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