Monday, January 12, 2015

First, understand the history of the Vasse and Wonnerup Estuaries and the Lower Vasse River. Only then can you better manage these waterways.

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 (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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