September 2020 – Lake Nepean – Algae

Sampling on 21 September recorded 1,293 ASU/mL at the dam wall site. Potential to cause inconvenience to water filtration plant, reducing filter run times. Naturally occurring organism in waterways. Notified Nepean Water Filtration Plant and recommended outlet change to a lower level to avoid algae. Information was provided regarding water quality change at proposed lower outlet level.

January 2021 – Lake Nepean – Algae

Elevated algal ASU in surface water at Lake Nepean.  Potential to cause inconvenience
to water filtration plant, reducing filter run times. Naturally occurring organism in
waterways. Plant notified and additional sampling arranged. Supply depth not impacted (15-20m from surface). ASU reduced in subsequent samples.

March 2021 – Nepean –  E.coli, Cryptosporidium, Turbidity, Colour Manganese

Exceedance of multiple parameters in Nepean raw water – turbidity, true colour, total manganese, total aluminium, alkalinity, MIB, Geosmin, E. coli (870 org/100mL) and
Cryptosporidium (12 oocysts/10L) . Elevated water quality parameters will impact water supply for treatment. Unavoidable turbid intrusion due to extensive heavy rain. Managed as part of ongoing flood incident with daily water quality updates provided to Sydney Water and
NSW Health.