The water quality in Western Port is generally good. The State environment protection policy (SEPP) objectives for Western Port have been achieved, overall, on 88% of samples in recent times, as outlined in the table below.
However, turbidity levels are often high, particularly in the northern and western parts of Western Port. High turbidity, caused by suspended sediments, reduces light penetration and hampers the ability of seagrass and mangrove communities to flourish.
The monitoring indicates that water quality degrades as it cycles clockwise around Western Port. The Hastings and Barillier monitoring sites consistently attain more SEPP objectives than the Corinella site for all parameters. The Corinella site also failed to attain SEPP objectives for metals on occasion when the other sites attained them.
Historically monitoring for Western Port has been inconsistent and infrequent. Some parameters were only sampled once a year. Because data can be easily skewed when few samples are taken over a twelve month period, confidence in the results for years with less data, such as 2002, 2006 and 2007, is relatively low. Confidence is significantly greater for results where monitoring data has been much more abundant, frequent and consistent such as 2001, 2003, 2008, 2009 and particularly 2010. An increased program of monitoring was undertaken in 2010 resulting in a greater quantity of data for each parameter.
Summary of the attainment of SEPP objectives in Western Port (2011/12)
This assessment of the condition of marine waters is used as the basis for setting targets for the future (Targets). The values marine waters support has been mapped (Map). The condition of marine waters has been assessed (Method & Condition). Lead organisations are committed to addressing the pressures to target attainment. Arrangements are in place to monitor and report on progress.