What is Water Quality?
Water quality includes quantitative measurements of the physical
and chemical parameters of surface and wetland water in the BDT
region. Water Quality issues mostly originate from human activies
in the catchment area. Suspended solids including clays and
colloids and fine organic matter are a major impact upon the water
quality in the Burdekin Dry Tropics region. The long term average
sediment discharge is about 3.8 million tonnes, representing 20-40%
of the total sediment being delivered to the Great Barrier Reef
lagoon. Much of this occurs during cyclones or heavy monsoonal
rains and is the major impact of terrestrial runoff on near shore
environments of the Great Barrier Reef lagoon. Much of this is
delivered during infrequent floods with intervening years having
relatively low sediment discharge.
Impacts
Major impacts on ambient water quality include: increased
turbidity blocking sunlight and affecting ecological processes,
increased nutrient levels contributing to eutrophication and
decreased oxygen levels, low ph contributing to fish kills,
accumulation of contaminants in the food chain, sublethal
toxicological effects of pesticides, settlement of sediments, algal
blooms and weed growth.
Current Condition
Water quality has been identified as a central issue for the
Burdekin Dry Tropics region, whether the source is surface water or
groundwater. Both the marine and freshwater environments are
strongly affected by changes to flow and water quality as a result
of current land management practices and the use of water resources
(e.g. irrigation, urban development and mining).
Under the Reef Water Quality Protection Plan (RWQPP) 2003, the
Burdekin catchment has a risk profile classification of High with
respect to biodiversity, capacity to change, development pressures
and the risk to marine industries. Water quality is a pervasive
natural resource condition issue throughout the region and is
subject to a range of impacts including basin scale increases in
sediment and nutrient loading, turbidity, eutrophication, organic
loading, depressed oxygen levels and chemical contaminants. Key
impact distinctions exist between ambient and wash load water
quality, upper and lower catchment, river channel, floodplain,
coastal and surface and groundwater quality issues.
Water Quality Drivers
Surface water quality issues within the Burdekin Dry Tropics
have can be separated into three issues: Ambient water quality,
Bedload Events and Washload Events.
The chronic impact of ambient water quality is greatest as
baseflow ceases and rivers contract to a series of permanent
waterholes during the dry season. In addition to these effects,
there is evidence that the deterioration of water quality as a
result of cattle, pigs and brumbies loitering in waterholes may be
important in determining the health of aquatic ecosystems.
The severity of water quality degradation is high and includes
existing impacts andpotential risks to a host of regional assets
including downstream systems and biodiversity assets such as the
GBRWHA, coastal and floodplain wetlands including Ramsar sites and
protected areas, groundwater aquifers and irrigation and domestic
water supply infrastructure. Significant aquatic biota impacts
(fish kills and species loss) associated with water quality
degradation have been recorded in lower catchment floodplain
wetlands.