Bendora Reservoir (ACT) – Crytposporidium

1/7/19: Cryptosporidium at a concentration of 0.05 oocysts/L was detected in a composite sample at Bendora intake tower. At the time of sampling water was being abstracted and treated at SWTP. All other water quality parameters were found to be within specification and no Cryptosporidium was detected in the raw water entering the plant or the final supply

Cryptosporidium

“In recent years, Cryptosporidium has come to be regarded as one of the most important waterborne human pathogens in developed countries. Over 30 outbreaks associated with drinking water have beenreported in North America and Britain, with the largest infecting an estimated 403,000 people (Mackenzieet al. 1994). Recent research has led to improved methods for testing water for the presence of humaninfectious species, although such tests remain technically demanding and relatively expensive.

Cryptosporidium is an obligate parasite with a complex life cycle that involves intracellular development in the gut wall, with sexual and asexual reproduction. Thick-walled oocysts, shed in faeces are responsible for transmission. Concentrations of oocysts as high as 14,000 per litre in raw sewage and 5,800 per litre in surface water have been reported (Madore et al. 1987). Oocysts are robust and can survive for weeks to months in fresh water under cold conditions (King and Monis 2007).

There are a number of species of Cryptosporidium, with C. hominis and C. parvum identified as the main causes of disease (cryptosporidiosis) in humans. C. hominis appears to be confined to human hosts, while the C. parvum strains that infect humans also occur in cattle and sheep. C. parvum infection sare particularly common in young animals, and it has been reported that infected calves can excrete up to 10 billion oocysts in one day. Waterborne outbreaks of cryptosporidiosis have been attributed to inadequate or faulty treatment and contamination by human or livestock (particularly cattle) waste.

C. hominis and C. parvum can be distinguished from one another and from other Cryptosporidium species  by a number of genotyping methods. Infectivity tests using cell culture techniques have also been developed. Consumption of contaminated drinking water is only one of several mechanisms by which transmission (faecal-oral) can occur. Recreational waters, including swimming pools, are an important source of cryptosporidiosis and direct contact with a human carrier is also a common route of transmission.Transmission of Cryptosporidium can also occur by contact with infected farm animals, and occasionally through contaminated food.” ADWG 2011

2019/20 Bendora Reservoir (ACT) – Cyanobacteria

28/5/20: High risk cyanobacteria, Microcystis, was detected at notifiable levels in surface water samples at the Bendora reservoir intake tower. At the time of sampling water was being abstracted and treated at SWTP and supplied to ACT and Queanbeyan.

Jan/Feb 2020 Corin Water Supply Reservoir (ACT)

The Orroral Valley fire in January and February 2020 impacted the Namadgi National Park (comprising the southern region of the Cotter catchment including Corin and Bendora water supply reservoirs). 1,951 hectares of Corin catchment and 137 hectares of Bendora
catchment were impacted by high severity fire. A risk assessment was completed to determine the management options in February 2020 and identified that the fire had been of a high intensity and had increased risks to water quality and water treatment needs.

The Cotter catchment bushfire was  followed shortly after by a high intensity rainfall event. Rainfall events following bushfires can have a significant impact on water quality, caused by increased rates of erosion, increased sediments and turbidity, and the introduction of a range of chemicals into the water supply. Rainfall following bushfires can release inorganic nutrients from burnt plant material and lead to an increase in phosphorus and other nutrients
entering waterways which can lead to  future algal blooms.

To minimise impacts to the ACT and regional water supply and in response to the Cotter catchment bushfire and rainfall event, Icon Water implemented the water quality event monitoring program, installed sediment traps to reduce sediment movement in drainage lines and deployed silt curtains on Corin and Bendora reservoirs to contain ash and suspended material.