Water Resource Plan Targeted Consultation – Peel Alluvium (Cockburn River Alluvium Management Zone) Department of Industry – NAMOI ALLUVIUM WRP - June 2019
Background • Water sharing plans are the primary legal framework for managing water access and sharing in the Murray-Darling Basin. • Water resource plans are a requirement under the Basin Plan 2012 . • New ‘ Water Sharing Plan for the Namoi Alluvial Groundwater Sources 2019 ’ • will cover all alluvial groundwater resources of the Namoi and Peel valleys • replaces the Water Sharing Plan for the Peel Valley Regulated, Unregulated, Alluvium and Fractured Rock Water Sources 2010 - Peel Alluvium groundwater source • DoI Water proposes to update access rules to manage the surface water/groundwater interaction in the Peel Alluvium (Cockburn River Alluvium Management Zone)
Current Water Sharing Plan Rules • To manage the potential impact of groundwater pumping on the Cockburn River during low flows, the water sharing plan: • Links daily access rules for groundwater pumping to the surface water cease to pump rules, but with a 28 day delay from when the cease to pump conditions are triggered and applied to surface water users. o Surface water users must cease-to-pump when river levels are at or below 0.25m at the Kootingal Bridge Gauging Station. o The 28 day delay concession for groundwater users recognises that the storage capacity of the aquifer provides some short-term temporal buffer to impacts on river base flows.
Cockburn Review • Water users recommended a review of the current water sharing plan rules • Review commenced in 2015: • providing evidence to support the view that the Cockburn River alluvium and surface water of the Cockburn River are highly connected . • demonstrating the potential impacts of continued groundwater pumping on surface water flows in the Cockburn River at times when surface water access has ceased. • investigating possible alternative to the Kootingal Bridge river gauge as the cease to pump reference point that may provide a more appropriate groundwater cease to pump reference point. • review of the socio-economic impacts of the current water sharing plan cease to pump rules.
Cockburn Review • Outcome of the review found: • a highly connected surface water- groundwater system. • groundwater extraction has potential to impact on river flows and pool volumes • Eel-tailed catfish and Murray Cod inhabit these pools • current cease to pump reference point was unsuitable for the sustained low flow accuracy required by the WSP cease to pump rules • current WSP condition of visible flow at a rock bar 700m upstream of the Peel River and Cockburn River confluence was not implemented. • recommended relocating current orifice to 50m downstream of its current location. • initial socio-economic assessment was fit for purpose, however acknowledged the impacts on conjunctive (both surface and groundwater entitlement) users and those producing high value crops such as maize would differ from the regional estimates.
Surface water – groundwater interaction Source: Connected Water, Commonwealth Government
Surface water – groundwater interaction Evidence of connectivity: • Flow duration curve – river flows 85% of the time at Kootingal Bridge • River and groundwater hydrographs – close to identical amplitude and timing of responses • River losses in the upper catchment during dry periods • Temperature and chemistry studies – large groundwater exchange compared with river flow volumes
Water Level (m AHD) 409 410 411 412 413 414 415 GW093036 Jan-00 Dec-00 Dec-01 Dec-02 GW093037 Jan-04 Dec-04 Dec-05 Dec-06 GW093038 Jan-08 Dec-08 Date Dec-09 Dec-10 GW093039 Jan-12 Dec-12 Dec-13 GW093040 Dec-14 Jan-16 Dec-16 Dec-17 419099 Dec-18 Jan-20
Mechanisms for impact: 1. Reduction in baseflow 2. Increase in losses 3. Reversal of baseflow to losses The magnitude and timing of impacts variable according to: 1. Total extracted volume 2. Rates of extraction 3. Distance of bore from river Source: Connected Water, Commonwealth Government
Quantifying Impacts in Cockburn Zone – Analytical Model • 2013-14 water year – dry year chosen as that is when the impacts matter • 11 highest-use bores only modelled (67% of all use) – others ignored • 3 Town Water Supply bores – pump all year • 8 irrigation bores – commence use 1 December • Pump for a further 100 days
600 500 Total Cumulative Loss ML 400 300 200 100 0 0 10 20 30 40 50 60 70 80 90 100 Days Total Cumulative Loss ML Cumulative Loss ML at days 0, 14, 28, 50, 75 and 100
Importance of maintaining pools • The intent of the WSP groundwater access rules is to protect the pools in the river during dry seasons to provide habitat for identified fish. • A known population of the Eel-tailed Catfish and Murray Cod inhabit the Cockburn River. • Eel-tailed Catfish is listed as an Endangered Population in the Fisheries Management Act 1994. • Murray Cod is listed as part of the Aquatic Ecological Community in the Natural Drainage System of the Lower Murray River Catchment in the Fisheries Management Act 1994. • The NSW government required under MDBA Basin Plan to develop strategies for managing or addressing risks to the condition or continued availability, of water resources, which could affect the Eel-tailed Catfish and Murray Cod population.
Native fish distribution within the Cockburn River Water Source
Proposed changes to the water sharing plan • The NSW Department of Industry – Water proposes amending the existing cease to pump threshold: • Current rule - after the flow level of the Cockburn River at Kootingal gauge has been equal to or lower than 0.25 metres for 28 consecutive days, to • Amended rule- after the flow level of the Cockburn River at a flow monitoring site 50 m downstream of Kootingal bridge gauge has been equal to, or lower than, 0.3 ML/day for 28 consecutive days, in the access rules for the Cockburn River Alluvium Management Zone. • additional orifice (linked to the existing gauge) to a more stable location, further 50 m downstream of the existing site. This reflects the amendments proposed for the Cockburn River Water Source. All other aspects of the access rule would remain the same.
Proposed relocation of the Kootingal gauge
Questions?
Have your say • Water Resource Plan Public Exhibition period till 20 July 2019. • Feedback being sought from the public and water users. • Online submission process on Department of Industry website: www.industry.nsw.gov.au/water/plans-programs/water-resource-plans/drafts/namoi- alluvium • By email: namoi.gw.wrp@dpi.nsw.gov.au
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