7.3 QUANTITIES OF BALLAST WATER DISCHARGED INTO VICTORIAN PORTS

Walters estimated that from August 1994 to July 1995, a total of 5,873,200 tonnes of ballast water were discharged into Victorian coastal waters from a total of 3416 vessel visits³⁵⁷ Ballast water discharged and number of vessel visits to each port are shown in Table 10.

TABLE 10

Vessel visits and ballast discharged to Victorian ports August 1994 to July 1995

Port	Number of Vessel Visits	Estimated Ballast Water Received (tonnes)1
Melbourne	2651	1,419,600
Geelong	342	1,080,200
Hastings	258	2,262,100
Portland	165	1,111,300

Source: Walters, S. (1996), Ballast Water, Hull Fouling and Exotic Marine Organism Introductions via Ships - A Victorian Study, Publication 494, Environment Protection Authority (Victoria).

Importantly, the study found that the actual quantities of ballast water discharged into Victorian ports were much less than previously thought. For example, Walters estimated that the Port of Melbourne receives approximately 1.4 million tonnes of ballast water per annum. Estimates using previous methods of calculation were 16 and 26 million tonnes respectively³⁵⁸ Such results have implications for ballast management both in terms of placing the quantities of ballast water to be managed in perspective, as well as providing a basis for a practical and realistic response to ballast management in the State.

The Committee notes, however, that small quantities of ballast discharged does not mean that the degree of risk of organism transfer is also small. Data indicating the quantities of ballast water discharged are particularly useful from a management perspective, but less useful for estimating risk of organism transfer. Viable exotic marine organisms discharged with small quantities of water may be translocated as successfully as those from large quantities of water³⁵⁹