2.6.1.2.1 Review of surface water models used in the Namoi subregion


This section presents a review of surface water models previously used in the Namoi river basin and discusses the relevance of those to the surface water modelling undertaken for the BA for the Namoi subregion.

Table 3 lists the five surface water modelling studies carried out in the Namoi river basin using four different models. The Namoi subregion, which forms part of the Namoi river basin, is included in all of these studies.

Table 3 Surface water models previously used in the Namoi river basin


Study

Model used

Reference

Murray-Darling Basin Sustainable Yields

SIMHYD, IQQM

CSIRO (2007)

Namoi Catchment Water Study

LASCAM

Schlumberger (2012)

Namoi river basin modelling

IHACRES

Croke et al. (2006)

NSW surface water modelling for water sharing and management

IQQM (Sacramento)

NSW Department of Water and Energy (2008)

Murray–Darling Basin Plan

Namoi IQQM

MDBA (2012)

Table 4 gives a summary of surface water modelling studies within the Namoi river basin. The right to publish the modelling data (as required in the Bioregional Assessment Programme) from these studies is either unavailable or uncertain in all except those from the Namoi Catchment Water Study and CSIRO’s Murray-Darling Basin Sustainable Yields Project. Except for the Namoi Catchment Water Study, none of the earlier studies assesses the impacts of coal resource development. Consequently, only the LASCAM model used in the Namoi Catchment Water Study is further reviewed in this section.

Table 4 Summary of Namoi surface water modelling studies and suitability of their use in the bioregional assessment


Study

Domain covered?

Coal resource development assessed?

Modelled streamflow data available?

Data publication right?*

Simulation time span (years)

Location density of flow nodes (model nodes)

River system modelling?

Use of climate trend

Murray-Darling Basin Sustainable Yields

Yes

No

Yes

Yes

112

(from 2007)

5 x 5 km grid (~1600 grids)

Yes

Yes

Namoi Catchment Water Study

Yes

Yes

Yes

Yes

90

(from 2011)

99

Noa

Yesb

Namoi river basin modelling

Yes

No

No

Na

No future scenario modelled

17

Noc

No

NSW surface water modelling for water sharing and management

Yes

No

Unsure

Partially

114

(from 2006)

Unsure

Yes

Yes

Murray–Darling Basin Plan

Yes

No

Unsure

Unsure

114

(from 2009)

Unsure

Yes

Yes

aRiver routing was done.

bDetailed climate trends not described in Schlumberger (2012).

cRiver modelling using inflow to the reach (no consumptive use and regulation modelled).

na = not available

*right to publish modelled data

Namoi Catchment Water Study

Schlumberger Water Services (SWS) used the LASCAM hydrological model (Viney et al., 2000; Sivapalan et al., 2002) for surface water modelling in the Namoi Catchment Water Study. The modelling domain covers eastern and central surface water catchments above a location approximately 6 km upstream of Narrabri comprising the Peel River catchment and areas upstream of Keepit Dam (Schlumberger, 2012). Thus, SWS’s domain covers all coal mine development sites and most of the area of coal seam gas (CSG) future development sites identified in the CRDP for the Namoi subregion.

Data and model calibration

LASCAM was used on a series of 99 linked subcatchments, which were characterised in terms of land use and vegetation characteristics, and stream channel geometry. The input data used were rainfall, evaporation, vegetation cover, land use and soil type. A daily time step was used in calibrating the model using input data from 1996 to 2010. Among other observed variables the daily streamflow and flow duration curves were used to compare the modelled and observed results in calibration. A reference climate was derived from repeating 20 years of data from 1990 to 2009 and simulations were run for 90 years from 2010 to 2100 using the reference climate. No mention of river system modelling or river routing is found in Schlumberger, (2012), though routing is an integral component of LASCAM.

Scenarios used

Eight different development scenarios were modelled in the Namoi Catchment Water Study (Table 5). Of these, the scenario most comparable to the baseline future for the BA for the Namoi subregion is scenario 1, which considers six approved open-cut coal mines and one underground coal mine (Table 5). The difference between scenario 1 and the BA baseline is that the former includes the Canyon Coal Mine, which, since it closed in 2009, is not included in the latter.

The scenario in the Namoi Catchment Water Study that most closely approximates the CRDP future in BAs is scenario 2 which augments scenario 1 with two new open-cut coal mines, two expanded open-cut coal mines, one underground coal mine and two CSG developments. Scenario 2 includes one CSG field (Santos’ Bando CSG field) as well as the Canyon Mine which are not in the CRDP. Conversely, scenario 2 does not include the Vickery Coal Project or the Narrabri South underground coal mine, both of which are in the CRDP.

The Namoi Catchment Water Study reports that the main impacts to surface water will be derived from open-cut mining with little impact predicted from CSG or underground mine development. Predicted differences in long-term (2010–2100) average streamflow between scenario 1 and scenario 2 are reductions of approximately 0.1% at three locations in the Namoi River (approximately at Gunnedah, Boggabri and Narrabri) and approximately 0.0% and 0.2% at two locations in the Mooki River (Breeza and Ruvigne).

Table 5 Development scenarios used in Schlumberger’s modelling study


Scenario number

Description

Number of open-cut mines

Number of underground mines

Number of CSG fields

0

No current or future mining or CSG

0

0

0

1

Approved mines and CSG production

6

1

Pilot holes only

2

Approved and planned mines and CSG

10

2

2

3

Extensive and widespread mining and CSG

24

7

8

4

Extensive and widespread mining only

24

7

Pilot holes only

5

Extensive and widespread CSG only

6

1

8

6

Half underground mines beneath alluvium

24

7

8

7

More rapid development of coal and gas resources than in scenario 3

24

15

8

CSG = coal seam gas

Data: Schlumberger (2012)

Last updated:
6 December 2018
Thumbnail of the Namoi subregion

Product Finalisation date

2018

ASSESSMENT