Ashley-Waimakariri
groundwater resources
i
investigation
ti ti
Introductions
• Matt Dodson, Hydrogeologist
– Area groundwater scientist for the
Waimakariri CWMS zone
• Philippa Aitchison-Earl, Groundwater
y
g
hydrologist
• Lisa Scott, Groundwater Quality
Scientist
• John Weeber and Phil Abraham
P
Presentation
t ti outline
tli
•Terminology
e
o ogy
•Purpose of the study
•Background
•Conceptual
Conceptual model
•Surface /Groundwater interactions
•Water balance
•Future
Future work
•Questions
Terminology (handout)
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Aquifer – Geological formation/s producing useful quantities of water.
Confining layer – Relatively low-permeability layer that bounds a
aquifer.
Confined aquifer – Aquifer overlaid by a confining layer.
Artesian aquifer – An artesian aquifer is a confined aquifer containing
groundwater under positive pressure.
Recharge – A hydrologic process where water moves to groundwater.
Land surface recharge (LSR) – Water that infiltrates through the soil
zone to recharge groundwater (rainfall or irrigation return water).
Discharge – Groundwater that discharges out of the study area or to
the surface.
surface
Seawater intrusion – Seawater than migrates landwards.
Stream depletion – The effect of groundwater abstraction on surface
waterways.
Gauging – Measurement of a river/stream flow rate at a point.
Water balance
• Water balance equation can be used to
describe the flow of water in and out of
y
a system.
• Groundwater storage = Inputs (i.e.
Recharge) – Outputs (i
(i.e.
e Discharge)
Discharge).
Surface/ groundwater interactions
The purpose of the study
• Investigate surface and groundwater
interaction
• Calculate a regional water balance
-------------------------------------------------------• Eyre groundwater allocation zone (GAZ
or GWAZ)
Background
From Smith 2012
Background
• Project planning began in mid 2009.
• Integrated approach (Surface and
groundwater teams).
• Field work commenced in July 2009
((two yyear field p
programme).
g
)
CONCEPTUAL MODEL
A hl – Waimakariri
Ashley
W i k i i plains
l i
Rainfall recharge
Irrigation induced recharge
Race losses
Eyre & Cust River recharge
Waimakariri River recharge
Ashley River/Rakahuri recharge
Abstraction
Spring
p g discharge
g
Offshore discharge
Adapted from Sanders 1997
Surface/ groundwater interactions
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Spring locations
Piezometric survey
Waimakariri River
Eyre River
Cust River
Ashley River/Rakahuri
Lowland streams
-2.8 m3/s
-2.7 m3/s
3
-5.6 m3/s +0.1 m3/s +1.4 m /s
-0.6 m3/s
M36/5436 GWL and Waimakariri flow
1400
66401 Waimakariri River at Old Highway
Bridge
g ((Recorder))
M35/5436
Sample date 10/10/11
1000
Flow
w (m 3/s)
-0.5
Chemistry and isotope results indicate
Waimakariri River recharge and LSR
-1
800
600
-1.5
400
-2
200
0
1-Apr-09
-2.5
10-Jul-09
18-Oct-09
26-Jan-10
6-May-10
Date
14-Aug-10 22-Nov-10
2-Mar-11
GWL
L (mbgl)
1200
0
Typically flows
only 1-2/ yr
Water balance
• Recharge sources
– Rainfall recharge
– Irrigation induced recharge
– River recharge
– Race
R
llosses ((stockwater
t k t and
d WIL)
Water balance
• Discharge sources
– Spring discharge
– Abstraction
– Offshore discharge (cannot measure)
• Interzone flow
Recharge
Discharge
LSR
360 7 M m3/ year
360.7
Spring discharge
222 7 M m3/ year
222.7
Surface water losses
120.5 M m3/ year
Abstraction
52.1 M m3/ year
Race losses
53.3 M m3/ year
TOTAL
534.5 M m3/ year
TOTAL
274.8 M m3/ year
Offshore flow
<259.7 M m3/ year
AshleyWaimakariri
plains
Recharge
Discharge
LSR
21 5 M m3/ year
21.5
Spring discharge
76 3 M m3/ year
76.3
Ashley River/
Rakahuri
46.7 M m3/ year
Abstraction
6.9 M m3/ year
R
Race
llosses
4 6 M m3/ year
4.6
TOTAL
72.8 M m3/ year
TOTAL
83.2 M m3/ year
Interzone flow
>10.4 M m3/ year
(inflow – Cust)
Ashley
GAZ
Recharge
Discharge
LSR
86 0 M m3/ year
86.0
Spring discharge
50 8 M m3/ year
50.8
Cust River
7.8 M m3/ year
Abstraction
8.1 M m3/ year
Race losses
13.6 M m3/ year
TOTAL
107.5 M m3/ year
TOTAL
58.9 M m3/ year
Interzone flow
<48.5 M m3/ year
(outflow – Ashley)
Cust
GAZ
Recharge
Discharge
LSR
253 2 M m3/ year
253.2
Spring discharge
95 6 M m3/ year
95.6
Eyre & Waimakariri
River
65.9 M m3/ year
Abstraction
37.1 M m3/ year
R
Race
llosses
35 0 M m3/ year
35.0
TOTAL
354.2 M m3/ year
TOTAL
132.6 M m3/ year
Interzone flow
<221.6 M m3/ year
(Outflow – Cust)
Eyre
GAZ
Eyre GAZ allocation limit
• An adaptation of a method in the NRRP
we have calculated a allocation limit for
y zone,, being;
g;
the Eyre
– Proposed limit 99.1 M m3/year (50% rainfall
recharge)
– Current limit 81.3 M m3/year
CONCEPTUAL MODEL
A hl – Waimakariri
Ashley
W i k i i plains
l i
Adapted from Sanders 1997
Work currently underway or due to
start soon
• Permitted takes
• Spring mapping – Upper Cust River
• Age determination – springs
Proposed work for discussion
• Lower Waimakariri River recharge
– Sampling springs near the Waimakariri
River bank
– Sample at different
Proposed work for discussion
• Eyrewell forest – monitoring
– Information gap
Proposed work for discussion
• Determine losses from the Ashley
River/Rakahuri in the upper reaches
– Recharge source to the Cust GAZ?
Proposed work for discussion
• Ohoka Stream recorder
– Springs recharged from up-gradient LSR
Proposed work for discussion
• Metering of takes
Proposed work for discussion
• GW Model
– Better constraint water balance
– Determine flow paths to evaluate the
current allocation boundaries
– Can be used to predict effects of
groundwater abstraction on the surface
water flows
– Assist with nutrient management and
n trient allocation limit setting
nutrient
Questions