Issues

• Water Quality
• Water Quantity and Water Use
• Groundwater
• Health and Extent of Native Riparian Vegetation
• Aquatic Health
• Wetlands
• Wild Rivers

• Land Use and Inland Waters

At a glance

The issue

This Issue Report draws together the pressures and effects on Tasmania's inland waters from land use activities and management practices. Some of these have been identified in other issues within the Inland Waters and Wetlands, Land, Biodiversity, and Settlements Chapters. The State's inland waters include both surface and groundwater systems, such as rivers, streams, lakes, wetlands and aquifers. Each of these are intrinsically linked to their catchments, so that the pressures from land use activities and management practices within a catchment can result in significant effects on surface and groundwater resources.

There are many land use pressures on Tasmania's inland waters. They generally stem from the management practices of water extraction and storage for human uses (e.g. agriculture, drinking water and industry) and catchment land use activities like land clearing, agriculture, native vegetation conversion, industry and urbanisation.

The effects of water extraction and storage can include the alteration of river flows and groundwater levels to a stage that is not sustainable for dependent aquatic ecosystems and human use. Natural hydrological processes in a catchment can be disrupted, influencing both surface and groundwaters and their connectivity. Flow regimes are often a trigger for reproduction and any change to the natural regime can influence the reproductive cycles of affected flora and fauna species. In-stream structures such as dams and weirs often represent a physical barrier to fish movement, and sediment and nutrient transport. They can also create conditions that are more suited to algal bloom development or favour the establishment of introduced species. A changed flow regime through river regulation can also affect the geomorphology of river systems, for example, by changing channel width and rates of erosion and scouring.

Catchment land use activities can also result in many land use effects on surface and groundwaters. The occurrence of dryland salinity resulting from land clearance, for example, can lead to water salinisation. Land clearance can also increase the likelihood of soil erosion and the transport of excess sediment and nutrients into waterways. The conversion of native vegetation to plantation or crops can influence inland waters by affecting catchment water balances and hydrological processes. Inland waters are subject to pollution such as chemical and biological contaminants from sources such as wastewater discharges and industry. Urbanisation can increase water pollution from stormwater discharges and alter the amount and timing of run-off reaching surface and groundwaters. The introduction and spread of exotic plant and animal species can also have varied affects on the water quality and quantity, and aquatic health of inland waters.

This 'At a glance' section provides an overview of the issue of land use pressures and effects on inland waters. Some examples of pressures and effects, and management responses to these, are provided here, while more detailed information is available in the Land Use and Inland Waters Issue Report. Further information may also be obtained from related issue reports within the Inland Waters and Wetlands, Land, Biodiversity, and Settlements Chapters.

A number of recommendations that are relevant to the issue of land use and inland waters are also provided.

Favourable news

There have been a number of management responses since the last SoE Report that have helped to assess and alleviate land use pressures and/or mitigate their effects on inland waters in Tasmania. These initiatives are occurring within the major water framework for Tasmania, comprising the Water Management Act 1999, the State Policy on Water Quality Management 1997 (DPIWE 2001), Water Management Planning, and the establishment of Protected Environmental Values. A spread of example management initiatives across water related plans, strategies, programs, guidelines, codes, modelling and monitoring, as well as relevant initiatives for land use activities and management practices, are presented below.

• The establishment of three Natural Resource Management regions across the State with integrated Natural Resource Management plans to be developed.
   
• The development of Water Management Plans (e.g. Great Forester Catchment Draft Water Management Plan 2002-DPIWE 2002). For example, a process has been introduced to help protect remaining environmental flows, provide for down-stream users, and avoid the problems of over-allocation as part of the planning. However, there has been limited progress with the development of the water management plans across the State.
   
• Capping of surface water usage in the South Esk basin with further work done on the Great Forester River to cap use and prevent water creep. Proposals are being considered to extend this type of exercise Statewide. Installation of water meters has also occurred in the South Esk basin as part of water management planning.
   
• The development of various strategies including the Tasmanian Surface Water Quality Monitoring Strategy (DPIWE 2003), the Draft State Stormwater Strategy, the Wetlands Strategy for Tasmania Draft Discussion Paper (DPIWE 2000) and WeedPlan - Tasmania's Weed Management Strategy (Ministerial Working Group 1996).
   
• The Conservation of Freshwater Ecosystem Values Project run by the DPIWE began in 2002, and aims to provide for the conservation of key, representative aquatic ecosystems, and inform water resource planning, development and management.
   
• The National Environment Protection Measure for the Assessment of Site Contamination was implemented as a State Policy in 1999, which includes some criteria for groundwater investigation.
   
• Natural Heritage Trust funding has occurred for some significant 'on-the-ground' improvements. For example, through the Rivercare Program, the Devolved Grant Scheme, River Works and the Clean Quality Water Program.
   
• The development of a number of environmental guidelines relevant to inland waters, for example, Emission Limit Guidelines for point sources of pollution (e.g. sewage treatment plants, meat premises and pet food works, intensive animal husbandry activities, and fruit and vegetable processing activities) and Environmental Guidelines for the Use of Recycled Water (2002).
   
• Reviews have been undertaken of various codes of practice, for example, the Review of the Soil and Water Provisions of The Forest Practices Code (FPAC 1999).
   
• The monitoring and assessment of the effects of land use and management practices on inland waters and aquatic health in many catchments across the State through, for example, the Tasmanian component of the Australia Wide Assessment of River Health Program (2001) and the State of Rivers reporting.
   
• The introduction of changes through the Vegetation Management Policy Framework, including: TASVEG mapping of forest and non-forest communities, the Permanent Forest Estate Policy, and the amendments under the Forest Practices Amendment Act 2001 relating to forest clearance other than for forest harvesting.
   

Unfavourable news

Pressures

The principal threatening forces upon Tasmania's inland waters generally include: water extraction and storage (including the infrastructure - e.g. dams, weirs, etc) and catchment land use activities such as: land clearance and vegetation change; the use of fertilisers, pesticides and herbicides; physical alterations to drainage systems; pollution discharges and leaks; and the introduction of plant and animal pests. Examples of some of the data available to help measure these pressures are provided below.

• There has been an increase in dam numbers of all sizes since the last SoE Report in 1997 (907 dams approved). The DPIWE Water Information Management System had 5,516 existing dams registered in 2002 for irrigation, stock and domestic uses. Of these, 5,168 were in-stream, and approximately 1,191 additional in-stream dams were listed as proposed (see Water Quantity and Water Use Issue Report).
   
• Seven of the 19 Surface Water Management Areas in Tasmania have been assessed as highly developed (70% of area) in 2002 (broadly indicating where stress and limitations to water development exist in Tasmania) by the National Land and Water Regional Assessment (2002) (see Water Quantity and Water Use Issue Report).
   
• Based on the limited groundwater information available in Tasmania, the National Land and Water Resources Audit estimated that two of the 17 Groundwater Management Units/Unincorporated Areas (Sorell and Wesley Vale) would exceed their sustainable yield by 2020, and the St Marys Unit would be using up to 65% of its sustainable yield by 2050 (see Groundwater Issue Report).
   
• A number of catchments ranked poorly both in terms of containing a high percentage of their areas experiencing woody vegetation change (a measure of land cover disturbance) and a high percentage of their areas under modified land cover classes (such as agricultural and urban land cover), which can lead to significant flow-on impacts on inland waters. These catchments were the Cam, Inglis, Blythe, Rubicon, Leven, Montagu and King Island. The five catchments with the highest percentage area under urban and suburban land uses are Lower Derwent, Derwent Estuary-Bruny, Cam, Tamar Estuary, and North Esk (see Land Tenure, Land Use and Land Cover Issue Report).
   
• The reduction of the permanent forest estate by 62,831 ha between 1997-2001 as a result of forest conversion (mainly for agriculture or plantation), which has the potential to affect, for example, catchment hydrological processes and water quality (see Land Clearance).
   
• The reduction in condition of riparian vegetation as indicated in 1998, where 53% was categorised as moderately to substantially disturbed, and a further 29% had experienced minor disturbance, as assessed along approximately 39,000 km of Tasmania's major watercourses. In 2002, riparian vegetation within three of the nine bioregions was generally considered to be degraded and declining in condition, or have suffered species extinction due to threatening processes related to land use practices in six of the bioregions (see Health and Extent of Native Riparian Vegetation Issue Report).
   
• The area of salt affected agricultural land in 2000 was estimated to be 53,500 ha, which represents about 3% of Tasmania's agricultural land (i.e. private land). This is an increase of 8,500 ha from the baseline 1992 data, which was estimated to be 45,000 ha (see Salinity Issue Report).
   
• The south-west and Central Plateau are shown as areas susceptible to erosion as well as the intensively farmed areas in the north-west and Midlands (see Soil Erosion Issue Report).
   

Effects

The key effects on inland waters from the various land use activities and management practices in Tasmania include the following: changes in surface water and groundwater flows and levels; catchment balances and hydrological processes in general; natural levels of various water quality parameters; and the accumulation of pollutants. Each of these can, in turn, affect the geomorphology, habitat and ecosystem health of a water system and lead to problems for human water use and consumption. Examples of some of these effects (where information permits) are provided below.

• Some 22 rivers were identified as being under stress from water extraction during a typical dry summer (DPIWE 2001) (see Water Quantity and Water Use Issue Report).
   
• The recent Mineral Resources Tasmania assessment of borehole data ties in with the National Land and Water Resources Audit, which modelled future status of groundwater development. The data indicates that in certain areas (e.g. around Devonport) the static water level in boreholes is gradually falling. This is presumed to be a result of increased extraction and borehole construction, combined with land use change (DIER 2001).
   
• Surface water quality guideline exceedences occurred in numerous catchments across the State for turbidity, conductivity, pH and heavy metals. High exceedences for turbidity guidelines were generally focused around agricultural land, while heavy metal exceedences tended to occur in mining areas. These results, however, are potentially influenced by the greater sampling of sites within these areas, compared to less disturbed areas.
   
• Nineteen out of 24 planning and management catchment areas, where some surface water salinity testing had been conducted (out of a total of 48 catchment areas), contained water with levels greater than 800 µS/cm. The World Health Organisation's preferred limit for drinking water is 800 µS/cm. Twelve catchments reached levels above 1,500 µS/cm, at which adverse ecological effects are likely to occur (see Salinity Issue Report).
   
• Contamination of groundwater from landfill sites (both current operating sites and closed sites) is a significant environmental problem facing Tasmania. A study of the effects of waste disposal on groundwater quality identified groundwater contamination at six of the ten sites that were investigated. If this percentage is extrapolated to the 176 sites identified around the State, potentially up to 100 waste disposal sites may have contaminated groundwater (Ezzy 2002) (see Groundwater Issue Report).
   
• There is insufficient information available to identify priority areas with the potential for acid drainage from the disturbance of acid sulphate soils. The environmental impacts from existing impacts are also unknown. There is at present no monitoring and assessment of land use changes in areas hosting acid sulphate soils.
   
• There is no apparent information available on the nutrient loads within inland waters on a Statewide scale, and Tasmania does not currently have a formalised monitoring program that specifically targets algal bloom outbreaks within inland waters.
   

Uncertain news

Information requirements for understanding the pressures of water extraction and storage, and catchment land use activities and their effects on inland waters, are significant. Many of these requirements are discussed in other issue reports across the SoE Report. Examples of some of the uncertainties that hinder a more complete assessment are provided below.

• There is uncertainty in the number of all types of in-stream and off-stream dams and other structures, as well as dam capacities in Tasmania. There is also limited field checking and monitoring of the effects of new dams on water quality and environmental flows.
   
• The sustainable water yield has not been measured for 6 out of the 19 Surface Water Management Areas in Tasmania because estimates could not be finalised for Hydro-Electric Corporation catchments. As such, it is difficult to determine whether the increase in water use in Tasmania of 126% from 199 GL in 1983-84 to 451 GL in 1996-97 has had a significant impact on the State's inland waters without further assessment to clarify sustainable yields, and to assess the increase in relation to localised effects upon aquatic health.
   
• The hydrology and water use of small catchments is relatively unknown.
   
• There is limited information on irrigation methods, their efficiency, and the changes in methods that have occurred since the last SoE Report. The environmental implications of the measured consumption of water for irrigation (representing 59% of the total water use in the State for 1996-97) are, therefore, difficult to determine.
   
• There is uncertainty with the values reported for mean household water usage for Tasmania because of the poor availability of data on water consumption.
   
• Uncertainty exists in the information available on native forest clearance and the extent of deep-rooted vegetation, because of inadequate baseline data.
   
• Little is known about the clearance of non-forest native vegetation as there has not been a comprehensive assessment on a Statewide basis.
   
• There is uncertainty over the amount of change in native riparian vegetation species and communities and the extent of their reservation, particularly as there has been no Statewide mapping.
   
• The extent, severity and rate of soil erosion (that can lead to sediment input to waterways) was assessed on private land across the State in 1995 and reported on in the last SoE Report, but there has been no additional Statewide information available for the current report.
   
• There is only limited information on groundwater extraction, watertable depths and salinity in Tasmania, making it difficult to comment on trends and assess the potential links with land use activities and management practices. Some data are available through Mineral Resources Tasmania and the National Land and Water Resources Audit.
   
• Only half of the 48 planning and management catchment areas have had surface water salinity testing.
   
• Although there are some data on particular substance emissions released into inland waters as reported by the National Pollutant Inventory, it is currently not possible to identify trends from this source.
   
• The current limited numbers of catchments to be reported upon through State of the Rivers reporting prevents a Statewide assessment of land use impacts on waterways to date.
   
• It is currently unknown what level of monitoring there is across Tasmania for pesticide and herbicide exposure or pollution of inland waters and aquatic ecosystems. Data on fish kills across the State has also yet to be evaluated.
   

• Issue Report - continued in depth