Lower Limestone Coast Prescribed Wells Area Water Allocation Plan
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Water Allocation Plan for the Lower Limestone Coast Prescribed Wells Area Prepared by the South East Natural Resources Management Board Adopted 26 November 2013 Amended 10 December 2014 Amended 20 November 2015 Amended 29 June 2019 Water Allocation Plan for the Lower Limestone Coast PWA (June 2019) (This page left blank) Contents 1 The Lower Limestone Coast Prescribed Wells Area……………….…1 2 Assessment of the Needs of Water Dependent Ecosystems…...…..8 3 Assessment of Effects on Other Water Resources………….……....26 4 Assessment of the Capacity of the Resource to Meet Demands…32 5 Definitions and Abbreviations…………………………………………..76 6 Water Allocation Criteria - Unconfined Aquifer……………………...86 7 Transfer Criteria - Unconfined Aquifer………………………….…...117 8 Water Allocation Criteria - Confined Aquifer…………………….…125 9 Transfer Criteria - Confined Aquifer…………………………………136 10 Permits……………………………………………………………….……140 11 Monitoring, Evaluation and Reporting………………………………147 12 Consistency with Other Plans and Legislation……………………155 Appendix of Figures and Tables…………………………………………..156 1. The Lower Limestone Coast Prescribed Wells Area 1.1 Background to the Water Allocation Plan The aquifers of the Lower Limestone Coast (LLC) Prescribed Wells Area (PWA), located in the South East of South Australia, provide the region with large volumes of high quality water. However, this finite resource requires careful management to ensure that future generations can enjoy the lifestyle, economic prosperity and unique environment that water provides in the region. A Water Allocation Plan (WAP) sets out the rules for managing and taking prescribed water. The South East Natural Resources Management Board (the Board) is responsible for working with the community to develop and review water allocation plans for the region. This WAP is therefore pivotal in providing a clear direction that ensures the long term sustainability of the prescribed wells area’s water resources, which underpins the region’s people, townships, industries and environments. The LLC PWA was gazetted on 2 December 2004. The LLC PWA is the product of the amalgamation of the former Lacepede Kongorong, Comaum-Caroline, and Naracoorte Ranges PWAs. These last two areas were proclaimed to give effect to the requirements of the Groundwater (Border Agreement) Act 1985, with the aim to equitably manage the underground water along the South Australian/Victorian border, while Lacepede-Kongorong was proclaimed for the purpose of introducing structured resource management in response to potential over-allocation. The Board is at the forefront of change for water resources management, as an international leader in the introduction of a licensing system for the water requirements of commercial forestry. This Water Allocation Plan for the Lower Limestone Coast Prescribed Wells Area (the Plan) is the result of nine years of development by the Board (formerly the South East Catchment Water Management Board) in association with the community, industry groups and government agencies. The Plan is based on rigorous scientific research of the water resources of the area, combined with extensive community consultation and participation. Particular recognition must be given to the members of the Board’s LLC Water Allocation Plan Reference Group for their involvement in the development of the Plan. The LLC contains significant, often high quality, underground water resources in the form of unconfined and confined aquifers. A core objective of the Plan is to manage these resources for the continued social, economic and environmental benefit of current and future generations. The Plan protects the underground water resources to ensure its ongoing availability to sustain ongoing economic, social and environmental systems, while providing flexibility and equity of access to water. It sets out the principles for allocation, use and transfer of underground water in the LLC PWA. These principles will ensure that allocations are available to sustain economic development, while aiming to bring at-risk management areas back to environmentally sustainable levels of allocation. The Plan is made pursuant to Chapter 4, Part 2, Division 2 of the Natural Resources Management Act 2004 (the Act) and is consistent with the objects and requirements of the Act. The Plan is also consistent, where possible, with the Lower Limestone Coast Water Allocation Plan Policy Principles (Department for Water (DFW) 2012). The Policy Principles paper was developed in close consultation with a Stakeholder Reference Group, which included representatives of the dairy, dry-land farming, forestry, potato and viticulture industries, as well as representatives from the South Australian Farmers Federation and the Conservation Council of South Australia. The Policy Principles paper was developed to provide a basis for the preparation of the Plan; it consists of high level policy principles and more specific guidelines which have resulted from an extensive consultation process. The Act requires the Board to prepare a water allocation plan for each of the prescribed water resources in its region. The Plan replaces the Water Allocation Plans for the Comaum- Caroline, Lacepede Kongorong and Naracoorte Ranges PWAs adopted by the Minister for Water Resources on 29 June 2001 and subsequently amended on 14 October 2001. Water Allocation Plan for the Lower Limestone Coast PWA (June 2019) 1 1.2 The Prescribed Wells Area The LLC PWA covers an area of approximately 1,450,000 hectares. The PWA is bordered to the north by the Padthaway and Tatiara PWAs, and to the east by the state border with Victoria. It incorporates the city of Mount Gambier (population ~ 23,000), and the major townships of Naracoorte and Millicent (population ~ 5,000 each). The location and boundaries of the PWA are shown in Figure 1 (Appendix of Figures and Tables). The LLC PWA is the product of the amalgamation on 2 December 2004 of the former Comaum-Caroline, Lacepede Kongorong and Naracoorte Ranges PWAs. A number of confined and unconfined aquifer management areas in the LLC PWA are located within the Designated Area (Figures 2 and 3, Appendix of Figures and Tables). As a result, these management areas are under the jurisdiction of the Groundwater (Border Agreement) Act 1985. Under the Groundwater (Border Agreement) Act 1985, no new allocations should be granted, or temporary allocations renewed, where the limit to the volume of water to be extracted from licensed wells in the relevant Zone of the Designated Area would be exceeded. 1.3 Underground Water Resources The prescribed water resources of the LLC PWA consist of two distinct underground water systems, the upper unconfined Tertiary Limestone Aquifer (known generally as the unconfined aquifer) and the lower Tertiary Confined Sand Aquifer (known generally as the confined aquifer). Underground water is extracted from the unconfined and confined aquifers within the Murray Basin (northeast) and Gambier Basin of the Otway Basin (remainder). The Plan relates to all underground water in the PWA. 1.3.1 Unconfined Aquifer The unconfined aquifer consists mainly of calcareous sandstone and limestone. It incorporates the Gambier and Murray Group Limestones in the higher inland plains in the east of the region, and the younger Coomandook, Bridgewater and Padthaway Formations in the low-lying flats, which are interspersed with a series of northwest-trending remnant sand dune ridges. Underground water flow in the unconfined aquifer in the north east of the PWA is generally from east to west. Underground water flow radiates out from the Nangwarry/Tarpeena area in a northerly, westerly and southerly direction, that is, water flows approximately east to west throughout the northern three quarters of the PWA and from north to south in the lower South East. There are a number of major faults in the area which impact on underground water flow and gradient. The two most prominent are the northwest trending Kanawinka Fault and the west- northwest trending Tartwaup Fault, referred to as the Tartwaup Hinge. The water level and potentiometric contours of both the confined and unconfined aquifers indicate a significant steepening of slope immediately up-gradient of each fault. The thickness of the unconfined aquifer varies from ~10 metres thick north west of Mount Gambier, increasing to more than 300 metres thick south of Mount Gambier. The depth to water varies throughout the PWA relative to topography. Generally the depth to water is less than five metres on the plains, up to 20 metres in the ranges and more than 40 metres in the Mount Burr Range (Figure 12, Appendix of Figures and Tables). In the southern portion of the PWA there are numerous karst (dissolution) limestone features, of which Ewens Ponds, Piccaninnie Ponds and Hell’s Hole are examples. In general, underground water salinity in the unconfined aquifer increases from the south, where the salinity is less than 500 milligrams per litre (mg/L) Total Dissolved Solids (TDS), to the north, where the salinity is more than 4,000 mg/L TDS (South East Catchment Water Management Board (SECWMB) 2001a, 2001b, 2001c). Water Allocation Plan for the Lower Limestone Coast PWA (June2019) 2 1.3.2 Confined Aquifer The confined aquifers are separated from the unconfined aquifers by a low permeability aquitard (or confining layer), comprised mainly of glauconitic marl and dark brown carbonaceous clay. The combined thickness of the aquitard is generally more than 20 metres. The confined aquifer consists of non-calcareous quartz