The fresh water course which supplied the fledgling colony, emptying into Sydney Cove. It was named for three storage tanks which were constructed in the sandstone beside the stream during a drought in 1790. By 1828 the stream had been polluted to such an extent that it could no longer be used as a source of water and was diverted into a sewer, and by the 1870s it had been completely covered. The Tank Stream still flows in a covered storm water drain.