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  • James Howey

Drought - how does it affect our water quality?

There is no doubt that a drought is devastating. Our agricultural sector has been hit very hard, with farmers in rural NSW and Queensland facing immence difficulties feeding and watering their live stock and sustaining their crops in what has been dubbed "The big dry".

The effects of the big dry also extends to our drinking water supply, as both our surface and ground water sources depend on recharge from rainfall in our catchment areas. Indeed, this morning articles in the news have suggested that the drought could result in Sydney having to introduce drought restrictions (source 1), with concerns of falling dam levels.

There is an obvious link between drought and water scarcity, however there is a less obvious link between drought and issues with drinking water quality. This has been examined in several scientific articles, using water quality results from water sources during periods of low rainfall, and comparing it to periods of good rainfall. Zwolsman and van Vliet (2008) conducted a study and found that during times of low river flows, there is evidence of deteriotion of water quality during droughts, causing higher water temperatures, eutrophication and some heavy metals. Drought conditions for surface waters were linked to algal blooms, with conditions (high temperatures, long resident times and increased nutritient concentrations). Lower flow conditions will likely increase raw water turbidity and pH, due to low flushing and increased resuspension due to shallow water levels. (Mosely, 2014).

Literature suggests links between droughts and climate change, and therefore links between climate change and poor surface water quality (Nosrati, 2011).

Poor water quality for surface water means that as climate change progresses, water utilities will likely face increased challenges due to water quantitiy variations, higher concentrations of nutrients, organic loads and chemicals. Further high temperatures in source water will likely contribute to higher pathogen concetrations in raw water (Depla et al, 2009). This will therefore increase the requirements for effective process optimisation, especially in regard to flocculation, coagulation and filtration operations.


1. Baker, 2018, Could NSW drought lead to Sydney water restrictions?

2. Zwolsman and van Vliet, 2008, Impact of summer droughts on the water quality of the Meuse river, Journal of Hydrology

3. Nosrati, K, 2011, The effects of hydrological drought on water quality, Proceedings of Water Quality: Current Trents and Expected Climate Change Impacts symposium in Melbourne Australia

4. Mosley, L, 2014, Drought impacts on the water quality of freshwater system; review and integration, Earth-science reviews

5. Depla, I, Jung, A.-V., Baures, E, Clement, M., Thomas, O., 2009, Impacts of climate change on surface water quality in relation to drinking water production, Environement International

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