Hydrology Field Methods - FORS 4130L/6130L

Hydrolab Operation

1. The Hydrolab is a multiparameter probe with the following sensors:

   • Water Depth (m or ft)
   • Temperature (°C or °F)
   • Dissolved Oxygen (mg/L or %saturation)
   • Proton Concentration (pH)
   • Specific Conductance (µS/cm)
   • Turbidity (NTU)

2. Check out the Hydrolab website at www.hydrolab.com

3. There are two ways you can use multiparameter probes:

   • Take manual field measurements and bring the probe back with you.
   • Leave the probe in the field and retrieve the probe and data later.

4. The probe must be calibrated before and after use:

   • Some parameters are stable => temperature, depth
   • Others are very unstable => DO, pH, EC

5. Dissolved Oxygen (DO) calibration:

   • DO saturation changes with temperature and pressure
   • Colder water can hold more oxygen
   • Lower pressure reduces the oxygen concentration
   • Check the air pressure using the local weather station at http://weather.noaa.gov/weather/current/KAHN.html
   • Use the measured water temperature
   • The sensor membrane and solution require replacement on a regular basis

6. Proton Concentration (pH) calibration:

   • We use one or more buffer solutions with known pH
   • Check expiration date of solution
   • Avoid reuse of calibration solution
   • Use a calibration solution that is similar to the system you will measure
   • Reference probe fluid requires replacement on a regular basis

7. Specific Conductance (EC) calibration

   • We use one or two solutions with known EC
   • Check expiration date of solution
   • Avoid reuse of calibration solution
   • Use a calibration solution that is similar to the system you will measure
   • EC probe requires occasional cleaning