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Parliamentary Questions


Question On Notice No. 1389 asked in the Legislative Council on 12 June 2018 by Hon Diane Evers

Question Directed to the: Minister for Regional Development representing the Minister for Water
Parliament: 40 Session: 1


Question

(1) In which year will Perth's next desalination plant be needed given current population growth and climate trends:
(a) in relation to (1), what is the next desalination plant's planned annual water production; and
(b) in relation to (1), what is the estimated production cost of water from Perth's next seawater desalination plant in dollars per kilolitre?
(2) Is the Water Corporation contemplating other sources of potable water in addition to Perth's next seawater desalination plant:
(a) if yes to (2), what are they, how much water will each one produce, and at what estimated cost per kilolitre?
(3) Has desalinated water been stored in the Wellington dam in recent years to be used at a later time:
(a) if yes to (3), is that water now too saline to be used for human consumption?
(4) Is the Water Corporation contemplating new water use reduction measures in addition to those already in place:
(a) if yes to (4), what are they, how much water will they each save and at what estimated cost per kilolitre?
(5) What are the current production costs of water from each of the following sources in the Integrated Water Supply Scheme (IWSS):
(a) shallow groundwater;
(b) sources of deep groundwater:
(i) Leederville Aquifer; and
(ii) Yaragadee Aquifer; and
(c) existing reservoirs in aggregate including Harvey Irrigation water savings, Perth and southern Seawater desalination plants and the Beenyup Groundwater Replenishment Scheme?
(6) How much water, in gigalitres per year, is produced from each of the above sources in a 'normal' water year?
(7) Is the Water Corporation planning to maintain, expand or reduce the annual volume of groundwater it harvests from the Gnangara Mound given falling groundwater pressures and levels in its major aquifers:
(a) if yes to (7), at what rate of change, and for how long?
(8) How much revenue does the Water Corporation collect in Metropolitan drainage rates:
(a) how much of that revenue is applied to drainage-related matters?

Answered on 21 August 2018

(1) Water Corporation responds and adapts to changing circumstances, including climate change, by identifying and investigating the requirement for new sources.  While desalination is likely to be the next source for Perth, this is not yet a certainty.  Assuming current demand reduction targets, maximising current desalination production and a minimum of 25 gigalitres (GL)/annum runoff into the dams, the next source will not be needed within the next five years.
(a) It is likely that at least 50GL/annum from new source/s will be required.
(b) Planning is still at a conceptual stage and early estimates should be treated with caution due to many unknown factors including site location, plant configuration and scheme integration.  Total cost for a future seawater desalination plant running at capacity is generally estimated to be in the range of $3.00-$4.00/kL (including capital and operating costs).

(2) The Water Corporation continues to investigate other options such as groundwater replenishment at the Subiaco and Woodman Point Wastewater Treatment Plants.
(a) Groundwater replenishment can be developed in 10-20 GL increments, with total combined source capacity of approximately 60-70 GL/yr. Early planning estimates indicate the total cost for these sources to be in the range of $2.00 to $4.00/kL (including capital and operating costs). These sources require significant investigation to understand local groundwater conditions and concept development to confirm cost estimates.

(3) No.
(a) Not applicable.

(4) Continued efforts to reduce demand remain a priority for the Water Corporation.
(a) To support the community in continuing to reduce water use, the Water Corporation is undertaking a new Perth Residential Water Use Study.  This will identify changes in household water use trends since the previous study was completed ten years ago. The study is scheduled to be completed in 12 to 18 months, with interim findings informing future targeted water use efficiency programs, the costs of which are yet to be determined.

(5)(a)-(b)(i)(ii)
Groundwater abstracted from all three aquifers is collected and treated through the same pipes and treatment plants, making it extremely difficult to determine production costs from each aquifer.
Based on operating costs from 2016/17, groundwater productions costs are approximately $0.40/kL

(c) Based on the date the question has been asked, 2016/2017 operating costs are provided as they need be amortised over a full financial year:
• Harvey irrigation water savings are not applicable as water was not sourced from Harvey Water assets for public water supplies.
• Surface water (including Mundaring) production costs approximately $0.45/kL.
• Perth Seawater Desalination Plant production costs approximately $0.90/kL.
• Southern Seawater Desalination Plant production costs approximately $1.35/kL
• The Beenyup Groundwater Replenishment Scheme was not operating in 2016/2017 so actual figures are not able to be provided at this stage.

(6) In 2017/18, production was planned as follows:
• Groundwater licenced:
 o Shallow groundwater: 39 GL
 o Leederville aquifer groundwater: 48 GL
 o Yarragadee aquifer groundwater: 54 GL
 o Groundwater replenishment - approximately 7 GL recharged in 2017/18 (equivalent abstraction included in above planned groundwater figures.)
• Southern Seawater Desalination Plant – 103 GL
• Perth Seawater Desalination Plant – 46 GL
• Harvey Irrigation water savings - not applicable.

(7) The Water Corporation plans to maintain its levels of abstraction from the Gnangara Mound in 2018/19.
(a) The Water Corporation is required to submit an annual Groundwater Extraction Plan as part of its Licence to abstract groundwater. The Licence is granted by the Department of Water and Environmental Regulation in accordance with the Gnangara Allocation Plan. The Department is currently reviewing the Plan, including the allocation limits. Any changes to the Corporation’s future groundwater allocation will be the direct outcome of this process.

(8) $55.7 million in 2017/18
(a) $49.8 million in 2017/18