Upper Lachlan Alluvial (Groundwater) Management Zone 1

Background

The orders are to address declining groundwater levels in the Upper Lachlan Alluvial Zone 1 Management Zone of the Upper Lachlan Alluvial Groundwater Source. The restriction order and Access Licence Dealing Principles (ALDPs) order are appropriate to protect groundwater levels and likely impacts on access for critical needs, groundwater dependent ecosystems and to prevent in the aquifer.

Reason for decisions

Temporary water restriction – section 324
Access Licence Dealing Principles – section 71Z

Section 324(2) of the Water Management Act 2000 (the Act) allows the Minister or delegate to order that a temporary water restriction on the taking of water from an aquifer is to have effect for a specified period within a specified area, if satisfied that it is necessary to do so to:

• maintain or protect water levels in an aquifer, or
• maintain, protect, or improve the quality of an aquifer, or
• prevent land subsidence or compaction in an aquifer, or
• protect groundwater-dependent ecosystems, or
• maintain pressure, or to ensure pressure recovery, in an aquifer.

Trade restrictions are required to complement the temporary water restriction. Section 71Z of the Act allows the Minister or delegate to, by order, establish ALDPs to regulate or prohibit the kinds of dealings that may be affected under Division 4 of Part 2, Chapter 3 of the Act.

I am satisfied that it is necessary to apply the temporary water restriction order to restrict take from the Upper Lachlan Alluvial Zone 1 Management Zone of the Upper Lachlan Alluvial Groundwater Source for the following reasons:

• to maintain or protect water levels in the aquifer – groundwater levels have declined below threshold levels which trigger a management response consistent with the NSW Extreme Events Policy and the draft Incident Response Guide for Groundwater Resource Plan Areas. The attached hydrograph shows water level decline in monitoring bore GW036500/2 has been below the ‘management response’ level of 25 m below ground for much of the second half of 2018/19, and again in the first half of 2019/20. In addition, on two occasions (late August / early September, and late October / early November 2019) it has almost breached the ‘unacceptable’ level of 27.3m below ground. Although the water levels recovered in November 2020 it breached the ’management response level’ of 25 m below ground in again January 2021.These levels have been set in consultation with landholders, and the unacceptable level approximates 40% of the total available drawdown in the aquifer consistent with existing government policy.
• to prevent land subsidence or compaction in the aquifer – retaining moisture in the aquifer prevents irreversible compaction of the aquifer sediments. Compaction reduces storage capacity and yield, diminishing the long-term yield of the affected water source. The Risk Assessment for the Lachlan Alluvium Water Resource Plan Area (Schedule D of the draft Lachlan Alluvium Water Resource Plan Area) identifies the Upper Lachlan Alluvium has having compressible sediments comprise 50-80% of the aquifer’s thickness and as such has a medium risk of sediment compaction as a result of groundwater level decline.
• to protect groundwater-dependent ecosystems – declining groundwater levels threaten the survival of groundwater dependent ecosystems within the zone as water moves beyond the zone of access. The Risk Assessment for the draft Lachlan Alluvium Water Resource Plan Area (Schedule D of the Lachlan Alluvium WRP) assesses the overall risk to impacts on groundwater dependent ecosystems associated with local water level drawdowns in the Upper Lachlan Zone 1 management zone as high. Note that local drawdown reduces groundwater availability through lower groundwater level. This results in reduced access by groundwater dependent ecosystems or reduced discharge to connected streams. This may impact the health of groundwater dependent ecosystems or instream ecological values in these areas of local drawdown.

The trade restriction ensures that users subject to the temporary water restriction can trade any allocations they do not extract but cannot trade or extract more than the capped limit. This ensures that water within the cap restriction can be traded within the management zone to those users who intend to extract. Together with the section 324 order, the Access Licence Dealing Principles order will ensure that extraction within the management zone is limited to 30% of the total share components within the zone.

Accordingly, the section 324 order and the Access Licence Dealing Principles order have been made to:

• Allow for groundwater level recovery,
• Prevent aquifer compaction
• Protect groundwater dependent ecosystems
• Retain water to meet critical human needs, and
• Allow some continued access to enable economic activity.

Chief Operating Officer
25 June 2021

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