Water Testing: Appropriate Water Use with Changing Conductivity Levels

Conductivity is a measure of the Total Dissolved Solids in water. Part of these solids is made up of Total Soluble Salts and this is used as a measure of salinity. A particular level or change in salinity indicates what plants and animals can live in the water.

Conductivity is measured by passing an electric current between two metal plates (electrodes) placed in a water sample. If there are high levels of dissolved salts in the sample, the current and, therefore, the conductivity are greater.

Conductivity is measured in micro siemens per centimetre (µs/cm). The natural conductivity of fresh water varies from 30 to 2000 us/cm.

Value µS/cm Water Use
0-800 Good drinking water for humans and livestock. Good irrigation water.

800-2500 Adequate drinking water for humans and livestock. When irrigating choose salt tolerant plants, consider soil type and good drainage.

2500-10000 Not recommended as drinking water for humans. Pigs and poultry can't tolerate water over 6000. Not suitable for irrigation.


10000+ Used to flush toilets. Beef cattle can tolerate water up to 17000 and dry, adult sheep up to 23000.

Conductivity varies naturally with the depth of the water. Variations also occur because of geology, ground water seepage, industrial and agricultural effluent, storm water run-off, land clearing and sewage effluent.

Saline soils and water (shown by high conductivity readings) develop when deep-rooted plants, such as trees, are removed and through poor irrigation practices. Shallow roots, from crops such as wheat, means more rains gets into more deeply into the soil dissolving salts stored there. The water table gets closer to the soil surface bringing with it large amounts of salt. When this water evaporates it leaves the salt behind.

The salt kills plants that can't tolerate it (including crops). Rain washes this salt into rivers, dams and lakes making it less useable for humans, livestock and irrigation.

Readings (for valleys) range between excellent < 80 to poor ³ 750 µS/cm.

Next > pH


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