Wilson Inlet 5
 |
 |
 |
Water Quality in Wilson Inlet from 1995 to 2002
Comparison to historical data
Given the scale of interannual variability within the water quality parameters measured in the Inlet over the 1995- 2002 period it is difficult to determine any consistent trend, either up or down, over this period. In order to try and detect trends over a longer time frame than the seven years of 1995-2002 data, the current data set was compared to data collected in previous sampling programs. Because of the differences in methods, frequency of sampling, sampling sites and the availability of summary statistics only for some of the programs, the comparison between them and the 1995-2002 program is coarse.
Figures 40 to 45: Comparison of the present data set to historical data collected in Wilson Inlet. Data are presented on a logarithmic
scale. The solid columns represent the average concentration (combined surface and bottom) of each parameter in the data set of
interest and the bars represents the maximum concentrations. Red columns are for the period September to May, blue are for the
period June to August. The data analysed from each project are from basin sites (ie excludes river and ocean mouth sites). The
treatment of the data in this way was an attempt to achieve comparability between data sets and reflects the limited information that
was available for some of those data sets.
Comparison to other inlets
A comparison of the Wilson Inlet water quality data with
other south western Australian estuaries has been made so
as to gauge its relative condition compared to those other
estuaries. The data presented below are medians of all of
the data points for each estuary in the 1995-2001 period,
except for the pre Dawesville Channel Peel-Harvey data
which is for the period 1980 to 1993.
As with the above analysis, the limited number of samples for some estuaries makes the analysis fairly coarse, though instructive nonetheless.
In summary, water quality in Wilson Inlet is on average significantly better than the Peel-Harvey prior to the Dawesville Channel (and for the most part is still better than the Peel-Harvey post Dawesville Channel) and significantly better than in the adjacent Torbay and Parry systems, the Vasse-Wonnerup at Busselton, and the Hamersley, Gordon and Beaufort Inlets to the east. The Inlet's water quality is also better than the Moore River at Guilderton, the Swan River at Perth, the nearby Irwin and Taylors Inlets and the Wellstead Inlet at Bremer Bay. Wilson Inlet's water quality is comparable to the Hardy Inlet at Augusta and Leschenault Inlet at Bunbury, and on some parameters to the nearby Walpole-Nornalup Inlet and Oyster Harbour. The only Inlet that has substantially better water quality than Wilson Inlet is the near pristine Broke Inlet.
Figures 46 to 48: Comparisons of Wilson Inlet chlorophyll a (mg/L), total nitrogen (mg/L) and total phosphorus (mg/L) data to other Inlets in south west WA. Medians of all data.
