of loads or flux in a stream or river generally require placement of a water-quality monitoring sensor at a location that is representative of conditions in the stream cross section. Some environments, such as lakes, estuaries, or poorly mixed streams, preclude sensor placement at one representative point, and alternative monitoring strategies must be considered. For example, multiple sensors can be located in vertically or horizontally stratified aquatic environments. Another option is the use of a flow-through monitor configuration (see Monitor Configurations and Sensors) with intakes located at multiple depths or horizontal locations. Alternatively, if poor mixing occurs only during particular seasons or flow conditions, sensors can be placed at the optimal location, and the rating of the accuracy of the record (see Publication Criteria) can be downgraded during periods of poor mixing. In all cases, it is necessary to characterize the vertical and horizontal mixing at the monitor site with measurement surveys of vertical and horizontal cross-section variability (see Stream Cross-Section Surveys).
Stream Cross-Section Surveys
The data objectives for most continuous water-quality monitoring stream sites require that the sensors be placed at locations that are representative of average measurements in the stream cross sections. Before a monitoring site is installed, surveys of the cross-section variability of the field measurement(s) to be monitored are required to determine the most representative measurement point in the stream cross section and to determine if a cross-section correction is necessary. Data from cross-section surveys can be used to correct single-point measurements in poorly mixed streams to better represent the cross-section average. By choosing a monitoring site with well-mixed streamflow, however, cross-section corrections may not be needed.
A sufficient number of cross-section surveys representing different flow conditions is required to determine if discharge or seasonal changes significantly affect mixing in the cross section for the field measurement(s) to be monitored. A minimum of two cross-section surveys per year is required to verify or revise results from previous surveys. Temporal changes in cross-section variability in some streams may require more frequent surveys. Documentation of vertical mixing is required at least once per year at a minimum of two depths for all cross sections.
The most efficient means of obtaining cross-section surveys is with a calibrated multisensor sonde that can measure the same field parameters that are being recorded by the monitor. At locations with high stream velocities, it may be necessary to attach the sonde to a sounding weight. Discrete samples should not be composited for measurement of cross-section averages. The standard USGS procedure for selecting measurement points for making a cross-section survey and calculating a cross-section mean value is to divide the stream cross section into increments using either the discharge- or area-weighted method (Webb and others, 1999). Generally, measurements are needed in the centroid of a minimum of four equal-discharge increments to provide a discharge-weighted mean. These multiple measurements also establish the horizontal cross-section variability of a measured field parameter. Alternatively, mid depth measurements can be made at the midpoint of equal-width increments to determine an area-weighted mean value. Generally, a minimum of 10 and a maximum of 20 equal-width increments across a large stream or river are needed to establish the area-weighted mean value and horizontal cross-sectional variability of a field parameter. Examples of both area- and discharge-weighted cross-section average calculations are given in Wilde and Radtke (2005).
Multiple vertical measurements may be needed depending on the degree of vertical mixing. If physical or chemical vertical stratification is observed, the number of vertical measurements may need to be increased from middepth to two measurements (0.2 and 0.8 of the depth) or more. Alternatively, measurements can be made at points relative to changes in field parameters, such as temperature or salinity gradients, if these are documented. If the vertical stratification is sharply defined, the measurements across the transition zone must be more closely spaced to represent the position and degree of stratification adequately.
Sensor Calibration
PLEASE USE CALIBRATION IN SENSOR MANUALS LINKED ABOVE
Listed below are USGS guidelines for all sensors
The three major uses for a field meter during servicing of a continuous water-quality monitor are (1) as a general check of reasonableness of monitor readings, (2) as an independent check of environmental changes during the service interval, and (3) to make cross-section surveys or vertical profiles in order to verify the representativeness of the location of the sonde in the aquatic environment. The field meter should not be used directly to calibrate the water-quality monitor nor in the computation of monitor records. With the exception of temperature, it is important not to give too much credence to meter-to-meter comparisons. Independent field measurements must be made before, during, and after servicing the monitor to document environmental changes during the service interval. Measurements are made at the monitoring site by locating calibrated field instruments as close to the sensor as possible and at 5-minute intervals, or more frequently if necessary.
Before site visits, all support field meters should be checked for operation and accuracy. Minimum calibration frequency for each type of meter is detailed in Anderson (2004) and Wilde and Radtke (2005). All calibrations must be recorded in instrument logbooks, along with all calibrations, measurements, results from USGS National Field Quality Assurance (NFQA) Program samples, and information about sensor replacements, instrument upgrades, or other periodic calibrations.
Temperature
Proper certification and documentation for liquid-in-glass thermometers and thermistor thermometers are detailed in Radtke and others (2004). Thermometers must be calibrated or checked against a calibration thermometer, which is either certified by the National Institute of Standards and Technology (NIST) or certified by the manufacturer as NIST traceable (Radtke and others, 2004). Liquid-in-glass thermometers and thermistors must be accurate within + 0.2 °C. For both thermistors and liquid-in-glass thermometers, an annual five-point calibration is required over the temperature range of 0 to 40 °C using a temperature-controlled water bath and an NIST-certified or NIST-traceable thermometer to ensure accurate temperature measurement. In addition, two-point calibration checks over the maximum and minimum expected annual temperature range must be made three or more times per year for thermistors and two or more times per year for liquid-in-glass thermometers. Calibrated thermometers and thermistors must be marked with the date of calibration.
Specific Conductance
Proper calibration and documentation for specific conductance meters are detailed in Radtke and others (2005). Calibration and adjustments for multiparameter sensor systems are found in manufacturers’ servicing manuals. Calibration standard solutions of known quality that bracket the expected full range of anticipated values are used to calibrate the specific conductance meter to the appropriate units for particular field conditions. Calibration is performed at the field site with calibration standard solutions that have been allowed to equilibrate to the temperature of the water being monitored. The USGS reports specific conductance compensated to 25 °C. Most meters have automatic temperature compensation circuits that permit readings in microsiemens per centimeter at 25 °C, but this should be verified by checking the manufacturer’s instruction manual. The accuracy of the meter should be within 5 percent for specific conductance values less than or equal to 100 μS/cm, or within 3 percent for specific conductance values greater than 100 μS/cm. Specific conductance standards are available from the USGS National Field Supply Service (NFSS). Calibration standard solutions must be discarded after use as described by Wilde (chapters variously dated).
Dissolved Oxygen
Proper calibration and documentation for DO meters are detailed in Lewis (2005). Calibration and adjustments for multiparameter sensor systems are provided in manufacturers’ servicing manuals. The most commonly used DO sensors measure the partial pressure of DO by the flow of oxygen through a porous membrane and oxygen consumption at a cathode. The calibrated accuracy of DO meters should be within the lesser of 5 percent or + 0.3 mg/L. Meters must be calibrated to 100-percent DO saturation and checked with a zero DO solution to provide an indication of sensor-response linearity. Calibration of a DO meter at 100-percent oxygen saturation is made by adjusting the meter reading for air saturated with water vapor to a value obtained from a DO solubility table (http://water.usgs.gov/software/dotables.html; Lewis, 2005) generated from the equations of Weiss (1970). The DO solubility is based on the water temperature, the uncorrected barometric pressure, and salinity. A reliable pocket altimeter can be used to measure uncorrected (true) barometric pressure to the nearest 1 millimeter (mm) of mercury; a specific conductance meter can be used to measure salinity. The accuracy of a DO meter at 0.0 mg/L is verified by measuring the DO of a fresh solution of sodium sulfite, prepared as described by Lewis (2005). The zero-DO measurement also serves to ensure the integrity of the electrolyte solution, the membrane, and the retaining ring. Calibration and operation procedures differ among instrument types and makes, and the manufacturer’s instructions must be followed closely.
pH
A detailed description of the 10-step calibration process for pH meters, including a wide range of available equipment, is provided by Radtke and others (2003). Calibration and adjustments for multiparameter sensor systems are available in manufacturers’ servicing manuals. Accuracy of field pH meters should be at least + 0.1 pH unit. Two standard buffer solutions bracketing the expected range of environmental values are used to calibrate a pH electrode, and a third is used as a check for calibration range and linearity of electrode response. The pH-7 buffer is used to establish the null point, and a pH-4 or pH-10 buffer is used to establish the slope of the calibration line at the temperature of the solution. The slope of a pH electrode is temperature sensitive, but the pH slope for modern sensors usually is adjusted to the observed temperatures through automatic temperature compensation by use of the theoretical Nernst equation (Radtke and others, 2003). It is important that the temperatures of the buffers be as close as possible to the samples being measured. Immersing the pH buffer bottles in the aquatic environment for about 15 minutes allows the buffer temperature to equilibrate to the aquatic environment. Standard buffers of pH 4, 7, and 10 are readily available from the NFSS. Proper calibration of pH sensors does not ensure accurate pH measurements for low specific conductance waters. Consult the USGS National Field Manual for the recommended procedure when the specific conductance of the water sample is less than 100 μS/cm (Busenberg and Plummer, 1987; Radtke and others, 2003).
Turbidity
Proper calibration and documentation for turbidity meters are described by Anderson (2004). The three types of turbidity calibrants are (1) reference turbidity solutions, (2) calibration turbidity solutions, and (3) calibration verification solutions and solids. Reference turbidity solution is a calibrant that is synthesized reproducibly from traceable raw materials by a skilled analyst. The reference standard is fresh user-prepared formazin, prepared as described by Anderson (2004) or American Public Health Association (1998). All other calibrants are traced back to this reference solution. Calibration of a turbidity instrument by using reference turbidity solutions should be done only in the laboratory.
Meters are calibrated using calibration turbidity solutions, which must be traceable and equivalent to the reference turbidity calibrants. Acceptable calibration turbidity solutions include commercially prepared formazin, stabilized formazin (such as StablCalTM), and styrene divinylbenzene (SDVB) polymer standards (such as Amco AEPA-1TM Polymer). Calibration turbidity solutions for various ranges are available commercially. Formazin-based calibrants can be diluted by using a dilution formula; however, errors may be introduced during the dilution process, thus reducing the accuracy of the standard solution. Formazin-based calibrants also are temperature dependent, and accurate readings may be difficult to obtain during field conditions. Anderson (2004) suggests that the effect of thermal fluctuations can be minimized by calibrating the instrument at room temperature in an office laboratory using a reference or calibration turbidity solution. Instrument calibration can then be checked at the field site by using a calibration verification calibrant.
Calibration verification calibrants may include, but are not limited to, calibration turbidity solutions; however, calibration verification calibrants that are sealed or solid materials must not be used to adjust instrument readings (Anderson, 2004). Before placing the sensor in a calibration verification calibrant, the sensor must be cleaned, rinsed three times with turbidity-free water, and carefully dried. Turbidity-free water is prepared as described by Anderson (2004).
Sensor Maintenance
- Conduct site inspection
Record monitor readings, time, and monitor conditions
With independent field meter, observe and record readings and time near sensors
Remove sonde from monitoring location
Clean sensors
Return sonde to monitoring location
- Record monitor readings and time
With independent field meter, observe and record readings near the sensors
Remove sonde, rinse thoroughly, and check calibration
Record calibration-check values
Recalibrate if necessary
Return sonde to monitoring location
- Record monitor readings and time
With independent field meter, observe and record readings near the sensors
The standard protocol for servicing instream monitors is described below:
- Obtain a discrete measurement from a clean, calibrated field meter at the sonde location
Remove sonde from the monitoring location being careful to minimize disturbance 3. Connect monitor to field instrument (i.e. computer or hand held device)
If monitor is to be submerged during read-out, ensure the cable is designed to operate under water
Stop unattended monitoring
Upload data
Record any significant fouling observed during monitor removal
Conduct monitor inspection
Record time, readings, and monitor conditions
With an independent field meter, record instream readings and time near the monitor
Clean sensors (see field cleaning of sensors)
Return sonde to the stream
Record monitor readings and time
Using an independent field meter, record instream readings near the monitor
Remove sonde, and check calibration (see field calibration of sensors)
Record calibration-check values
Recalibrate if necessary (see calibration criteria)
Conduct final readings
Record monitor readings and time
Using an independent field meter, observe and record readings near the monitor
Restart unattended sampling with appropriate logging interval, start time, and file name
DWQS recommends a delay start time of 1-2 hours to allow equipment to acclimate following disturbance of the site
Check monitor’s battery levels, change if necessary
Return sonde to monitoring location and inspect anchoring equipment and shroud for deterioration and damage.
Maintenance functions during field visits
- Calibration of field meters
Inspection of site for signs of physical disruption
Inspection and cleaning of sensors for fouling, corrosion, or damage
Inspection and cleaning of deployment tube
Battery check
Time check
Routine sensor cleaning and servicing
Calibration check and recalibration if necessary
Downloading of data
Installation Equipment List
- Laptop w/ software installed
Sensors
Notebook
Digital camera
Clipboard
Watch
Pencils, pens, sharpies
Maps
Batteries
Gloves
Hand sanitizer
5 gallon buckets
Cable Ties (UV resistant/Black Strong)
8 or 10 gauge flexible wire
Spiral wrap for cables
Wire cutters
Soldering iron
Hammers (small and sledge)
Tape (electrical, steel, duct, engineers)
Chain
12ft 4X4 fence post
Flex conduit
Post hole digger, shovels
4in deck screws
Washers for screws
Concrete screws/ bolts
Battery powered DeWalt drill and saw
Drill bits for wood, steel, and rock
Generator and extension cords
Rags
Zip ties
Hose Clamps (all sizes)
Screwdrivers, Wrenches, Knives
Strongbox for datalogger housing
Underwater cement epoxy
Plumber's Puddy
Gutter sealer, Silicone, Liquid Nails
U-bolts w/ bar
8ft T-post
Rebar
4-6in PVC w/ pre-drilled holes (Sensor housing)
Sample bottles and filters
Quickrete for post hole
GPS
Degree of cross-section variation and vertical stratification
Channel configuration that may pose unique constraints
Range of stream stage
Water velocity
Presence of turbulence that will affect water-quality measurements
Conditions that may enhance rate of fouling, such as excessive fine sediments, algae, and invertebrates
Range of values for water-quality field paramters
Need for protection from high-water debris damage and vandalism
Safety hazards relevant to monitor construction and installation
Optimal type and design of installation
Consideration of unique difficulties
Costs of installation
Safe and adequate space to perform maintenance
Presence of conditions that increase the frequency of servicing
Proximity to location for making cross-section measurements
Accessibility and safety of site during extreme events
Total flow is confined to one channel at all stages, and no flow bypasses the site as subsurface flow
Streambed is not subject to scour and fill, and is free of aquatic growth
Banks are permanent, high enough to contain flood waters, and free of brush
Unchanging natural controls are present in the form of a bedrock outcrop or other stable rifle for low flow and a channel constriction for high flow, or a falls or cascade that is no submerged at all stages
Pool present upstream of the control at extremely low stages to ensure a recording stage at extremely low flow, and to avoid high velocities at the streamward end of gaging site intakes during periods of high flow
Gaging site is far enough upstream from a confluence with another stream or from tidal effect to avoid any variable influence on stage at the gage site from the other stream or tide
Satisfactory reach for measuring discharge at all stages is available within reasonable proximity of the gage site
Site is readily accessible for ease of installation and operation of the gaging station
Site is not susceptible to man made disturbances, nearby tributaries, or point-source discharges
Record monitor readings, time, and monitor conditions
With independent field meter, observe and record readings and time near sensors
Remove sonde from monitoring location
Clean sensors
Return sonde to monitoring location
- Record monitor readings and time
With independent field meter, observe and record readings near the sensors
Remove sonde, rinse thoroughly, and check calibration
Record calibration-check values
Recalibrate if necessary
Return sonde to monitoring location
- Record monitor readings and time
With independent field meter, observe and record readings near the sensors
Remove sonde from the monitoring location being careful to minimize disturbance 3. Connect monitor to field instrument (i.e. computer or hand held device)
If monitor is to be submerged during read-out, ensure the cable is designed to operate under water
Stop unattended monitoring
Upload data
Record any significant fouling observed during monitor removal
Conduct monitor inspection
Record time, readings, and monitor conditions
With an independent field meter, record instream readings and time near the monitor
Clean sensors (see field cleaning of sensors)
Return sonde to the stream
Record monitor readings and time
Using an independent field meter, record instream readings near the monitor
Remove sonde, and check calibration (see field calibration of sensors)
Record calibration-check values
Recalibrate if necessary (see calibration criteria)
Conduct final readings
Record monitor readings and time
Using an independent field meter, observe and record readings near the monitor
Restart unattended sampling with appropriate logging interval, start time, and file name
DWQS recommends a delay start time of 1-2 hours to allow equipment to acclimate following disturbance of the site
Check monitor’s battery levels, change if necessary
Return sonde to monitoring location and inspect anchoring equipment and shroud for deterioration and damage.
Inspection of site for signs of physical disruption
Inspection and cleaning of sensors for fouling, corrosion, or damage
Inspection and cleaning of deployment tube
Battery check
Time check
Routine sensor cleaning and servicing
Calibration check and recalibration if necessary
Downloading of data
Sensors
Notebook
Digital camera
Clipboard
Watch
Pencils, pens, sharpies
Maps
Batteries
Gloves
Hand sanitizer
5 gallon buckets
Cable Ties (UV resistant/Black Strong)
8 or 10 gauge flexible wire
Spiral wrap for cables
Wire cutters
Soldering iron
Hammers (small and sledge)
Tape (electrical, steel, duct, engineers)
Chain
12ft 4X4 fence post
Flex conduit
Post hole digger, shovels
4in deck screws
Washers for screws
Concrete screws/ bolts
Battery powered DeWalt drill and saw
Drill bits for wood, steel, and rock
Generator and extension cords
Rags
Zip ties
Hose Clamps (all sizes)
Screwdrivers, Wrenches, Knives
Strongbox for datalogger housing
Underwater cement epoxy
Plumber's Puddy
Gutter sealer, Silicone, Liquid Nails
U-bolts w/ bar
8ft T-post
Rebar
4-6in PVC w/ pre-drilled holes (Sensor housing)
Sample bottles and filters
Quickrete for post hole
GPS
