Lake Alexandrina (Point Sturt)
Map: Groundwater monitoring locations in Point Sturt
What is acidity?
Acidity is a measure of the acid (hydrogen ions) and dissolved metal ions (e.g. iron and aluminium) present in water bodies. Acidity is expressed as the volume of calcium carbonate (mg/L of CaCO3) required to neutralise any acid. Acidity build up occurs when the alkalinity or buffering capacity has been consumed.
Acidity at Point Sturt
Acidity was recorded in high levels at one site, PS 2S, at Point Sturt during the drought. Acidity has persisted at this site since the water level return. Acidity is also present at two other sites at Point Sturt, although this is at low levels. Monitoring of acidity at these sites will continue.
What is alkalinity?
Alkalinity is a measure of the buffering capacity of water, or the capacity of the water to neutralise acids and resist pH change. It is expressed in milligrams per litre as calcium carbonate (mg/L as CaCO3) and is present in groundwater predominantly due to the weathering of carbonate minerals in the soils.
Alkalinity at Point Sturt
Due to the low pH and high acidity present at site PS 2S throughout the drought and after inundation, there has been no recorded alkalinity at this site. This site will continue to be monitored for any signs of alkalinity improvement. The other sites at Point Sturt were not acidic, and has alkalinity is within normal variation.
What is pH?
pH is an indicator of acidity or alkalinity. pH is a logarithmic scale and an increase or decrease of one pH unit is a 10 fold change. Neutral water has a pH of 7, acidic solutions have values between 0-6 and alkaline solutions have values between 8-14.
pH levels at Point Sturt
There was one low pH groundwater site at Point Sturt during the drought. The low pH is a result of acidity produced as a result of the exposure of acid sulfate soils. Since this sites has been inundated, the pH has increased slightly, although still remains below desirable levels (pH > 6.5).
What is salinity?
Salinity is a measure of the amount of dissolved salts in the water. Saline water conducts electricity more readily than freshwater, so electrical conductivity (EC), measured in micro siemens per centimeters (uS/cm) is routinely used to measure salinity.
Salinity at Point Sturt
Salinity in the groundwater is naturally much higher than the overlying surface water due to accumulated dissolved salts from weathered soil materials. At Point Sturt, fresher surface water conditions since the inundation of these sites has allowed groundwater salinity decrease slightly.