It's important for people to understand what the environment of the Vasse and Wonnerup estuaries and of the Lower Vasse River were like
prior to European settlement and how we've changed their environmental character in
the years that followed.
The Vasse and Wonnerup estuaries were fresh
in winter and saline to brackish in summer. The Capel River flowed into
the eastern end of the Wonnerup estuary, with the Ludlow also
contributing its water to the system. Today, the Capel River flows
direct to the sea at Peppermint Grove Beach, so the total amount of
freshwater entering this estuary is probably less than 25% of what it
was.
The Vasse estuary received water from the Abba, Sabina, Vasse
and New Rivers, with water from the latter two watercourses now mostly
diverted to flow direct into the sea. Overall, it's likely that less
than 50% of the original winter water flow is now entering this estuary.
The Lower Vasse River was, according to Pioneer of the Year award
recipient Les Peaker nothing more than a winter-flowing creek that
meandered through dense tea-tree thickets. It contained small permanent
pools along its course in which fish and marron could always be found.
When the Butter Factory floodgate was put in, the check boards turned
this meandering creek into a large permanent pool which, because of the
very low gradient in the river bed, extended for 2 or more kilometres
upstream. It thus formed a very artificial but attractive entrance into
Busselton.
Water quality problems in all these waterbodies are
ultimately caused by excess nutrients. While fertiliser run-off from
farms was the largest and initial source of these nutrients (phosphorous
and nitrogen), urban development around Busselton has added extra
nutrients via septic tanks polluting the groundwater and garden
fertilisers washing off and also adding to the groundwater.
As a
result, we today have 3 legacy issues which have to be dealt with.
First, excess nutrients are still coming from farming land, although the
amount is reducing as farmers improve their land management practices
and as genuine farmers are being replaced by hobby farmers. Second,
nutrients from urban areas are also reducing thanks to better fertiliser
management by the City and by septic tanks being replaced by deep
sewerage. Third, in the bed of the Lower Vasse River and in the Wonnerup
Inlet, there is a thick layer of black, organic- and nutrient-rich
sludge that has accumulated from when the floodgates were first
installed. While the then Shire under Beryle Morgan dredged some of this
sludge out of the Lower Vasse River in the 1980s, most of the
pre-dredging sludge remains and it continues to accumulate.
What to
do? In the Lower Vasse River, there is absolutely no alternatives but to
remove the sludge and to work with farmers in the catchment of the
Vasse River to reduce their nutrient losses. Cost: many millions of
dollars and it will take another 10 or more years for this to happen. In
the meantime, there are some cosmetic actions that can be taken -
fountains that aerate the river water and vegetated floating islands -
see www.fiatechnology.com.au (warning: I'm a director of this company) - but they will only ever treat the symptoms, they won't cure the illness.
In the estuaries proper, a return to hydrological conditions similar to
those that prevailed prior to the installation of the floodgates is
critical, together with removal of the sludge in the bed of the Wonnerup
Inlet. Allowing more 'fresh' seawater into the two estuaries over the
summer and autumn months will improve water quality, allow fish to move
to parts of the estuary system where they won't die of low oxygen levels
or bacterial/algal poisoning, while also providing food habitat for the
30,000+ waterbirds that use the estuaries over the summer. Cost of
better floodgate management: a few 1000 dollars per year. Cost of
dredging: a million or more dollars.
The picture is more
complicated than this, of course, but state govt funding of an
organisation such as GeoCatch which has almost 20 years' experience in
land and water management is critical. Sadly, the announcement by water
minister Mia Davies last October was a non-event, as the money promised
to various bodies was far too small to make any real difference. The
minister's commitment to a committee to report on what actions are
needed next, while commendable in some ways, can also be seen as a way
to defer any serious funding commitments until after it reports in about
a year's time, coincidentally just before the next state election.
You'll have to excuse my cynicism but GeoCatch has studied what needs to
be done in the catchment - have a look at the various River Action
Plans that are available online - and they simply need the money to
implement these actions.
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