❓ Question on Notice regarding water extraction from the Gnangara Mound for the Integrated Water Supply Scheme (IWSS) between 1989-2010, focusing on superficial and confined aquifers, environmentally sensitive areas, urban areas, drain interception, and government reduction strategies.
AnsweredQoN 2681Legislative Council
QuestionView source ↗
I refer to the Integrated Water Supply Scheme (IWSS) extraction from Gnangara Mound, and ask -
(1) How much water was extracted for the IWSS from the superficial aquifer of the Gnangara Mound, for each year from 1989-90 to 2009-10?
(2) How much water was extracted for the IWSS, from the superficial aquifer in environmentally sensitive areas of the Gnangara Mound, for each year from 1989-90 to 2009-10?
(3) How much water was extracted for the IWSS, from the superficial aquifer in urban areas of the Gnangara Mound, for each year from 1989-90 to 2009-10?
(4) How much water was extracted for the IWSS, from confined aquifers of the Gnangara Mound, for each year from 1989-90 to 2009-10?
(5) How much superficial groundwater is intercepted by drains across the Gnangara Mound?
(6) Why is this intercepted groundwater not being infiltrated back to the superficial groundwater aquifer?
(7) In line with the recommendations of the year old draft Gnangara Sustainability Strategy, how is the Government seeking to reduce overall extraction from the Gnangara Mound, to below 110 gigalitres from existing infrastructure each year?
(1) How much water was extracted for the IWSS from the superficial aquifer of the Gnangara Mound, for each year from 1989-90 to 2009-10?
(2) How much water was extracted for the IWSS, from the superficial aquifer in environmentally sensitive areas of the Gnangara Mound, for each year from 1989-90 to 2009-10?
(3) How much water was extracted for the IWSS, from the superficial aquifer in urban areas of the Gnangara Mound, for each year from 1989-90 to 2009-10?
(4) How much water was extracted for the IWSS, from confined aquifers of the Gnangara Mound, for each year from 1989-90 to 2009-10?
(5) How much superficial groundwater is intercepted by drains across the Gnangara Mound?
(6) Why is this intercepted groundwater not being infiltrated back to the superficial groundwater aquifer?
(7) In line with the recommendations of the year old draft Gnangara Sustainability Strategy, how is the Government seeking to reduce overall extraction from the Gnangara Mound, to below 110 gigalitres from existing infrastructure each year?
AnswerView source ↗
Answered
22 September 2010
Responded by
Parliamentary Secretary representing the Minister for Water
Response time
36 days
(1) The Department of Water (DoW) has collated the following information on the amount of groundwater abstracted by the IWSS from the superficial aquifer on the Gnangara Mound for each year from 1989-90 to 2009-10:
· 1989: 31.75 Gigalitres per year (GL/yr)
· 1990: 33.90 GL/yr
· 1991: 37.13 GL/yr
· 1992: 35.73 GL/yr
· 1993: 34.89 GL/yr
· 1994: 36.85 GL/yr
· 1995: 35.50 GL/yr
· 1996/97: 35.63 GL/yr
· 1997/98: 36.53 GL/yr
· 1998/99: 40.64 GL/yr
· 1999/00: 41.65 GL/yr
· 2000/01: 47.15 GL/yr
· 2001/02: 58.22 GL/yr
· 2002/03: 57.88 GL/yr
· 2003/04: 54.03 GL/yr
· 2004/05: 52.87 GL/yr
· 2005/06: 45.85 GL/yr
· 2006/07: 60.16 GL/yr
· 2007/08: 46.26 GL/yr
· 2008/09: 44.48 GL/yr
· 2009/10: 32.06 GL/yr
(2) The DoW's Gnangara groundwater areas allocation plan, released in November 2009, provides strategies to protect groundwater-dependant ecosystems due to declining groundwater levels on the Gnangara Mound by limiting, or restricting the abstraction of groundwater in environmentally sensitive areas. The Water Corporation (Corporation) manages the IWSS. The DoW manages the abstraction of water for the IWSS through the Corporation's licence conditions. A key component for managing IWSS abstractions is the setting of environmental sensitivity classifications for each superficial aquifer production bore on the Gnangara Mound. These classifications assign each bore with either a sensitivity 1, 2 or 3 classifications. Sensitivity 1 bores are those located close to environmentally sensitive areas and following annual review by the DoW, are capped to only pump a specified amount for the forthcoming water year. Sensitivity 2 bores are those located in less environmentally sensitive areas, while sensitivity 3 bores have minimal environmental constraints. The following data is the combined yearly amount of groundwater abstracted from sensitivity 1 IWSS bores on the Gnangara Mound:
· 1989/1990: 12.21 GL/yr
· 1990/1991: 11.79 GL/yr
· 1991/1992: 7.75 GL/yr
· 1992/1993: 10.12 GL/yr
· 1993/1994: 11.32 GL/yr
· 1994/1995: 12.43 GL/yr
· 1995/1996: 10.81 GL/yr
· 1996/1997: 11.28 GL/yr
· 1997/1998: 9.90 GL/yr
· 1998/1999: 8.61 GL/yr
· 1999/2000: 7.91 GL/yr
· 2000/2001: 7.95 GL/yr
· 2001/2002: 5.66 GL/yr
· 2002/2003: 4.57 GL/yr
· 2003/2004: 3.96 GL/yr
· 2004/2005: 4.78 GL/yr
· 2005/2006: 3.99 GL/yr
· 2006/2007: 6.74 GL/yr
· 2007/2008: 2.64 GL/yr
· 2008/2009: 2.30 GL/yr
· 2009/2010: 0.77 GL/yr
(3) The DoW is unable to provide data on the amount of water abstracted for the IWSS from the superficial aquifer in areas zoned urban on the Gnangara Mound. The Corporation's reporting requirements to the DoW, under licence conditions, does not require reporting of how much groundwater is annually abstracted per aquifer, per area and differentiated between various land zoning categories (e.g. urban, semi-rural, rural, industrial). The IWSS combines water from a variety of sources and delivers it directly to a treatment facility before distributing to customers within the metropolitan area. Therefore, it is not possible for the DoW to provide data on how much groundwater is abstracted from the superficial aquifer specifically for urban use.
(4) The amount of groundwater abstracted by the Corporation for the IWSS from the confined aquifers (ie. Leederville and Yarragadee) and semi confined aquifer (ie. Mirrabooka) of the Gnangara Mound for each year from 1989-90 to 2009-10 were as follows:
· 1989: 42.38 GL/yr
· 1990: 40.50 GL/yr
· 1991: 40.33 GL/yr
· 1992: 41.48 GL/yr
· 1993: 39.64 GL/yr
· 1994: 36.91 GL/yr
· 1995: 46.66 GL/yr
· 1996/1997: 49.46 GL/yr
· 1997/1998: 60.24 GL/yr
· 1998/1999: 71.01 GL/yr
· 1999/2000: 85.21 GL/yr
· 2000/2001: 90.74 GL/yr
· 2001/2002: 89.28 GL/yr
· 2002/2003: 92.88 GL/yr
· 2003/2004: 96.33 GL/yr
· 2004/2005: 99.06 GL/yr
· 2005/2006: 91.19 GL/yr
· 2006/2007: 100.68 GL/yr
· 2007/2008: 89.46 GL/yr
· 2008/2009: 91.98 GL/yr
· 2009/2010: 78.0 GL/yr
(5) There is no data available on the quantum of superficial groundwater intercepted by constructed drains across the Gnangara Mound. Where measurement of flows in drains or natural streams occurs, it is not possible to accurately estimate the proportion of the total flow that is attributable to groundwater interception.
(6) The DoW's current policies for urban drainage management are designed to prevent or minimise interception of the superficial groundwater aquifer. Where this does occur the policy requires the intercepted water, where possible, to be re-infiltrated prior to reaching the ocean or river
(7) The goal of reducing extraction to below 110 GL/yr is for the IWSS only, from all aquifers, including the Gnangara Mound (superficial aquifer). The DoW revised the Variable Groundwater Abstraction Rule in the Gnangara groundwater areas allocation plan to meet an abstraction target of 120 GL/yr from the Gnangara (110 GL/yr) and Jandakot (10 GL/yr) systems by 2012.
The Corporation will increase water efficiency and conservation measures to reduce demand on the IWSS. The plan outlines the strategies that the Corporation will prepare and update as part of its licence conditions to abstract groundwater.
The DoW will review the allocation of groundwater for the IWSS from 2012 following commissioning of the Southern Seawater Desalination Plant. The review will be informed by the land and water use recommendations of the draft Gnangara Sustainability Strategy, including the recommendation that the long-term allocation for the IWSS be reduced from the current 145 GL/yr maximum to 110 GL/yr.
Overall, the DoW is reducing water use on the Gnangara Mound by:
· Reduced allocation limits
· Recouping unused entitlements
· Refusing licences in fully allocated areas
· Working with local government on water conservation plans
· Working with licensees to increase efficiencies in water use
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
· 1989: 31.75 Gigalitres per year (GL/yr)
· 1990: 33.90 GL/yr
· 1991: 37.13 GL/yr
· 1992: 35.73 GL/yr
· 1993: 34.89 GL/yr
· 1994: 36.85 GL/yr
· 1995: 35.50 GL/yr
· 1996/97: 35.63 GL/yr
· 1997/98: 36.53 GL/yr
· 1998/99: 40.64 GL/yr
· 1999/00: 41.65 GL/yr
· 2000/01: 47.15 GL/yr
· 2001/02: 58.22 GL/yr
· 2002/03: 57.88 GL/yr
· 2003/04: 54.03 GL/yr
· 2004/05: 52.87 GL/yr
· 2005/06: 45.85 GL/yr
· 2006/07: 60.16 GL/yr
· 2007/08: 46.26 GL/yr
· 2008/09: 44.48 GL/yr
· 2009/10: 32.06 GL/yr
(2) The DoW's Gnangara groundwater areas allocation plan, released in November 2009, provides strategies to protect groundwater-dependant ecosystems due to declining groundwater levels on the Gnangara Mound by limiting, or restricting the abstraction of groundwater in environmentally sensitive areas. The Water Corporation (Corporation) manages the IWSS. The DoW manages the abstraction of water for the IWSS through the Corporation's licence conditions. A key component for managing IWSS abstractions is the setting of environmental sensitivity classifications for each superficial aquifer production bore on the Gnangara Mound. These classifications assign each bore with either a sensitivity 1, 2 or 3 classifications. Sensitivity 1 bores are those located close to environmentally sensitive areas and following annual review by the DoW, are capped to only pump a specified amount for the forthcoming water year. Sensitivity 2 bores are those located in less environmentally sensitive areas, while sensitivity 3 bores have minimal environmental constraints. The following data is the combined yearly amount of groundwater abstracted from sensitivity 1 IWSS bores on the Gnangara Mound:
· 1989/1990: 12.21 GL/yr
· 1990/1991: 11.79 GL/yr
· 1991/1992: 7.75 GL/yr
· 1992/1993: 10.12 GL/yr
· 1993/1994: 11.32 GL/yr
· 1994/1995: 12.43 GL/yr
· 1995/1996: 10.81 GL/yr
· 1996/1997: 11.28 GL/yr
· 1997/1998: 9.90 GL/yr
· 1998/1999: 8.61 GL/yr
· 1999/2000: 7.91 GL/yr
· 2000/2001: 7.95 GL/yr
· 2001/2002: 5.66 GL/yr
· 2002/2003: 4.57 GL/yr
· 2003/2004: 3.96 GL/yr
· 2004/2005: 4.78 GL/yr
· 2005/2006: 3.99 GL/yr
· 2006/2007: 6.74 GL/yr
· 2007/2008: 2.64 GL/yr
· 2008/2009: 2.30 GL/yr
· 2009/2010: 0.77 GL/yr
(3) The DoW is unable to provide data on the amount of water abstracted for the IWSS from the superficial aquifer in areas zoned urban on the Gnangara Mound. The Corporation's reporting requirements to the DoW, under licence conditions, does not require reporting of how much groundwater is annually abstracted per aquifer, per area and differentiated between various land zoning categories (e.g. urban, semi-rural, rural, industrial). The IWSS combines water from a variety of sources and delivers it directly to a treatment facility before distributing to customers within the metropolitan area. Therefore, it is not possible for the DoW to provide data on how much groundwater is abstracted from the superficial aquifer specifically for urban use.
(4) The amount of groundwater abstracted by the Corporation for the IWSS from the confined aquifers (ie. Leederville and Yarragadee) and semi confined aquifer (ie. Mirrabooka) of the Gnangara Mound for each year from 1989-90 to 2009-10 were as follows:
· 1989: 42.38 GL/yr
· 1990: 40.50 GL/yr
· 1991: 40.33 GL/yr
· 1992: 41.48 GL/yr
· 1993: 39.64 GL/yr
· 1994: 36.91 GL/yr
· 1995: 46.66 GL/yr
· 1996/1997: 49.46 GL/yr
· 1997/1998: 60.24 GL/yr
· 1998/1999: 71.01 GL/yr
· 1999/2000: 85.21 GL/yr
· 2000/2001: 90.74 GL/yr
· 2001/2002: 89.28 GL/yr
· 2002/2003: 92.88 GL/yr
· 2003/2004: 96.33 GL/yr
· 2004/2005: 99.06 GL/yr
· 2005/2006: 91.19 GL/yr
· 2006/2007: 100.68 GL/yr
· 2007/2008: 89.46 GL/yr
· 2008/2009: 91.98 GL/yr
· 2009/2010: 78.0 GL/yr
(5) There is no data available on the quantum of superficial groundwater intercepted by constructed drains across the Gnangara Mound. Where measurement of flows in drains or natural streams occurs, it is not possible to accurately estimate the proportion of the total flow that is attributable to groundwater interception.
(6) The DoW's current policies for urban drainage management are designed to prevent or minimise interception of the superficial groundwater aquifer. Where this does occur the policy requires the intercepted water, where possible, to be re-infiltrated prior to reaching the ocean or river
(7) The goal of reducing extraction to below 110 GL/yr is for the IWSS only, from all aquifers, including the Gnangara Mound (superficial aquifer). The DoW revised the Variable Groundwater Abstraction Rule in the Gnangara groundwater areas allocation plan to meet an abstraction target of 120 GL/yr from the Gnangara (110 GL/yr) and Jandakot (10 GL/yr) systems by 2012.
The Corporation will increase water efficiency and conservation measures to reduce demand on the IWSS. The plan outlines the strategies that the Corporation will prepare and update as part of its licence conditions to abstract groundwater.
The DoW will review the allocation of groundwater for the IWSS from 2012 following commissioning of the Southern Seawater Desalination Plant. The review will be informed by the land and water use recommendations of the draft Gnangara Sustainability Strategy, including the recommendation that the long-term allocation for the IWSS be reduced from the current 145 GL/yr maximum to 110 GL/yr.
Overall, the DoW is reducing water use on the Gnangara Mound by:
· Reduced allocation limits
· Recouping unused entitlements
· Refusing licences in fully allocated areas
· Working with local government on water conservation plans
· Working with licensees to increase efficiencies in water use
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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