Catchment issues
The Claise Brook Catchment Group is active within the
inner city of Perth including parts of the Claise Brook Catchment, the Perth
CBD Catchment and the Walters Brook Catchment. These catchments all drain
into the Swan River near the Perth city centre.
The present form of the Claise Brook
Catchment bears little resemblance to that of 1829, the time of European
Settlement. Much of the catchment was once an extensive system of lakes and
swamps from Lake Monger in the west to Claise Brook in the east. Many of the
lakes and swamps were interconnected during the wet season and drained into
the river through Claise Brook.
Today’s catchment is around 15km2,
being about 3km in width and approximately 7km from north to south. Lake
Monger is now part of a separate surface drainage system, but is affected by
groundwater movement from within the Claise Brook Catchment.
Most of the former surface water features have
disappeared, and the remainder are much altered to form artificial lakes
along the drainage lines. Parts of the drain intercept and drain high water
tables and can flow all year round, increasing the potential to transport
nutrients and contaminants to the river.
Residential use
is the dominant land use in the Claise and Walters Brook catchments and is
likely to be an important source of stormwater pollution, particularly
nutrients from garden fertilisers and pet faeces. Parks and recreational
areas are found throughout these catchments and potentially could contribute
contaminants as a result of pesticide and fertiliser application.
There are a wide variety of uses within
the commercial areas, and problems may arise from incorrect waste disposal.
This could result in a cumulative effect on water quality in the catchment,
particularly from restaurants, cafes and
hotels.
While the catchment historically included many industries,
this is now a minor land use occupying only 3.7% of the catchment area.
Former industries
The inner urban areas were formerly
Perth’s first industrial areas, particularly around East and West Perth, and
also North Perth. The trades included metal processors, auto and related
trades, timber trades, printers and public utilities. These trades involved
the use of a number of harmful contaminants which may persist in soils and
groundwater including trace metals, acids and alkalis, solvents,
hydrocarbons, pesticides, phenols and ammonia compounds.
To assess the degree to which past land uses may be
compromising catchment and river health due to soil and groundwater
contamination, in 2000 the group commissioned Jeanette Conacher to prepare a
report on the historic land uses within the Claise Brook Catchment. This was
funded by a grant from the Swan River Trust.
The “Historic Land Use Survey of the Claise Brook
Catchment” identified a number of sites or zones within the catchment which
are considered at high risk for soil and groundwater contamination. This is
based on land uses with high pollution risk and where the past activities
have been large-scale, enduring or known polluters. The report strongly
recommended in-situ soil and groundwater monitoring at 12 sites.
The report also identified a number of sites with a
pollution risk relating to nutrients, including diffuse sources from parks
and gardens and point source from historic landfill and nightsoil sites.
More recently concerns have been raised
about possible acid-sulphate soil problems in areas within the former
wetlands.
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This soil
map shows the location of the former wetlands, which occupied low lying land
between Lake Monger and East Perth. Only Lake Monger, Hyde Park, Queen’s
Gardens and Smith’s Lake remain as surface water bodies
Everyone lives in a catchment - click
here to find out
how to look after your catchment
To learn more about environmental
issues within the inner city, particularly relating to water quality, come
on a tour.
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