Post on 30-Dec-2015
transcript
Continuous Water-Quality Field Methods
Micelis Doyle & Joe Rinella
U.S. Geological Survey
503-251-3226 & 503-251-3278
mcdoyle@usgs.gov
jrinella@usgs.gov
Course Overview 4/23/08, Wednesday, 11:30 AM to 12:20 PM
Description of water-quality monitorsDescription of parameters and their useOverview of field trip activities
4/25/08, Friday, 12:45 PM to 16:45 PMField trip to Clackamas River at Oregon City to
calibrate a water-quality monitor
4/28/08, Monday, 11:30 AM to 12:20 PMDebriefing of field work, discussion, and review of
homework
Reading AssignmentGuidelines and Standard procedures for
Continuous Water-Quality Monitors: station Operation, Record Computation, and Data Recording (USGS Techniques and Methods 1-D3)
Read pages 1-22
http://pubs.usgs.gov/tm/2006/tm1D3/
Homework question set is due on 4/28/08
Instructions for driving to Clackamas River at Oregon City
field site on Friday, 4/25/08
• Meet at the site at 1:15 PM
• Bring clipboards and pencils
• See map with driving instructions
• If lost, call 503-730-6706
Water Quality• Water temperature• Dissolved oxygen• pH• Major ions and specific conductance• Alkalinity and acidity• Erosion and sedimentation--suspended sediment and
turbidity• Eutrophication—nutrients (e.g. nitrate, ammonia,
phosphates—not measured in the Clackamas River)• Contaminants
Inorganic chemicals (e.g. trace metals)Organic (e.g. pesticides and industrial chemicals)
• Fecal indicator bacteria• Total dissolved gas• Health of biota (including chlorophyll)
Types of sensors
• Water temperature• Specific conductance• Dissolved oxygen• pH• Turbidity• Chlorophyll—free-floating algae• Total dissolved gas• Chemical species (e.g. nitrate, ammonia,
phosphates)
Conditions that change water temperature
• Solar heating — seasonal/daily
• Thermal loss — air or streambed
• Inflows — Ground water or surface water
• Outflow — less dilution water
Conditions that change specific conductance
(Measure of the capacity of water to conduct an electrical current—function of dissolved ions)
• Dilution (e.g. rain water runoff)
• Evaporation — concentrates chemicals in water
• Inflow/outflow• Chemistry (e.g. weathering of minerals,
runoff from land applications, & point sources)
Conditions that change dissolved oxygen
• Temperature
• Aeration
• Biological activityPhotosynthesis in presence of sunlight 6 CO2 + 6 H2O C6H12O6 (sugar) + 6 O2
(consumes CO2 and produces O2)
• Salinity
• Atmospheric pressure
Conditions that change pH(- Log of the hydrogen ion activity)
• Dissolved gas exchange
• Temperature change
• Weathering of minerals
• Biological activity
Photosynthesis in presence of sunlight6 CO2 + 6 H2O C6H12O6 (sugar) + 6 O2
Respiration (O2 is consumed and CO2 is formed)CO2 + H2O HCO-
3 + H+ CO3-2 + 2 H+
Conditions that change turbidity(measure of light that scatters off suspended particles)
• High flow events — erosion and sedimentation
• Inflows with different turbidity levels
• Stream channel disturbance
• Biological activity — algal production
Advantages of continuous, near real-time, water-quality data
• Quickly identify transmission problems
• Recognize erroneous data due to: Fouling
Calibration drift Other problems
• Quickly recognize sensor or monitor malfunctions
• Can quickly respond to problems and optimize the quality of the data
• Early warning of water-quality problems
Operation of water-quality monitors includes:
• Quality assurance and quality controlAccuracyPrecisionReliability
• Water-quality monitor site operationRoutine cleaning, calibration, and maintenance
• Record storage• Record computations to apply data
corrections• Publication• Archiving
• Arrive at site at 1:15 PM
• Wait for all to arrive so that we can enter plant as a group
• Inspect water-quality monitor vehicle and supplies
• Enter plant to perform site maintenance and calibration check as group; once the group is inside, no one else will be able to enter the facility
Site Visit Activities
Site Visit Activities (continued)
• Explanation and inspection of equipment
• Review initial site checks performed while servicing station
• Download data from data logger
• Note river gage height for stream discharge information
• Note any other station information
Site Maintenance and Calibration
• Compare “Before Cleaning” the water-quality monitor (WQM) readings at the site with field (portable) WQM readings in the river
• Remove and clean WQM at the site
• Return site’s WQM to conduit to obtain “After Cleaning” comparison readings with field WQM
• Remove site’s WQM for calibration check
• Calibrate site’s WQM
• Return site’s WQM to conduit and obtain final comparison readings