Lakes and reservoirs are essential for water supply for humans and agriculture, and have an important role in flow regulation, biodiversity, and streamflow below dams. Australia has been subject in recent decades to severe drought which has heightened the importance of reservoirs for human populations and highlighted the need for careful management of water levels to maintain continuity of supply. Climate change is likely to exacerbate water shortages, with extended periods of drought, interspersed with more discrete and intense rainfall, leading to challenges for storing water in reservoirs and potentially affecting the quality of water.

In this project, Griffith University researchers examined the water quality risks from low and variable water levels in dams and reservoirs in Eastern Australia.

In 2006, strict restrictions on using tap water for gardening or car-washing were imposed in Melbourne but relaxed in 2010-2011 as rainfall replenished depleted reservoirs. During this five-year period residents collected their own greywater from washing machines and laundry, showers, baths, and kitchens. The problem with this is that people with diarrhoea and gastrointestinal illness might soil bed linen or clothes, or have an accident in the bathroom, and inadvertently transfer pathogens into the greywater. The worst-case scenario is that greywater containing infectious pathogens is used to water lettuce in a way that transmits infection to those eating unwashed leaves. The Environmental Protection Agency of Victoria (EPAV) published Guidelines (2008) designed to minimise harm to health or the environment. This research examined 1621 households and concluded that although half knew the guidelines existed, they were not following the advice, but nevertheless, although this study was limited, there appeared to be no significant increase in gastrointestinal illness. This research recommended that future housing design incorporate integrated water management strategies to enable safe greywater collection.

There are concerns that recycled wastewater used for watering gardens or washing cars might be accidently ingested. The problem with this is that water for irrigation is not recycled to the same high (and expensive) standard as potable drinking water and might contain pathogens that cause diarrhoea and illness. Recycled water providers must quantify the risk that irrigation water might pose to public health, even though it is not supposed to be drunk. This research worked on the first part of this health risk quantification problem by developing a method to measure the amount of water a person might ingest while, for example, washing a car. Harmless cyanuric acid is commonly added to swimming pools and swimmers often ingest pool water. The amount of cyanuric acid measured in their urine is related to the volume of pool water they ‘drank’. Domestic users of recycled water are more likely to ingest less recycled water than swimmers, so a more sensitive ‘GCMS’ method for measuring very low levels of cyanuric acid was developed. It was shown to work after cyanuric acid was added to water, drunk by three adult volunteers, and then measured in their urine.

Climate change is depleting water resources, while population increases drive demand for additional recreational facilities, particularly in the vicinity of urban centres. It was thought that public access to water catchment land and reservoirs might cause large-scale outbreaks of disease, and that the water-consuming public would have to pay more for the additional water treatment required to keep drinking water free of the organisms that cause infectious disease. Some consider this unfair because it is an added expense that results from recreational access by a minority of the population. This research considered peer-reviewed literature, policy and regulation, hazard and risk assessment procedures, and placed these in the context of interviews, focus group interactions and surveys. It was concluded that although the science of the adverse effects of recreational access on water quality continues to stand up to examination, there is now justification for conducting an advanced risk-benefit analysis which was developed during the study. This uses a ‘multi-attribute utility’ approach that enables assessment of any given situation by incorporating cross-impact matrices. This risk-benefit methodology addresses the significant issues that arise when adjusting or implementing new recreational access priorities.