Water pH and electrical conductivity - field measurement

Methods guide · June 14, 2026

These are two readings that almost every water researcher takes by reflex whenever they stand by a river or lake. A student on a practical, a monitoring technician, a volunteer checking their stream

  • all begin the same way: calibrate the meter with a buffer, rinse the electrode, submerge it, wait a brief moment for the number to stabilise. This calm, repeatable act hides a surprising amount of information about the state of the water.

Because pH and electrical conductivity are a sensitive duo. The first speaks of chemical balance and of whether anything worrying is happening in the water; the second - of how much mineral salt the water carries, and it can reveal an invisible inflow of pollution in a second. People who measure them regularly learn to catch departures from their own water’s norm - often the first sign that something is changing. It is a simple, accessible and genuinely useful observation.

What pH says, and what conductivity says

pH is a measure of reaction - acidity or alkalinity - on a 0-14 scale (7 is neutral). Natural waters usually fall in the ~6.5-8.5 range. pH is influenced by, among others, catchment geology (limestone rocks buffer it), photosynthesis (which raises pH during the day) and pollution.

Electrical conductivity measures the water’s ability to conduct electricity, which rises with the amount of dissolved ions (salts). It is a convenient indicator of the water’s mineralisation. It is given in µS/cm and standardised to a temperature of 25°C. A sudden jump in conductivity is a classic signal of an inflow - wastewater, field runoff, salinisation.

How to measure it - step by step

Both measurements are taken with a portable meter (pH meter, conductivity meter) or a multiparameter probe.

  1. Calibration before going out / on site. pH - with buffers (most often 7.0 and 4.0 or 10.0); conductivity - with a standard solution (e.g. KCl). This is a step you must not skip.
  2. Rinse the electrode with distilled water and gently dry it before each measurement.
  3. Submerge the sensor in the water (preferably in the current, not in a backwater) and wait for the reading to stabilise - a dozen to several dozen seconds.
  4. Record the result together with the temperature (both parameters depend on it; better meters compensate for it automatically).
  5. After measuring, store the pH electrode wet (in storage solution, never dry).

What the result means

  • pH outside the ~6.5-8.5 range, or clearly deviating from a given water’s usual value, is worth treating as a signal for observation. Remember the natural daily rhythm - during the day photosynthesis raises pH.
  • Conductivity is best read as a baseline and its deviations: you know your water’s typical value, so a sudden rise (or drop) stands out at once. The number alone, without context, says less than its change over time.

The most common mistakes

  • No calibration - the most common cause of “strange” results. The electrode drifts.
  • A dry or dirty pH electrode - it loses sensitivity; it must be stored wet.
  • Measuring in a backwater - water near the bank can be unrepresentative; measure in the flow.
  • Skipping the temperature - without it, comparison is hard, especially for conductivity.

How often

These measurements are practically made for a regular series - on every field visit, at a fixed spot and at a similar time. Only a sequence of readings reveals the trend and lets you tell natural variability from a real signal.

Sources and further reading

The methodologies are described in standards (e.g. ISO 10523 for pH and EN 27888 / ISO 7888 for conductivity) and in GIOŚ materials on the monitoring and classification of surface waters.

How to make it easier

pH and conductivity mean the most as a series and in the context of a given place - which is exactly the easiest thing to lose when readings end up on loose notes or in several separate spreadsheets.

LimnoLog keeps an eye on this for you:

  • recording right on your phone by the water - also offline (sync once back in range);
  • every reading goes to a station and a session, so “the same place, the same time” holds on its own;
  • a chart emerges from the series - the baseline and sudden conductivity deviations are visible instantly;
  • you can share the results via a public link or export them for further analysis.

And since LimnoLog is not limited to two indicators - alongside pH and conductivity you record oxygen, temperature or anything else you happen to be tracking. One set of data instead of scattered notes.

Early users get free access for now and keep their features for good. If you run your own measurements - take a look and try it.

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