Bore Water Quality, Buckingham Estate
Two samples of bore water were taken on 8 and 11 Feb 2011 from a tap in lot 48. About 100 litres was run from the tap before each sample was taken.
I analysed the samples for electrical conductivity at Geoscience Australia (where I work as a geologist) using a portable conductivity meter. This is a simple test that indicates the saltiness of water.
The results are conductivities of 3.68 and 3.54 deciSiemens per metre (dS/m) respectively. This compares with earlier readings of 2.3 and 3.1 dS/m taken by me about 8 and 4 years ago, indicating that the salinity of the Buckingham aquifer is rising.
According to the Queensland Department of Environment and Resource Management (http://www.derm.qld.gov.au/factsheets/pdf/water/w55.pdf) the water has a very high water salinity rating. This salinity of water is also above the threshold for reduced yield for most fruit and vegetables. Some examples of thresholds (for our soil type) are:
Peach 2.7
Apricot 1.4
Grape 1.9
Apple 1.2
Strawberry 0.9
Zucchini 4.2
Asparagus 3.0
Broccoli 2.8
Cucumber 2.4
Pea 1.8
Tomato 2.0
Potato 1.8
Lettuce 1.5
Beans 1.1
Carrot 1.2The water conductivity of about 3.6 dS/m indicates a total dissolved salt (TDS - this can include Sodium, Calcium, Magnesium, Chloride, Bicarbonate and Sulphate – our water is probably high in Calcium, Magnesium and Bicarbonate) content of a little over 2000 milligrams per litre, ie 2 kg per 1000 litres or kilolitre (one cubic metre of water). The Australian Drinking Water Guidelines (ADWG) states that “based on taste, TDS in drinking water should not exceed 500 mg/L” although “water with a TDS content of up to 1000 mg/L is acceptable to many”. The World Health Organization (WHO) also comments “the palatability of water with a TDS level of less than 600 mg/L is generally considered to be good; drinking-water becomes significantly and increasingly unpalatable at TDS levels greater than about 1000 mg/L”.
Rainwater generally has less than 100 mg/L, and Adelaide water (generally noted for its poor taste and hardness) is generally 250-400 mg/L.
I would not drink our bore water, and I definitely would not put it through my household water system, as it will probably deposit scale in the pipes, and cause corrosion of hot water systems.
The Buckingham aquifer is of the fractured rock type. Typically this type of aquifer has a low water content (usually only a few % by volume) compared to sedimentary aquifers (sands and gravels, such as the Bungendore town supply) which can have water contents up to 35%. Bores in fractured rock aquifers can perform well for stock and domestic supply. However, Buckingham relies on 2 closely spaced bores to supply 50 households.
I consider that we are probably pumping our aquifer at a rate far in excess of natural recharge, and because of this our yields have reduced and the salinity has increased. The current wet conditions do not seem to have filtered through to the aquifer.
I also consider that heavy use of the bore water will lead to a salt build up in the soil, further reducing plant yields and possibly killing sensitive plants. One result of increasing soil salinity is that the soil has to be kept wetter to allow plants to take up their water requirements. This can become a vicious spiral of plants needing wetter soil, more watering, and increased soil salinity.
David Gibson 11/Feb/2011