Frequently Asked Questions: About water quality
questions about the chemical type of the waters, salinity types, the quality of the groundwater for different uses, causes of salinity and various problems.
- Is the salt in LV groundwater (and soil) from seawater?
No. The bedrock sandstones formations were laid down in freshwater rivers or lakes. More recent higher sealevels have never reached the LV. - Did cutting down the trees make the groundwater salty?
Removing extensive native bushland has played a part in salinity of soils in some areas of the LV, especially towards the edges of the alluvial plains. It may not have been a major contributor to groundwater salinity in the main aquifers, but certainly contributed. - Are some areas more salty than others?
Yes, there are sveral smaller subcatchments that have higher salinity levels. There are also some parts of the main alluvial system along the Lockyer Creek where some obseravtion bores hit very saline water, siting in "pockets" at the bottom of the alluvium. These may be semi-confined depressions in the sandstone. - What does "salty" mean? Is it sodium chloride (NaCl) like seasalt?
"Salty" or saline groundwater really refers to the total amount of dissolved salts. This can include the main cations (+) Na, K, Ca, Mg, and the main anions (-) Cl and HCO3. There can be different proportions of these, and it varies throughout the valley. - Has current landuse caused the salinity problems?
This is a big question. The answer is yes and no. Clearing trees and intensive irrigation have increased salinity in places. However, there are some zones where the groundwater have been naturally more saline. - Is the groundwater in the sandstone bedrock more saline than that in the alluvium?
Yes, often 2-3 times as much, but it also varies. - Is groundwater in the basalt aquifers on the ranges saline?
No, usually this groundwater is very good quality as it directly infiltrates from rainfall. - How do you measure "salinity"?
Good question. This causes a lot of confusion. The easiest way to measure salinity is by a conductivity meter; this measures the passage of electric current between two electrodes. It is therefore called electrical conductivity (EC)and is measured in uS/cm (or mS/cm, divide by 1000). Chemical analyses can be done in the laboratory and gives total ions in solution TDI (total dissolved ions)in mg/L. EC multiplied by 0.68 approximately gives TDI for most waters. [see the publication by McNeil & Cox, 2000]