Thursday, January 05, 2006

Tasmania's wild rivers - mighty, free and full of poo?

Happy New Year!

My girlfriend and I have just returned from a great break in Tasmania. We stayed in Hobart most of the time with some side-trips across to the West Coast and down to the Huon Valley. We walked through the signature rainforests – huon pine, celery-top pine, sassafras and huge cool climate eucalypts such as the swamp gum – and crossed or travelled up the Huon, Franklin, Derwent and Gordon rivers and the huge Macquarie Harbour. Most of these rivers are a dark cola brown from the tannins from buttongrass on the highland plains at the rivers’ sources.

A little tragically, I was on the lookout for a hot environmental issue to write about here. Given Tasmania’s reputation for pristine wilderness and clean mighty rivers, it surprised me that the big issue in the news at the time was not old-growth logging or the cancer decimating Tasmanian devil population, but the fact that Tasmania’s main river – the Derwent – is not safe for swimming:
Public health authorities have welcomed efforts by the Hobart City Council to pinpoint what has polluted a popular swimming spot on the River Derwent. People are being advised not to swim at the Sandy Bay beach until further notice, because of faecal contamination.

Director of public health, Roscoe Taylor, says people risk contracting gastroenteritis, skin infections or respiratory disorders if they swim at the city end of Nutgrove Beach. He says it is hoped the beach will be safe by next summer but other beaches on the Derwent are more problematic. "It's very doubtful that Cornelian Bay will be up to swimming standard for quite a long time," he said.

The UN’s Atlas of the Oceans has this to say about the Derwent river estuary:
Named after the Celtic word 'clear water' in 1794 the Derwent estuary population has since grown substantially and now boasts 40% of Tasmania's population along its periphery. The estuary is an important and productive area with a variety of habitats including areas of wetlands, intertidal flats, kelp beds, seagrasses and rocky reefs that support a wide range of species, including black swans, oyster catchers, migratory bird species, penguins, dolphins and seals, platypus and seadragons [and] the critically endangered Spotted handfish...

As with many estuaries, local population growth has occurred resulting in estuary waters being used more and more for recreation, industry and marine transport. The upstream Derwent river provides the majority of the regions drinking water and is a source of energy via hydroelectric power stations. However these activities take their toll. Sedimentation has increased, there is heavy metal contamination, sewage problems, which together have lowered the oxygen level is some areas as nutrients have increased. Scallop dredging has destroyed seagrass and kelp beds, and kelp has been overharvested… large wetland areas in the upper estuary have also suffered recent degradation.

I reckon the health of rivers is one of the most widespread and intractable environmental challenges around the world. It’s something that environmental economics should be ideally placed to address because it’s about resolving conflicts over a common resource.

But what solutions does environmental economics offer to this? Is there any scope to create markets for river use? Is this something better left to planning law? Or is it something that should be looked after by government? How and who should decide what mix of uses a river should be put to? How do you resolve the competing claims on a river for drinking water, hydro power, irrigation, transport, recreation (swimming, fishing, boating), the protection of natural ecosystems, urban uses, industry, agriculture, forestry and so on?

Any ideas?


Cat said...

I was previously under the impression that one of the main pollutants of the river was Jarosite (one of the residues of the zinc refining process)dumped in the river by Pasminco, a zinc refinery positioned on the banks of the river. However, the CSIRO did a study and determined that there are no significant environment effects from dumping jarosite at sea (though there is no mention of rivers). I think Pasminco stopped dumping it in the river a couple of decades ago now anyway.
So it turns out it's mostly poo after all.

David Jeffery said...

Thanks Cat.

From a bit of looking around at some sites on this, it seems that heavy metal contamination is still an issue and the Pasminco zinc refinery is probably the main cuplrit.

RiverWorks Tasmania and the Federal Dept of Environment did a review of the Derwent's environmental quality in 1997. Their findings included:

"Contaminants enter the estuary from a variety of sources. Point sources include 13 sewage treatment plants and two large industries (a paper mill and zinc refinery), while diffuse sources include urban runoff, tips and contaminated sites, catchment inputs and atmospheric contributions. Some pollutants may also be derived from contaminated sediments within the estuary itself. There have been significant decreases in most end-of-pipe emissions over the past 5 to 10 years - particularly as a result of sewage treatment plant upgrades and improved treatment of wastewater from Australian Newsprint Mills - Boyer (ANM) and Pasminco Metals Hobart (Pasminco). At this point, the remaining of end-of-pipe emissions are derived primarily from ANM and from sewage treatment plants. Significant diffuse source inputs also enter the estuary, particularly from urban runoff ground-and surface-water emissions from tips and contaminated sites (particularly heavy metals from Pasminco) and the catchment as a whole (nutrients and sediments).

There have been some improvements in the water quality in the Derwent over the past 10 years, as a result of reduced end-of-pipe emissions from sewage treatment plants and industries. Some improvements in sediment quality have also been reported, including a reduction in sludge-affected areas downstream of ANM, and a decrease in some of the extreme heavy metal concentrations in sediments off Pasminco...

[In many] respects, however, the Derwent remains a highly degraded estuary - and it is difficult to predict if or when it will fully recover.

Heavy metals - particularly zinc, cadmium, lead and mercury - are the most severe and persistent problem, with concentrations in water, sediments and shellfish among the highest in Australia. Shellfish collected from most areas of the Derwent - particularly above the Tasman Bridge, the Eastern Shore and Ralphs Bay - should not be eaten. Human health issues aside, heavy metals undoubtedly also have significant toxic effects on the ecosystem, although this has not been quantified. Most troubling is the lack of substantial decreases in metal concentrations in sediments or biota, despite significant end-of-pipe improvements over past 20 years. It is unclear if this is due to continued diffuse source emission of heavy metals or to contaminated sediments continuing to release these metals over time."

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