The Central and East Basins of Lake Burley Griffin are closed for swimming because of high levels of bacteria.
The Captain Cook Memorial Jet has been turned off until further notice.
National Capital Authority took samples from around the lake on November 2 and found the East Basin sample had Enterococci levels of 1460 MPN/100mL, which is more than seven times the acceptable level.
The Captain Cook Memorial sample measured 460 MPN/100mL, which is more than twice the acceptable level.
Swimming in the contaminated water could lead to illness, including gastroenteritis, respiratory illness, ear infections, and skin and eye problems.
Other waterways around Canberra are also currently closed for swimming due to high levels of bacteria.
On the Murrumbidgee River, Uriarra East and West, Swamp Creek Beach, Kambah Pool, Point Hut Crossing and Tharwa Bridge are closed.
At Lake Ginninderra, Bimbi Beach is closed and on Lake Tuggeranong Nguru Beach is closed.
The water ski boat ramp and canoe area on the Molonglo River are also closed due to bacteria.
The ACT government City Services website warned bacteria levels were often elevated after significant rainfall.
The ACT government and National Capital Authority conduct weekly water quality testing during the recreational season.
