03. Materials & methods measuring water quality


Figure 2. EC/temperature (left) and pH (right) device.

Figure 1. Equipement used to measure the water quality depth profile. Since 2017, I no longer use this analog themometer. Instead I use the digital device shown at figure 2.

  • EC device-1: TDS-3, TDS/TEMP – measures EC in ppm and temperature in degrees Celsius.
  • EC device-2: TDS&EC meter(hold), 0-9999ppm – measures EC in ppm and uS (not reliable) and temperature in degrees Celsius.
  • pH device: pH-ATC, ROHS.
  • EC device-1 was calibrated with a professional EC device. 1 ppm = 2.3331 uS (r2=0.9994, n=5, range: 0-217ppm (0-506uS))


Water quality dragonfly research:

  • The EC, temperature, and pH are measured directly in the water close to the coastline.


Depth profile Liesjärvi:


  • 1.5L plastic bottle anchored with a heavy stone.
  • Thick rope of >20m length that is attached to the bottle and has a knot at every 1m .
  • Thin rope of >20m length with cork attached to one end.
  • Small bucked to collect the water from the bottle.
  • EC device-1 and pH device.
  • Rowing boat


  • Measurments are taken from a rowing boat in the middle of lake Liesjärvi at a position where the water depth is maximum (i.e. 18-19 m).
  • The bottle is closed with the cork and put in the water.
  • At a certain depth (based on knot in rope), the cork is pulled out of the bottle.
  • When the bottle is filled up with water, it is brought to the surface and emptied in the bucket.
  • Immediately thereafter, the measurements (pH, EC, temperature) are taken.
  • Water samples are collected at every 1 m water depth until the bottom of the lake is reached.