❓ Question on Notice regarding the management of groundwater extraction around Lake Mariginiup to improve its ecological condition, focusing on compliance with the Gnangara groundwater areas allocation plan and the impact of private bores.
AnsweredQoN 2998Legislative Council
QuestionView source ↗
I refer to the Department of Water’s Perth shallow groundwater investigation Lake Mariginiup, Hydrogeological record series report No. HG 36 of June 2010, and the finding that to improve the ecological condition of Lake Mariginiup, water levels must increase, and ask -
(1) Have private groundwater extractors in the region of Lake Mariginiup been advised, that in line with the recommendations of this report and of the Gnangara groundwater areas allocation plan, that their groundwater extraction licenses will be reduced by 20 percent?
(2) If no to (1), when will the Department of Water advise licensed groundwater extractors, and when will licenses be altered to reflect the report’s recommendations?
(3) When will all licenses within the groundwater management sub areas directly relevant to this report, and subject to the Gnangara groundwater areas allocation plan, be fully compliant with the recommendations?
(4) Precisely how many licenses, and for what volumes of water within the groundwater management sub-areas, are subject to these recommendations?
(5) Are these licenses each and severally subject to metering, monitoring and license compliance measures?
(6) If no to metering, monitoring and / or license compliance measures, why not?
(7) How many unlicensed bores are located within the groundwater management sub areas directly relevant to this report, and what volumes of water are estimated to be extracted by private unlicensed bores located within the groundwater management sub areas, directly relevant to this report?
(8) What appropriate hydrochemical triggers and management actions, will be developed to improve the ecological condition of Lake Mariginiup, and what timeline is in place to implement, action and review?
(9) What hydrochemical sampling and analysis program will be undertaken, and what timeline is in place to implement, action and review?
(10) How has Lake Mariginiup been managed to comply with Ministerial environmental criteria over the past decade?
(11) What are the hydrochemical implications for Lake Mariginiup from continued over-extraction, and drier climate scenarios?
(1) Have private groundwater extractors in the region of Lake Mariginiup been advised, that in line with the recommendations of this report and of the Gnangara groundwater areas allocation plan, that their groundwater extraction licenses will be reduced by 20 percent?
(2) If no to (1), when will the Department of Water advise licensed groundwater extractors, and when will licenses be altered to reflect the report’s recommendations?
(3) When will all licenses within the groundwater management sub areas directly relevant to this report, and subject to the Gnangara groundwater areas allocation plan, be fully compliant with the recommendations?
(4) Precisely how many licenses, and for what volumes of water within the groundwater management sub-areas, are subject to these recommendations?
(5) Are these licenses each and severally subject to metering, monitoring and license compliance measures?
(6) If no to metering, monitoring and / or license compliance measures, why not?
(7) How many unlicensed bores are located within the groundwater management sub areas directly relevant to this report, and what volumes of water are estimated to be extracted by private unlicensed bores located within the groundwater management sub areas, directly relevant to this report?
(8) What appropriate hydrochemical triggers and management actions, will be developed to improve the ecological condition of Lake Mariginiup, and what timeline is in place to implement, action and review?
(9) What hydrochemical sampling and analysis program will be undertaken, and what timeline is in place to implement, action and review?
(10) How has Lake Mariginiup been managed to comply with Ministerial environmental criteria over the past decade?
(11) What are the hydrochemical implications for Lake Mariginiup from continued over-extraction, and drier climate scenarios?
AnswerView source ↗
Answered
25 November 2010
Responded by
Parliamentary Secretary representing the Minister for Water
Response time
16 days
This 11 part question required a considerable amount of departmental resources to answer.
(1) Yes.
(2) Not applicable
(3) The Department of Water (DoW) is not imposing an across the board reduction in water entitlements for all licensees. As opportunities arise, where users are not using all of their entitlement or where water users are not taking water according to the licence, recouping of water is occurring. Accordingly it is not possible to give an exact timeframe.
(4) The DoW's report Gnangara groundwater areas allocation plan details licence statistics, including total licensee numbers and groundwater entitlements. This report is found on the DoW's website: www.water.wa.gov.au
(5) Yes - all licences are subject to one or all.
(6) Not applicable
(7) The DoW estimates there are approximately 50 unlicensed bores in the Mariginiup subarea that are exempt from licensing. The estimated unlicensed garden bore use is 0.02GL/yr.
(8) Hydrochemical triggers and management actions will be reported in the next review of the Gnangara groundwater areas allocation plan scheduled for 2012. Hydrochemical triggers are likely to include factors of pH, metals and nutrients. Management actions are likely to include aspects of pine thinning/harvesting and the use of water sensitive urban design as the area is urbanised. These two management actions are expected to result in rising water levels and will contribute to improved ecological conditions in Lake Mariginiup. Other management actions include more local area computer modelling and the continued recoup of water as detailed in 3.
(9) A hydrochemical sampling and analysis program will be developed for the 2012 review of the Gnangara groundwater areas allocation plan. Parameters are likely to include:
· Quarterly hydrochemical sampling of major ions, metals, nutrients at four sites
· Monthly hydrochemical sampling of the lake when surface water is present.
The program will be implemented following the review of the plan in 2012.
(10) The DoW's policy on groundwater abstraction in the vicinity of sensitive wetland areas (e.g Lake Mariginiup) on the Gnangara Mound is:
"The Department of Water will not approve proposals to change the location of groundwater abstraction to take additional groundwater from the Gnangara Mound (Superficial Aquifer), in circumstances that may add to water level decline in Groundwater Dependent Ecosystems."
(11) It is expected that water level recovery in Lake Mariginiup will be aided through the continued reductions in private groundwater abstraction over the Gnangara Mound and with land-use changes. However, this will take a number of years. Any further dry periods may result in exposure of acid sulphate soils with a corresponding decline in pH and increased metal concentrations in the lake.
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(1) Yes.
(2) Not applicable
(3) The Department of Water (DoW) is not imposing an across the board reduction in water entitlements for all licensees. As opportunities arise, where users are not using all of their entitlement or where water users are not taking water according to the licence, recouping of water is occurring. Accordingly it is not possible to give an exact timeframe.
(4) The DoW's report Gnangara groundwater areas allocation plan details licence statistics, including total licensee numbers and groundwater entitlements. This report is found on the DoW's website: www.water.wa.gov.au
(5) Yes - all licences are subject to one or all.
(6) Not applicable
(7) The DoW estimates there are approximately 50 unlicensed bores in the Mariginiup subarea that are exempt from licensing. The estimated unlicensed garden bore use is 0.02GL/yr.
(8) Hydrochemical triggers and management actions will be reported in the next review of the Gnangara groundwater areas allocation plan scheduled for 2012. Hydrochemical triggers are likely to include factors of pH, metals and nutrients. Management actions are likely to include aspects of pine thinning/harvesting and the use of water sensitive urban design as the area is urbanised. These two management actions are expected to result in rising water levels and will contribute to improved ecological conditions in Lake Mariginiup. Other management actions include more local area computer modelling and the continued recoup of water as detailed in 3.
(9) A hydrochemical sampling and analysis program will be developed for the 2012 review of the Gnangara groundwater areas allocation plan. Parameters are likely to include:
· Quarterly hydrochemical sampling of major ions, metals, nutrients at four sites
· Monthly hydrochemical sampling of the lake when surface water is present.
The program will be implemented following the review of the plan in 2012.
(10) The DoW's policy on groundwater abstraction in the vicinity of sensitive wetland areas (e.g Lake Mariginiup) on the Gnangara Mound is:
"The Department of Water will not approve proposals to change the location of groundwater abstraction to take additional groundwater from the Gnangara Mound (Superficial Aquifer), in circumstances that may add to water level decline in Groundwater Dependent Ecosystems."
(11) It is expected that water level recovery in Lake Mariginiup will be aided through the continued reductions in private groundwater abstraction over the Gnangara Mound and with land-use changes. However, this will take a number of years. Any further dry periods may result in exposure of acid sulphate soils with a corresponding decline in pH and increased metal concentrations in the lake.
Notice: This document is created or edited using unregistered or evaluation copy of rtLib valid for testing or development purposes only. To use it for productive or any other purposes please register it. You may purchase the license on
http://www.rtlib.com
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