managing the groundwater resources of the earnscleugh terrace aquifer
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Managing the groundwater resources of the Earnscleugh Terrace Aquifer OTAGO REGIONAL COUNCIL WORKSHOP – 18 March. Welcome / overview Policy presentation: aim, key concepts, process Science presentation: aquifer hydrology Q & A session Small group session - PowerPoint PPT PresentationTRANSCRIPT
Managing the groundwater resources
of the Earnscleugh Terrace Aquifer
OTAGO REGIONAL COUNCIL WORKSHOP – 18 March
Welcome / overview Policy presentation: aim, key concepts, process Science presentation: aquifer hydrology Q & A session Small group session Conclusion / Where to from here Tea & coffee
Today
Setting a
maximum allocation volume & aquifer restriction levels
for the Earnscleugh terrace aquifer
in the Water Plan
Project aim
Total volume of groundwater that may be taken from an aquifer by resource consents.
Measured in m3/year. To avoid aquifer depletion/compaction and
groundwater contamination, ensure surface water outflows.
Further allocation is available if combined consented takes < MAV
What is a maximum allocation volume?
Set in Schedule 4A of the Water Plan - takes into account hydrology, environmental, social economic, cultural, considerations
OR
Set as 50% mean annual recharge (interim/default MAV)
How is the maximum allocation volume determined?
Permitted vs. consented takes
Existing consents vs. applications for new takes
Groundwater takes not allocated as primary allocation (surface water)
Does the maximum allocation volume affect me?
Aquifer levels at which restrictions apply to groundwater takes
Takes usually restricted by 25%, 50% or 100% To maintain groundwater levels in localised
areas of high demand or during droughts No default set in the Water Plan Determined based on local environmental,
socio/economic, cultural considerations
What are aquifer restriction levels?
Consented takes
Community water supplies (Schedule 3B)
Permitted takes under Rule 12.2.2.2
When does an aquifer restriction level affect me?
RMA process
Workshop #2 (Optional)Discuss suggested management option
Workshop #1 (Today)Explain Water Plan basicsDiscuss science – technical recommendationListen community aspirations and values
Changes put into effect
Consultation process
Consultation key
stakeholders, incl. Iwi
Notify proposed plan change
Consultation draft
EarnscleughTerrace AquiferSimon East, Groundwater Scientist
Earnscleugh Terrace Aquifer boundary
Earnscleugh Terrace
Geology map
Earnscleugh Terrace cross section
Groundwater contours
Groundwater wells and take permits
Consumptive takes• 8 takes• Assessed maximum annual
take of 1.01 Mm3
• Actual use may be as low as 30%
Partially consumptive takes• 2 takes• Assessed maximum annual
take of 31.8 Mm3
• Possibly as much as 75% of water returned to the aquifer
• Actual use may be as low as 50%
Non-consumptive takes
Earnscleugh gold mine
Earnscleugh gold mine
Monitoring well locations
G42/0119 groundwater level monitoring
1994 1999 2004 2009 2014
-25
-24
-23
-22
-21
-20
Dept
h to
wat
er (m
)
G42/0190 groundwater level monitoring
1994 1999 2004 2009 2014
-12
-11
-10
-9
-8
-7
Dept
h to
wat
er (m
)
Why are groundwater levels declining?
• Increased groundwater pumping?
• Less rainfall?• Lower surface water flows?• Changes to irrigation?
Rainfall trend and groundwater level
1994 1999 2004 2009 2014
-11
-10
-9
-8
-7
-250
-200
-150
-100
-50
0
50
100
150
200
250
Groundwater level
Rainfall trend
Dept
h to
wat
er (m
)
Rain
fall
trend
Recharge and discharge
Water balance component Recharge(Mm3/year)
Discharge(Mm3/year)
Rainfall recharge 0.35Fraser Irrigation Scheme excess 0.55
Losses from the upper Fraser River 24.60Water race losses 3.40
Losses from Omeo Creek ?Range front recharge ?
Losses from the Clutha River ?Drainage into the lower Fraser River 16.20
Groundwater pumping 0.15Drainage into the Clutha River from springs 4.00
Direct drainage into the Clutha River 8.5Totals 28.9 28.9
Water balance
Surface water interaction
Losing river
Gaining river
Maximum allocation volume (MAV)• Policy 6.4.10A sets the default MAV as 50% of the
mean annual recharge (MAR)• Water race leakage not included as it is only a
temporary source of recharge• Range front, Omeo Creek and Clutha River
recharge not included at this stage as they haven’t been fully assessed
Source Volume (Mm3/year)Rainfall recharge 0.35
Fraser Irrigation Scheme excess 0.55Losses from the upper Fraser River 24.60
Total MAR 25.00
MAV (50% of MAR) 12.75
Current allocation
Consumptive takes1.01 Mm3/year
Partially consumptive takes31.82 Mm3/year
Default MAV12.75 Mm3/year
Estimated assessed maximum allocation32.83 Mm3/year
Available allocation0.00 Mm3/year
Options for management
• Accept the default MAV (50% of MAR)
• Develop a tailored MAV:• Consider a higher MAV by undertaking further
investigations to determine additional recharge components
• Consider a lower MAV based on the maximum likely irrigation requirement for the zone or for the protection of other values
• Consider a groundwater restriction level to provide protection from groundwater level decline
Community input into the allocation process
Community involvement in identifying values and aspirations is an integral part of the process of setting allocation limits.
Combined with the science input, community involvement helps to achieve the best outcome.
Small Group Discussions
How do you use water from the aquifer?Have low groundwater levels ever affected you?
How often does this happen? How were you affected?What is important about the aquifer?
To you personally. For the local economy, environment, and community (social/cultural importance).
How would you like to see water from the aquifer being used in the future?
Are there any future growth opportunities? Are there any risks to this growth happening?
Small Group Discussions
Report Back
Further Feedback• Provide any further feedback by 1 April 2014
• Email: [email protected]
• Post: 70 Stafford Street, Private Bag 1954, Dunedin
• Phone: 0800 474 082
• Workshop materials, feedback forms will be put on the
website: www.orc.govt.nz