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Estuaries are partially enclosed bodies of water formed where fresh water from rivers and streams flows into the ocean, mixing with salty sea water. These transitional areas between land and sea are protected from the full force of ocean waves, winds and storms by the promontories, islands, reefs and sandy spits that mark an estuary's seaward boundary.
Estuaries, coastal wetlands and lagoons are vital elements of the coastal system. The combination of sheltered conditions and inputs from both marine and terrestrial sources means that wetlands, salt marshes, intertidal seagrass meadows and other foreshore flats inside coastal inlets are particularly rich in the variety and abundance of species of plant and animal life. The sheltered, tidal waters of estuaries support unique communities of plants and animals, specially adapted for life at the margin of the sea. Estuarine environments are among the most productive on earth, producing more organic matter per year than equivalent areas of forest, grassland or agricultural land. Their high productivity results in large populations of invertebrates, fish and birds. These areas act as nurseries for many marine species and their high productivity concentrates flora and fauna. They are also diverse in geomorphic terms. A wide range of habitat types is found in and around estuaries. In temperate regions such as Tasmania, these include beaches and dunes, rocky foreshores, marshes and other wetlands, mud and sand flats, seagrass meadows, kelp forests and rocky reefs. The variety and productivity of these estuarine habitats support a wonderful abundance and diversity of plants and animals, which are linked to one another through complex food webs. Estuaries are under increasing human pressure as they are important sites for human settlement, tourism and recreation. Oceans and estuaries also operate within many jurisdictions and under multiple forms of management. Serious disturbances to these environments may occur as a result of changed nutrient status or increased loads of sediment. Increased nutrients may cause phytoplankton blooms. In extreme cases, the blooms can dominate a system and out compete attached species under the bloom for light and nutrients. The waters change from one stable ecological state (macrophytic) to another (planktonic). Phytoplankton blooms deplete dissolved oxygen in the water column, which can lead to fish kills and species loss. This process of 'eutrophication', apart from damaging the ecological state of the environment, can also result in severe odour problems and a general loss of amenity of the area. The major estuaries, together with Macquarie Harbour, some east coast lagoons and Orielton Lagoon, have the most degraded coastal marine environments in Tasmania. These water bodies receive run-off from agriculture, forestry, mining, industry and towns. The quality of Tasmania's estuarine waters is integral to the economic, social and environmental sustainability of the resource. Clean and safe water is also crucial to safeguarding the health of recreational users. The same is also true for the environment. Healthy waterways are necessary for the variety of aquatic habitats, and the systems that rely on them, to be maintained. Tasmania has 111 moderate to large estuaries along its coast; some of the larger and better known include the Derwent, Tamar and Huon rivers, Port Davey and Macquarie Harbour. The issue of reduced estuarine water quality is mainly orientated around those areas where mining, urban, industrial, forestry, hydro-electric dams and agricultural land uses have resulted in degradation.
Estuary reviews - a regional perspective The Environment Division of DPIWE has prepared reviews of estuarine condition and health, updating the previous SoE Report (SDAC 1997). These include reviews of: River Derwent, River Tamar, Huon River, Macquarie Harbour, Burnie (coastal waters), and the Mersey Estuary. Summaries of estuarine reviews follow. River Derwent The estuary of the River Derwent occupies a drowned river valley. Extending for a distance of 52 km from New Norfolk to the Iron Pot, the estuary has a surface area of 198.4 km2. Within its 8,900 km2 catchment live around 175,000 people, mostly in the greater Hobart area. The Derwent Estuary's catchment comprises the Derwent River catchment (7,764 km2), the Jordan River catchment (742 km2) and other areas adjacent to the estuary, including Ouse and Clyde River catchments (375 km2). The catchment itself is a mixture of agricultural land (50%), State and private forests (24%), national parks (18%) and urban areas. The water column of the estuary is mostly stratified (layered), with a distinct freshwater layer flowing over a denser salt-water 'wedge', although this varies, with the water in some places being partly mixed. Salt water on the bottom of the estuary can penetrate to a few kilometres upstream of the town of New Norfolk. The tidal range of the estuary is only 1 m. On a naturalness index basis the Derwent Estuary is classified as being moderately impacted on an estuarine catchment area basis and highly impacted on an estuarine drainage area basis (Edgar et. al. 1999). The Derwent estuary has a number of environmental issues, specifically heavy metal contamination, elevated nutrient concentrations, depressed dissolved oxygen (DO), organically enriched sediments, introduced marine pests, loss of estuarine habitat and species, intermittent faecal contamination of recreational areas, and adequate environmental flow and existence of physical barriers to fish migration. The Derwent remains a significantly degraded estuary. Significant strategic and co-ordinated management is being achieved through the Derwent Estuary Program (DEP) established in 1999 as a partnership to restore and protect the Derwent Estuary. In December 2001, the DEP Environmental Management Plan was finalised and endorsed by the Premier, the Mayors of councils of the greater Hobart area, and the Commonwealth. A five year agreement was then signed to progressively implement this plan. Key aspects of implementation include environmental monitoring and reporting, coordination of regional activities, and implementation of priority projects such as effluent reuse, stormwater management and habitat mapping and restoration. Longer-term trends, since 1996, indicate a sharp decrease in faecal bacterial loads (>90%) and heavy metal loads (>50%), a decrease in TSS loads (17%), and an increase in nutrients (8% DIN, 17% TP) and BOD (15%). During the past three years, most sites have met recreational water quality guidelines for primary contact - particularly the main recreational beaches south of the Tasman Bridge. Long-term data sets for heavy metals suggest significant decreases in water column concentrations of zinc, cadmium and other metals over the past 30 years, but zinc levels at mid-estuary sites are still above recommended ecological guidelines. The majority of sediments within the Derwent are fine-grained and organic-rich and do not meet sediment quality guidelines for a number of heavy metals, particularly for mercury (99% of area in excess of guidelines), lead (87% in excess), zinc (68%) and cadmium (64%). Recurrent sediment surveys conducted in New Town Bay also indicate high levels of cadmium, mercury and zinc. Heavy metals in Derwent Estuary shellfish have been monitored by Pasminco for 11 years. Levels are well above the national guidelines-particularly for zinc in oysters and lead in mussels - with highest values in the area above the Tasman Bridge, followed by Ralphs Bay and then the Eastern Shore. A detailed sub-tidal habitat survey showed that most of the Derwent seafloor is characterised by unvegetated, soft sediments (96%). There are however, important macrophyte beds (underwater grasses) in the upper estuary, rocky reef habitats in the lower estuary, and some scattered seagrass beds in the middle and lower estuary. Over 20 introduced marine species have been identified in the Derwent Estuary and there are probably many more unrecorded species. Of the marine pests the northern Pacific seastar (Asterias amurensis), Japanese seaweed (Undaria pinnatifida) and toxic dinoflagellate (Gymnodinium catenatum) are of greatest concern. Further information on the Derwent Estuary is also available through the recently released State of the Derwent Report. River Tamar The Tamar Estuary, situated along Tasmania's northern coastline, is one of the State's larger estuaries (100 km2), extending approximately 70 km from the City of Launceston, at its head, to Bass Strait. The estuary is tidal to the First Basin on the South Esk and to St. Leonards on the North Esk. Tides are predominantly semi-diurnal (two tides per day of approximately equal magnitude), being influenced by the strong semi-diurnal nature of the tides within Bass Strait (Foster et. al., 1986). Tides in the Tamar Estuary are amplified in the upper reaches, with the mean tidal range gradually increasing from 2.34 m at George Town to 3.25 m at Launceston. The large tidal range suggests that tidal mixing plays a relatively important role in the estuary's hydrodynamics. The estuary has strong tidal currents and is partially/well mixed having salt wedge characteristics in the upper reaches. The Tamar is a narrow estuary with a deep, well-defined channel, bordered by shallow tidal mud flats and wetlands. The main channel in the lower estuary reaches 45 m in depth near Bryants Bay (Hydrographic Branch, Department of the Navy, 1967). However, the combination of a large sediment load from the catchment and strong tidal currents has resulted in rapid sedimentation in upper reaches of the estuary above Swan Point becoming very shallow as the estuary nears Launceston. This has resulted in a long history of dredging. The tidal mud flats and wetlands in the middle and upper reaches have been colonised by the invasive rice grass Spartina angelica. A diverse and productive ecosystem is characterised by the 3 m tidal range and large freshwater inputs from the North and South Esk Rivers. On a naturalness index basis the Tamar Estuary is classified as moderately impacted on an estuarine catchment area and estuarine drainage area basis (Edgar et. al. 1999), but is classified as Class A (critical conservation significance). This Class A is justified because it is the only estuary of its type (mesotidal drowned river valley) in Tasmania. It possess extremely high plant, invertebrate and fish diversity and it possess a large number of species not recorded elsewhere (Edgar et. al. 1999). The Tamar's catchment is very large at 10,000 km2, of which the South Esk Basin (consisting of the Macquarie, Meander and South Esk sub-catchments) occupies the majority, while the North Esk basin covers only 500 to 600 km2. The South Esk River is the longest river in Tasmania, being 214 km long. It is the main source of freshwater flows and sediments to the Tamar. Mean annual flows of the South Esk Basin are 70 cumecs. Mean annual flow of the North Esk catchment approaches 10 cumecs. The flow characteristics of the South Esk (and Macquarie) Rivers are greatly influenced by the operations of the Trevallyn/Poatina Power Scheme, which generates hydro-electric power in the Tamar catchment. Most of the land in the catchment is used for agriculture (52%) and forestry (37%), with some national parks in the more distant regions. Many urban and industrial uses are concentrated near the estuary's shore. The City of Launceston (population 59,000 ABS 2001) is at the head of the estuary. Other large towns in the catchment include George Town, Perth, Deloraine, Westbury and Longford. The Tamar estuary is impacted by human activities (urban and agricultural run-off, sewage and industrial discharges and indirectly drainage from mine sites) producing contaminants such as pathogens, hydrocarbons, metals, organic matter, nutrients and sediment, and introduced marine pests (rice grass, East Asian bag mussel, and the pacific oysters). Historic activities have created a legacy of contamination of sediments and possibly groundwater. The estuary receives inputs of sediment from the South and North Esk River catchments, which through the action of tidal currents tend to accumulate as fine-grained silt deposits in the upper reaches of the system requiring dredging. Heavy metals, particularly zinc, cadmium, lead and copper appear to be elevated in several areas of the Tamar, notably the upper estuary around Launceston and lower estuary in Deceitful Cove and Middle Arm. Sediment analysed indicated contamination for total arsenic, chromium, copper, lead and zinc at a number of sites. Concentrations of all metals in Deceitful Cove were elevated over background levels. Also Middle Arm exhibited high levels of arsenic, copper, zinc, and mercury where with the exception of zinc (just below the standard) all exceeded the sediment standard. In the upper estuary the levels indicated historic metal contamination. Specifically chromium, copper and zinc exceeded the sediment standard. Zinc and copper levels were high at Gravelly Beach. Samples of sediments from Rosevears, Red Bay and Long Reach were generally clear of contaminants. The mid-depth water sediment traps captured sediment with high levels of heavy metals: lead and zinc in the sediment exceeded the standard. The levels of heavy metals in shellfish, specifically zinc and copper, from the estuary are in excess of the recommended Australian and international guidelines and it has been recommended that oysters collected in the estuary should not be eaten. Nutrient inputs from the STPs and agricultural and urban stormwater run-off are potentially significant, but Tamar is not presently known to experience algal blooms. The levels of total phosphorus and nitrogen recorded quarterly over the last few years are above the default trigger values in the ANZECC 2000 guidelines in the upper estuary for further investigation. Considering the Director of Public Health Reports (annual) since 1999 all identified sites where primary contact may be undertaken during the swimming season (December-March) were considered suitable. The faecal coliform median values from quarterly sampling for the estuary over 1999-02 in the upper estuary at the Tamar Yacht Club, though, exceeded the recreational primary contact level (150 faecal coliforms/100mL). This value however is an improvement over the values in State of the Tamar Report 1997 which exceeded the secondary recreational contact level (>1,000 faecal coliform/ 100mL). The estuary is unfortunately severely impacted by introduced species including rice grass Spartina angelica (colonised in tidal mud flats and wetlands in the middle and upper reaches), East Asian bag mussel Musculista senhousia, and the pacific oysters Crassostrea gigas. Huon River The Huon River and estuary in south-eastern Tasmania is a typical drowned river valley, which runs into the sheltered waters of the D'Entrecasteaux Channel between the Tasmanian mainland and Bruny Island. It has not changed substantially from its historic baseline. The estuary covers about 77.4 km2 (of which 35 km2 is the Huon River upstream from Beaupre Point) and is fed by a catchment of about 3,130 km2. On a naturalness index basis the Huon Estuary is classified as 'natural' on an estuarine catchment area basis and 'lowly impacted' on an estuarine drainage area basis (Edgar et. al. 1999). The mouth of the estuary is 20 km from the Southern Ocean in the south. The main population centres of Huonville, Cygnet, Geeveston and Franklin are on the estuary shores but the region has always been sparsely settled. The total population for the region is around 13,000. Diversion of Huon River head waters for the past two decades above Scotts Peak Dam for hydro-electric power generation has reduced the annual Huon River system median flow by 15% (from 3,000 to 3,600 million m3) and the low flow by 8% (Livingston 1995). The Mountain and Kermandie Rivers are the largest tributaries to the Huon River but only amount to 3% of the Huon flow at Judbury. The average annual rainfall varies from over 2,000 mm in the west of the catchment to approximately 800 mm in the east. The rainfall is relatively uniform peaking in July to October. The estuary is about 39.1 km long, with a maximum depth of 55 m in the deeper marine zone in the lower half of the estuary but becoming as shallow as 5 m upriver of Port Huon in the brackish zone of the upper half of the estuary. The estuary has a third geographic zone identified as the Port Cygnet Arm, which is shallow and marine in nature. The Huon Estuary is characterised as a micro salt-wedge estuary (CSIRO 2000). The estuary is strongly stratified with the marine bottom layer penetrating as far as Ranelagh on occasions under low river flow. The Huon River flows consistently throughout the year and drives a two-layer estuarine circulation. The fresher layer flows seaward over the marine bottom layer, which moves very slowly upstream. The hydrology of the estuary is characterised by a fast flushing time whereby the surface layer leaves the estuary in hours to days and the whole water column in days to one week. The turbidity is low however coloured dissolved organic matter attenuates the penetration of light. The currents and tidal currents are generally weak (<0.2 m/s). The estuary is sourced by two very high quality waters namely the Huon River and the coastal waters of south-east Tasmania. It generally has a high quality but there are natural and anthropogenic pressures that do influence the water quality in the estuary. Specifically the degraded water quality of some tributaries in the lower catchment, probably due to unsustainable land use, is having only localised impacts at this stage. Also low DO and elevated nutrients, ammonia and nitrite, are acting as potential stressors. The low DO is in deep holes in the upper estuary and on occasions in the bottom waters in the lower estuary. This low DO is a result of a high proportion of organic matter either from terrestrial plants in the upper estuary or phytoplankton production in the middle and lower estuary. Also in the bottom waters of the lower estuary elevated ammonia and nitrite levels occur after outbreaks of dense microalgae (CSIRO 2000). Nutrients in sediments are being recycled and released back into the water column making the estuary vulnerable to increases in nutrient load. The estuary in general has a good water quality. It has two principle inputs, the Huon River and seawater which are both of a high environmental quality. The Huon Estuary Study (CSIRO 2000) recommended that the upper Huon catchment should be carefully maintained to protect this main source of freshwater into the estuary. The land in the catchment is used primarily for national parks (51%), forestry (22%) and agriculture (7%). To date, the sewage and industrial discharges have not adversely affected the longer-term water quality of the wider estuary. The Kermandie River, Agnes Rivulet, and Nicholls Rivulet and Prices Creek, to a lesser extent in the lower catchment, are degraded by high concentrations of SPM, nutrients and faecal coliforms. This is as a consequence of through agricultural activities, STPs and seepage from domestic septic tanks. In the stratified Huon estuary, the surface layer receives most of the leachate and effluent from the catchment. Naturally high nutrient levels are connected with marine nitrate and phosphate from the continental shelf waters. About half of the bio-available nitrogen enters via the estuary in the bottom waters at the marine boundary, while the other half comes from primary industry activities, agriculture and aquaculture. The marine nutrients drive phytoplankton blooms in spring, summer and autumn, where diatoms and dinoflagellates alternate over this period. CSIRO (2000) predicted through modelling that if the 1997 finfish loads were doubled this would increase the risk of increasing frequency and density of summer phytoplankton blooms. With four times the load the system would be on the brink of nitrogen saturation and at significant risk of prolonged blooms. A more recent preliminary survey of trace metals in sediment and water, as part of Huon Estuary Study (2000) showed no levels that were above the national guidelines. Organic enrichment of the sediment on the floor of Hospital Bay and partly in the main arm of the estuary has resulted from sawmill and pulp mill waste entering into the bay from Whale Point most of last century. The Huon Estuary Study 2000 although limited found no evidence in the estuary of past use of inorganic pesticides such as lead arsenate and copper salts. However persistent organo-chlorine pesticides, DDT and DDD, were found in high concentrations in Hospital Bay sediment. The sediments under aquaculture leases are polluted from fish and shellfish faeces and an 11 months fallow period is required for the geochemical conditions to return to those at the reference site. The benthic fauna may still consist of opportunistic species though, indicating a failure to return to baseline. Toxin producing dinoflagellates Gymnodinium catenatum, were responsible for closure of shellfish sites in the Huon Estuary and neighbouring waters during autumn, and extending into winter, in 2002. Macquarie Harbour is Tasmania's largest estuarine system, at 290 km2 in area. It is also one of Australia's largest estuaries. It is an enclosed embayment with very restricted water exchange with the Southern Ocean. The harbour is approximately 33 km long and 9 km wide, and is generally narrow and shallow, with the exception of a deep depression 5-10 km south of the King River mouth where the depths can exceed 50 m. This water body lies in a large geological trough (graben) blocked to the north by Tertiary and Quaternary sediments. The mouth of the harbour (Hells Gates) is very shallow (about 4 m deep) and narrow, due mainly to large amounts of sediments carried southwards along Ocean Beach. The harbour's tidal range is less than 1 m, but despite the harbour's small entrance, tidal flows are large due to the surface area involved. On a naturalness index basis the Macquarie Harbour is classified as natural on both an estuarine catchment area and estuarine drainage area basis. (Edgar et. al. 1999). The main freshwater inputs and influences on the circulation patterns in Macquarie Harbour are from the King and Gordon Rivers, both regulated by Hydro dams. The rivers have been identified as being subject to changes under the Basslink proposal to connect the Tasmanian electricity system to the National electricity market. The Gordon River provides about five times the contribution of the King River on a yearly basis, with the mean flow of 265 m3/s or 9 km3/yr and the King River at 55 m3/s or 1.8 km3/yr. Numerous smaller streams also flow into the harbour. In the northern harbour heavy metals coming from the Mt Lyell copper mine over the last 100 years continue to be the primary source of contamination of copper, aluminium, zinc and other metals entering the harbour from the King River. The contaminants are dispersed by wind mixing and currents. Generally all three populations in Macquarie Harbour-benthic invertebrates, fish, and phytoplankton-are depauperate because of mining inputs. The copper concentrations within the sediment and the organic content of the sediment were found to be the likely factors controlling the population structure of the benthic community. The vast deposits of highly contaminated sediment will remain an impediment to recovery of the benthic invertebrate communities even if the water quality of the harbour is improved. The high metal concentration distribution in Macquarie Harbour in July-September 2001 was the result of acid drainage input into the Queen/King River exacerbated by a combination of factors. These included a relatively dry summer/autumn being followed by near record rainfall in June 2001 (and subsequent rain), relatively calm winter wind conditions, and thick fresh water layer in the Harbour typical in winter. Copper and zinc concentrations in native fish are well below Australian Food Code guideline values. Also average values for mercury and selenium were below the guidelines but there were a few individual fish with levels were greater than the guideline values. Copper concentrations in oysters were 25-30 times greater than the guidelines and the zinc values were 30% over the guideline limit. However the concentrations in mussels were found to be below the guideline values. On the basis of mercury levels, a health warning was given in 1993 to limit consumption of native salmon and other fish to 1 fish per week. Based on current uses and values, the five zones in the harbour can be used for harvesting of fish and crustacea but not shellfish except for Zone 5 (bounded by Spur Point and Yellow Bluff and Macquarie Heads) where shellfish can be harvested. Assessing and measuring the current situation The water quality of estuaries is highly variable over space and time. Such variation in water quality is affected by factors such as tides, weather patterns, water quality of inflowing rivers, season, vegetation and surrounding land uses. Human settlements have had a significant impact upon estuaries through discharge of industrial waste and treated sewage waters, urban and agricultural run-off, and infestation of exotic pests through shipping. Estuaries are also impacted upon by recreational and professional fishing and, increasingly, through providing sites for the farming of fish and shellfish. A recent study conducted by the Tasmanian Aquaculture and Fisheries Institute (TAFI) has sought to assess water quality in Tasmanian estuaries (Murphy et al. 2003). Major objectives of the study were to provide baseline water quality data and determine water quality indicator levels for Tasmanian estuaries. State of the Environment and ANZECC have both identified a lack of baseline data as severely limiting our ability to set appropriate trigger values for indicators of estuarine health. Determining baseline values is seen as the first step in the detection and possible remediation of environmental problems affecting Tasmanian estuaries. In the TAFI study, water quality parameters were measured at 22 Tasmanian estuaries. The estuaries included in the study were chosen to reflect a range of physical estuarine groups (e.g. barrier, river, inlet, lagoon), estuaries of different conservation significance (Edgar et. al. 1999) and location within biogeographic regions. In addition, potential relevance to government agencies and community groups, as well as accessibility, influenced the selection of estuaries. Large, previously studied estuaries such as the Derwent, Tamar and Huon rivers and Bathurst and Macquarie Harbours were deliberately not included in the study. Due to accessibility, estuaries in the south-west of the State and the King and Furneaux islands were not included in the study.
The TAFI study sought to recognise the recommendations of the ANZECC (1999) guidelines for water quality monitoring and assessment when establishing sampling protocols. To assist in determining the location of sampling sites, a pilot study of water quality parameters was conducted within each estuary. Based on the results of the pilot study, and geographic features that were interpreted as likely to influence flows, six fixed sampling sites were selected within each estuary (only four sites were chosen in the Don and Nelson Bay Rivers). The TAFI estuarine health study was conducted between July 1999 and June 2000. Each estuary was sampled once every two months, a total of six sampling events at each estuary. Sampling was conducted as close as possible to the time of low tide. The water quality parameters measured at each site were salinity, temperature, dissolved oxygen (DO), turbidity, chlorophyll a, nutrients (NOx-N, PO4-P, SiO4-Si) and suspended solids. Salinity, temperature and DO were measured at a range of depths between the surface and the bottom, the exact depths depending on water depth within each estuary. For the other parameters, a water sample was taken from just below the surface and analysed in the laboratory. For each estuary, statistical analyses were conducted to determine whether there was vertical and horizontal stratification and/or differences over time for each of salinity, temperature and DO. Climatic conditions during the study period were characterised by relatively low rainfall across most of Tasmania, particularly during much of summer and autumn 2000. However, sampling was also undertaken following some large flood events. Floods occurred on the central north coast (Don and Mersey rivers, Port Sorell) in early August 1999 and on the north-east coast (Ansons Bay, Grants Lagoon, Douglas River) in mid-January 2000. Heavy rainfall also preceded sampling in the south-east (Browns and Catamaran rivers, Cockle Creek) in mid July 1999. Therefore, for most estuaries, sampling covered a broad range of conditions that would generally be experienced over a longer time scale. Salinity data obtained from the TAFI study reinforced the consensus that estuaries are highly variable systems, with salinity profiles often unique to each estuary. Vertical stratification was seen in most estuaries and was very distinct in river estuaries, particularly the large, deep estuaries on the west coast (Arthur and Pieman) and small, east coast river estuaries (Douglas, Meredith, Browns and Catamaran). The upstream section of Ansons Bay was also highly stratified. The estuaries that were not vertically stratified were generally open, marine inlets (East Inlet, Port Sorell, Great Swanport, Little Swanport and Cloudy Bay) or shallow, low salinity estuaries (Boobyalla Inlet and Nelson Bay). While not all estuaries showed vertical stratification, salinity differences along the length of the estuary were recorded for all the study estuaries. The greatest vertical stratification and horizontal variation was seen in the upper sections of each estuary. National State of the Environment reporting identified key environmental indicators for estuaries and the sea. It determined that nitrogen, chlorophyll and turbidity were important indicators of ecosystem health and that routine monitoring of estuarine water quality should include these parameters (Ward et al. 1998). The table shows average (each sampling event) and yearly median values for these three key parameters, from surface waters, for each estuary. ANZECC (2000) default trigger levels for estuarine water quality contain no Tasmanian data. Therefore, draft indicator levels, referenced against the baseline values from the TAFI study, are provided for Tasmanian estuaries in the second table. Draft indicator levels are based on the likelihood of exceeding these values during a single sampling event, using data from all estuaries. Depending on the scale of future studies, alternative indicator levels could be based on a bioregional or estuary scale. However, given data are from surface waters and vertical stratification occurs in most estuaries, indicator levels should be applied with caution to samples taken from other depths. |
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Chlorophyll Concentrations In Tasmanian Estuaries - at a glance
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Turbidity In Tasmanian Estuaries - at a glance
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Water Nutrients (Nitrogen) In Tasmanian Estuaries - at a glance
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Exceedences of Water Quality Guidelines: Coasts and Estuaries - at a glance
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Environmental values for coastal waters are yet to be set. It is anticipated that coastal water environmental values will be set during 2003. Following the setting of environmental values, water quality objectives (standards) for the protection of these values will be determined. The objectives will provide a benchmark by which the success of natural resource management plans can be tested. Tasmania Together and the RMPS Relevant Tasmania Together goals and standards for 'Coastal, Estuarine and Marine' are listed in the linked file. The Tasmania Together Progress Board reported on progress toward targets for benchmarks set (Tasmania Together Progress Board 2003). Indicators, targets and baseline data are available in the latest Progress Report June 2003. Further information, including progress report updates, is available from Tasmania Together. Involvement of the community, and the fair and orderly use of resources are also fundamental principles of the RMPS. The RMPS objectives have been developed to advance the principles of sustainable development.
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