Supervisor Associate Professor Ryan Vogwill
Evaluation of water and solute (Cl-) balance for two contrasting wetlands in a semi-arid environment, Western Australia
SCHOOL OF EARTH AND ENVIRONMENT
Oct 2013
Nathan Senevirathne
The University of Western Australia
BMNDRC
The study area is part of Buntine-Marchagee Natural Diversity Recovery Catchment (BMNDRC)
Study area
Regional setting of project area
The University of Western Australia
W023
W024
Regional setting of project area
Study area sub-catchment(~ 600 ha = 0.02 % of BMNDRC)
W023
W024
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Remnant vegetation and landuse
Wheat Plantation Canola Plantation
Lupin Plantation Re-vegetated in 2013 Eucalyptus overstory
Salt – tolerant shrubs
~4%~90%
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The entire study area is a low relief region that lies over Archaean granitic rock of the Yilgarn Craton; ~340 mAHD on WEST and ~290 mAHD on EAST
The typical soil structure is comprised of fresh granitic bedrock grading upwards into saprock and saprolite which are overlain by lacustrine clays, palaeochannel silts, yellow earthy sands (Balgerbine Soil System)
(Anand & Paine 2002)
Basement rocks are exposed only at a small area near western margin and maximum depth is about 35 m
There is only one dyke appearing just outside of south-west margin (Geological Survey Western Australia by Baxter & Lipple 1985)
Geology & Topography• Drilling program carried out in mid 2012• LiDAR data• Geological survey of Western Australia by Baxter & Lipple 1985• The geology, physiography and soils of wheatbelt valleys by Commander et al. 2001• Regolith geology of the Yilgarn Craton, Western Australia: implications for exploration by Anand & Paine 2002
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Soil types, dykes and isolated outcrops of granite in the study area (Baxter & Lipple 1985)
Geology & Topography
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The gradient of slope in the study area
Geology & Topography
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A
BC
D
A B
C D
Digital elevation profiles of study area using LiDAR elevation data
Geology & Topography
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Groundwater monitoring network
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W023 W024
surface flow that could be generated by a heavy rainfall
Methodology Surface water catchment delineation
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Methodology Surface water catchment delineation
New Boundary
618 ha
589 ha
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Methodology Hydrogeochemistry
Water samples were collected from monitoring bores and several wetlands on 30 th April 2013. Electrical Conductivity (EC), Oxidation-Reduction Potential (ORP), pH, and temperature were measured at the field.
Ion chromatography using Dionex DX500 systems to determine the concentrations of major cations and anions
Na-Cl type
waters
Na-Cl type
waters
The University of Western Australia
Dominance of Cl-, Na+, SO42-, Mg2+ and HCO3
- in water samples
Methodology Hydrogeochemistry
Molar Cl/Br ratios vs. Cl- concentrations (mol/L) in water samples collected from groundwater and wetlands
The University of Western Australia
Distribution of Total Dissolved Solids (TDS) in study area
Methodology Hydrogeochemistry
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Surface water in-flow Surface water out-flow
Rainfall
Open water body ET
Bare soil ET
Superficial in-flow Superficial out-flow
Bedrock
Saprolitic
Aquifer
Saprolitic
discharge
Saprolitic
recharge
Methodology Conceptual model of wetland-scaled water balance
∆𝑆∆ 𝑡
=(𝑃+𝐺𝑊 𝑖𝑛+𝑆𝑊 𝑖𝑛 )− (𝐸𝑇+𝑆𝑊 𝑜𝑢𝑡+𝐺𝑊 𝑜𝑢𝑡 )=0
𝐺𝑊 𝑖𝑛
𝐺𝑊 𝑖𝑛
𝑆𝑊 𝑖𝑛𝑆𝑊 𝑜𝑢𝑡
𝑃
𝐺𝑊 𝑜𝑢𝑡
𝐺𝑊 𝑜𝑢𝑡
[𝑃 ∙𝑋𝑝+𝑆𝑊 𝑖𝑛 ∙𝑋 𝑠𝑤 .𝑖𝑛+𝐺𝑊 𝑖𝑛∙ 𝑋𝐺𝑊 ,𝑖𝑛 ]− [𝑆𝑊 𝑜𝑢𝑡 ∙𝑋 𝑆𝑊 ,𝑜𝑢𝑡+𝐺𝑊 𝑜𝑢𝑡 ∙ 𝑋𝐺𝑊 ,𝑜𝑢𝑡 ]=0
The University of Western Australia
Methodology Conceptualising groundwater flow
A
A’
B
B’
Transects of hydrogeological profiles marked on study area sub-catchment
The University of Western Australia
Methodology Conceptualising groundwater flow
The University of Western Australia
Methodology Conceptualising groundwater flow
The University of Western Australia
Methodology Conceptualising groundwater flow
Groundwater equipotential lines and flow in shallow aquifer
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Methodology Conceptualising groundwater flow
Groundwater equipotential lines and flow in the saprolitic aquifer
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Methodology Evapotranspiration
Open water body Evapotranspiration
𝐸𝑇=𝐸𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑜𝑛 𝑓𝑟𝑜𝑚𝑎𝑛𝑜𝑝𝑒𝑛𝑤𝑎𝑡𝑒𝑟 𝑏𝑜𝑑𝑦
𝐸𝑠𝑎𝑙𝑡=𝐸𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑜𝑛𝑟𝑎𝑡𝑒 h𝑤𝑖𝑡 h𝑡 𝑒𝑒𝑓𝑓𝑒𝑐𝑡 𝑜𝑓 𝑇𝐷𝑆𝑖𝑛𝑤𝑎𝑡𝑒𝑟 𝑏𝑜𝑑𝑦
𝐸𝑝𝑎𝑛=𝑃𝑎𝑛 𝐸𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑜𝑛
𝐸𝑝𝑎𝑛/𝐸𝑙𝑎𝑘𝑒=𝐸𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑜𝑛𝑐𝑜𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑡
𝐴=𝑆𝑢𝑟𝑓𝑎𝑐𝑒𝑎𝑟𝑒𝑎
Where
(Tweeda, Leblanca & Cartwright 2009)
(Marimuthua, Reynoldsa & Salle 2005; Allison 1974; Tweeda, Leblanca & Cartwright 2009)
0.7
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Methodology Evapotranspiration
Estimating bare soil evapotranspiration - Chen (1992)
Monthly bare soil ET with E1 (0.024 of Epan) and E2 (0.4 of Epan)
J an Feb Mar Apr May J un J ul Aug Sep Oct Nov Dec
Epa n 396.4 357.7 310.5 191.4 121.1 72.8 81.4 97.2 131.2 209.0 281.2 379.4
Mean number
of days of rain
≥1mm
2.0 1.8 2.2 1.5 5.0 6.2 7.5 6.4 5.1 2.6 2.0 1.7
E1 (mm/month) 8.3 7.5 6.4 4.1 2.0 1.0 1.0 1.4 2.1 4.2 5.8 8.1
E2 (mm/month) 20.5 18.4 17.6 7.7 15.6 12.0 15.7 16.1 17.8 14.0 15.0 16.6
mid Feb – beginning June (4 months)
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Methodology Surface water run-off
• Assumed that surface run-off within the immediate vicinity of W023 and W024
(Groen and Savenije 2006)
J an Feb Mar Apr May J un J ul Aug Sep Oct Nov Dec Annual
Monthly Interception
(Im ) - mm6.8 5.1 7.3 4.4 15.4 17.1 22.1 18.4 14.2 7.4 5.3 5.5 129.1
J an Feb Mar Apr May J un J ul Aug Sep Oct Nov Dec Annual
Surface run-off from
area of 1000 m2
(m3
)
4.5 1.2 4.0 1.3 5.3 3.5 6.0 4.5 3.0 1.7 0.9 2.6 38.6
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Methodology Surface water run-off
Possible flow patterns of surface water in-flow (generated using ArcGIS 10.1)
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A
B
D
C
H
E
F
G
W023
W024
Methodology Surface water run-off
A B
DC
H E FG
Elevation profiles across W023 and W024
The University of Western Australia
Methodology Surface water run-off
Estimation of surface area of water body
W etland
H ighes t
s urafce Area
(m2
)
H ighes t water
level (m)
Annual minimum
water level (m)
S urface area at
minimum depth
(m2
)
Average s urface
area (m2
)
W 023 7623.5 1.35 0.70 1475.9 4549.7
W 024 10584.0 0.64 0.00 0.0 5292.0
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Volume
(m3
/year)
Cl-
concentration
(mg/L )
Cl- M as s
(kg/year)Comments
P ercentage
of error
2188.7 8.0 17.5 S ection 3.1 and 3.12
1980.0 1036.0 2051.3 S ection 3.9 and 3.12
1048.9 1036.0 1086.7 S ection 3.9 and 3.12
4061.1 8.0 32.5 S ection 3.11 and 3.12
9278.7 3188.0 Total input
1440.0 1825.0 2628.0 S ection 3.9 and 3.12
7930.2 S ection 3.10.1 and 3.12
9370.2 2628.0 Total output
-91.5 m3/year
-12.0 mm/yearB alance560.0 kg/year
Horiz ontal groundwater outflow (GW o u t)
Open water body evapotrans piration (E T)
INP U T
OU TP U T
P recipitation (P )
Horiz ontal groundwater inflow (GW i n )
S urface water inflow (S W i n )
Vertical groundwater inflow (GW i n )
Water and Chloride balance of W023 for a period of 12 months (from Sep 2012 to Sep 2013)
Results Water and Chloride balance of W023
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Results Water and Chloride balance of W024
Volume
(m3
/year)
Cl-
concentration
(mg/L )
Cl- M as s
(kg/year)Comments
3116.2 8.0 24.9 S ection 3.1 and 3.12
1055.9 1097.0 1158.3 S ection 3.9 and 3.12
2923.4 8.0 23.4 S ection 3.11 and 3.12
7095.5 1206.7 Total input
789.8 1921.0 1517.1 S ection 3.9 and 3.12
5062.9 S ection 3.10.1 and 3.12
981.2
6833.8 1517.1 Total output
261.7 m3/year
34.3 mm/year-310.5 kg/year B alance
IN P U T
P recipitation (P )
H oriz ontal groundwater inflow (GW i n )
S urface water inflow (S W i n )
B are s oil evaporation (E T)
OU TP U T
H oriz ontal groundwater outflow (GW o u t)
Open water body evapotrans piration (E T)
Water and Chloride balance of W024 for a period of 12 months (from Sep 2012 to Sep 2013)
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Results Discussion
Water qualityW 023 W 024
E C (mS /cm) 3.8 to 7.43 0.18 to 7.92
pH 7.49 to 9.08 6.95 to 8.65
R edox potentia l (eh mV) - 97.5 to 205 - 65 to 201
Cl- (mg/L ) 1825 1921
TDS (mg/L ) 3448 4826
Water balance components of W023
Volume
(m3
/year)
Cl-
concentration
(mg/L )
Cl- M as s
(kg/year)
24% 2188.7 8.0 17.5 1%
21% 1980.0 1036.0 2051.3 64%
11% 1048.9 1036.0 1086.7 34%
44% 4061.1 8.0 32.5 1%
9278.7 3188.0
15% 1440.0 1825.0 2628.0
85% 7930.2
9370.2 2628.0
-91.5 m3/year
-12.0 mm/year
IN P U T
OU TP U T
P recipitation (P )
H oriz ontal groundwater inflow (GW i n )
S urface water inflow (S W i n )
Vertical groundwater inflow (GW i n )
560.0 kg/year
H oriz ontal groundwater outflow (GW o u t)
Open water body evapotrans piration (E T)
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The University of Western Australia
The University of Western Australia
Results Discussion
Volume
(m3
/year)
Cl-
concentration
(mg/L )
Cl- M as s
(kg/year)
44% 3116.2 8.0 24.9 2%
15% 1055.9 1097.0 1158.3 96%
41% 2923.4 8.0 23.4 2%
7095.5 1206.7
12% 789.8 1921.0 1517.1 100%
74% 5062.9
14% 981.2
6833.8 1517.1
261.7 m3/year
34.3 mm/year
IN P U T
P recipitation (P )
Horiz ontal groundwater inflow (GW i n )
S urface water inflow (S W i n )
B are s oil evaporation (E T)
OU TP U T
Horiz ontal groundwater outflow (GW o u t)
Open water body evapotrans piration (E T)
-310.5 kg/year
Water balance components of W0234
Uncertainty Component Error % Reference
Lake-to-Pan coeff 30% (Tweeda, Leblanca & Cartwright 2009)
Surface area (Surface water, ET) Winter (1981), TBRG - (Australian Bureau of Meteorology 2011)
Precipitation 16% - 26% Winter (1981), TBRG - (Australian Bureau of Meteorology 2011)
Groundwater (Hydraulic conductivity) 40% slug tests in Nabappie subcatchment – Variability in Average
Groundwater (Capture zone – ± 0.5) 10% Statistically
Cl- content in surface water Nabappie catchment 500 to 5000 mg/L Bourke (2011)
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Results Conclusion
• Flow-through wetlands • Direct contact with the water table of the surficial aquifer• Can be assumed that both of the wetlands are underlain by a silcrete hardpan• Hydrogeochemically different• Majority of inputs being sourced from groundwater and surface water runoff
components. • Considerable attention should be given to the surface water runoff component
because it may carry a significant amount of solutes to wetland W023 (Winter 1981).
W023 & W024
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Results Conclusion
W023
𝑆𝑢𝑝𝑒𝑟𝑓𝑖𝑐𝑖𝑎𝑙𝐺𝑊 𝑖𝑛
𝐷𝑒𝑒𝑝𝐺𝑊 𝑖𝑛
concept is supported by the occurrence of mature perennial vegetation in the northern half of wetland W023
𝐺𝑊 𝑂𝑈𝑇
The University of Western Australia
Results Conclusion
W024
concept is supported by the occurrence of mature perennial vegetation in the north-western part of wetland W024
𝑆𝑢𝑝𝑒𝑟𝑓𝑖𝑐𝑖𝑎𝑙𝐺𝑊 𝑖𝑛
𝐷𝑒𝑒𝑝𝐺𝑊 𝑓𝑙𝑜𝑤
The University of Western Australia
Iso- annual average total dissolved solids (TDS mg/L) curves along AA’
Results Conclusion
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Questions