2.6.2.4.1 Lateral


A general-head boundary was implemented in areas where the simulated aquifers continue beyond the groundwater model domain (Figure 12). As indicated by the three-dimensional hydrogeological model described in companion product 2.3 for the Clarence-Moreton bioregion (Raiber et al., 2016b), some aquifers simulated in the groundwater model do not terminate at the model’s northern and southern borders. Hence, general-head boundaries were used along the southern and northern sides of the groundwater model domain. Although the eastern side of the groundwater model domain follows the extents of the Walloon Coal Measures, the Richmond River alluvium does extend beyond this boundary as far as the coastline, so a general-head boundary was applied to the cells that intersect the Richmond River alluvium along this part of the groundwater model domain. The hydraulic conductance for the general-head boundary was allowed to vary by using three multipliers (Table 4) during the sensitivity and uncertainty analysis. Note that they were not transient parameters, that is, they were varied across simulations but kept constant during individual simulations.

The western side of the groundwater model domain that follows the extents of the Walloon Coal Measures, the eastern side of the groundwater model domain that does not intersect the Richmond River alluvium, and the bottom boundary of the groundwater model domain were all assumed to be impermeable, and were hence assigned no-flow boundaries.

Figure 12

Figure 12 Grid shell and grid lines of the Clarence-Moreton groundwater model

Red and blue cells show locations where General-Head Boundary and River packages were applied, respectively.

Table 4 Adjustable parameters associated with initial and boundary conditions during sensitivity and uncertainty analysis, and their corresponding bounds


Group

Parameter name

Initial value

Minimum

Maximum

Unit

Description

General-head boundary

GHB_N

5.04

0.01

1,000

na

Multiplier* for conductance of the north general-head boundary

GHB_S

0.80

0.001

10,000

na

Multiplier* for conductance of the south general-head boundary

GHB_E

1,000

0.1

1,000,000

na

Multiplier* for conductance of the east general-head boundary

Recharge package

RCH_1

1

0.2

2

na

Multiplier* for recharge of the recharge zone 1 (alluvium)

RCH_2

1

0.3

2

na

Multiplier* for recharge of the recharge zone 2 (Lamington Volcanics)

RCH_3

1.00

0.2

5

na

Multiplier* for recharge of the recharge zone 3 (Grafton Formation)

RCH_4

1.50

0.2

5

na

Multiplier* for recharge of the recharge zone 4 (Bungawalbin Member)

RCH_5

1.50

0.2

5

na

Multiplier* for recharge of the recharge zone 5 (Kangaroo Creek Sandstone)

RCH_6

2.00

0.3

5

na

Multiplier* for recharge of the recharge zone 6 (Walloon Coal Measures: Maclean Sandstone)

RCH_7

0.41

0.2

5

na

Multiplier* for recharge of the recharge zone 7 (Walloon Coal Measures: coal seams)

RCH_8

0.30

0.2

5

na

Multiplier* for recharge of the recharge zone 8 (Walloon Coal Measures: coal seams)

RCH_9

0.59

0.5

5

na

Multiplier* for recharge of the recharge zone 9 (Walloon Coal Measures: coal seams)

Drain package

DRN_C_2

1.00

0.2

5

na

Multiplier* for conductance of drain cells in layer 1

River package

Rinc

0.00

–0.5

0.5

M

Parameter to stochastically change river stages

rp1

5.07

0.1

1,000

m2d-1

Riverbed conductance at pilot point 1

rp2

86.89

1

1,000

m2d-1

Riverbed conductance at pilot point 2

rp3

47.35

1

1,000

m2d-1

Riverbed conductance at pilot point 3

rp4

45.82

1

1,000

m2d-1

Riverbed conductance at pilot point 4

rp5

5.48

0.1

1,000

m2d-1

Riverbed conductance at pilot point 5

rp6

1.03

0.01

1,000

m2d-1

Riverbed conductance at pilot point 6

rp7

0.01

0.0001

100

m2d-1

Riverbed conductance at pilot point 7

rp8

37.12

1

1,000

m2d-1

Riverbed conductance at pilot point 8

rp9

91.48

1

1,000

m2d-1

Riverbed conductance at pilot point 9

rp10

0.01

0.0001

100

m2d-1

Riverbed conductance at pilot point 10

rp11

49.20

1

1,000

m2d-1

Riverbed conductance at pilot point 11

rp12

59.37

1

1,000

m2d-1

Riverbed conductance at pilot point 12

rp13

77.76

1

1,000

m2d-1

Riverbed conductance at pilot point 13

rp14

4.95

0.1

1,000

m2d-1

Riverbed conductance at pilot point 14

rp15

27.42

1

1,000

m2d-1

Riverbed conductance at pilot point 15

rp16

5.08

0.1

1,000

m2d-1

Riverbed conductance at pilot point 16

rp17

32.89

1

1,000

m2d-1

Riverbed conductance at pilot point 17

rp18

20.14

1

1,000

m2d-1

Riverbed conductance at pilot point 18

rp19

596.68

1

10,000

m2d-1

Riverbed conductance at pilot point 19

rp20

526.61

1

10,000

m2d-1

Riverbed conductance at pilot point 20

rp21

599.62

1

10,000

m2d-1

Riverbed conductance at pilot point 21

rp22

506.91

1

10,000

m2d-1

Riverbed conductance at pilot point 22

*A multiplier is a dimensionless scalar to scale up/down parameters. For example, RCH_1 is a multiplier for the recharge of recharge zone 1 with a range from 0.2 to 2. This means that the recharge of recharge zone 1 was varied in a range between 0.2 and 2 times of the initial recharge of recharge zone 1.

na = not applicable

Data: Bioregional Assessment Programme (Dataset 1)

Last updated:
11 July 2017
Thumbnail images of the Clarence-Moreton bioregion

Product Finalisation date

20 October 2016
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