1.1.5.3 Surface water flow

The Macquarie-Castlereagh river basin contributes about 8.4% of total runoff and uses slightly less than 4% of the surface water diverted for irrigation in the Murray–Darling Basin. The mean annual rainfall in the subregion is about 520 mm (1900 to 2011; see Section 1.1.2.1). Rainfall is slightly higher during January and February but is fairly uniform for the rest of the year. The mean annual modelled runoff is 35 mm (1985 to 2006) for whole of the Macquarie-Castlereagh river basin and is reasonably uniform throughout the year (CSIRO, 2008). The indicative runoff ratio based on mean annual rainfall and runoff is 6.7%. The mean annual modelled runoff over the ten-year period 1997 to 2006 is 33 mm, slightly lower than the long-term runoff value.

Sixty-three stream gauging stations in the Macquarie river basin, including six on the Bogan River and eight in the Castlereagh river basin, are still operational. These stations are managed by the NSW Office of Water and the majority of the stations are telemetered. The record lengths vary from a few years to more than 100 years. Summary statistics from some of the streamflow gauging stations in the Macquarie and Castlereagh river basins are given in Table 16 . Full details can be found in NSW Government (2013).

The impact of climate change by the South Eastern Australian Climate Initiative (SEACI) for the whole Macquarie-Castlereagh river basin indicated that 12 of 15 GCMs projected a decrease in future runoff showing a median reduction of 8% and 12% under 1°C and 2°C global warming, respectively (Post et al., 2012). See Section 1.1.2.3(Climate) for further details. The CSIRO (2008) study also indicated the effect of projected climate change on future runoff in the whole of the Macquarie-Castlereagh river basin is a likely decrease of runoff of about 6% for 2030 climate based on the median estimate.

Table 16 Selected open stream gauging stations in the Macquarie, Castlereagh and Bogan river basins within the Central West subregion and summary statistics

Site no.	Station Name and Location	Record Length (yr)	Start Year	Catchment Area (km²)^a	Mean Monthly Flow (GL)^a	Mean Annual Runoff (mm)
420003	Belar Creek at Warkton (Blackburns)	61.9	Dec-1951	133	1.05	101
420004	Castlereagh River at Mendooran	61.0	Nov-1952	3,600	7.79	26.8
420007	Castlereagh River at Binnaway	48.5	May-1965	1,590	5.98	46.4
420017	Castlereagh River at Hidden Valley	33.7	Feb-1980	1,166	3.98	41.6
421001	Macquarie River at Dubbo	128.0	Jun-1885	19,600	97.9	60.0
421003	Macquarie River at Wellington	104.8	Jan-1909	14,130	83.6	61.6
421004	Macquarie River at Warren Weir	115.0	Jan-1898	26,570	56.38	25.4
421011	Marthaguy Creek at Carinda	87.5	Apr-1926	6,475	12.00	22.8
421012	Macquarie River at Carinda	87.5	Apr-1926	30,100	11.94	4.95
421014	Macquarie River at Warren Town	80.8	Jan-1933	26,570	73.44	29.9
421018	Bell River at Newrea	74.3	Jul-1939	1,620	10.68	77.2
421022	Macquarie River at Oxley Station	72.8	Jan-1941	3,565	26.88	19.7
421031	Macquarie River at Gin Gin	59.3	Jul-1954	26,940	147.22	65.6
421039	Bogan River at Neurie Plains	54.5	May-1959	14,760	7.25	5.79
421042	Talbragar River at Elong Elong	49.0	Nov-1964	3,050	4.34	17.9
421083	Bogan River at Dandaloo	46.2	Aug-1967	612	2.76	57.2
421127	Macquarie River at Baroona	31.5	May-1982	25,700	91.8	42.8

^a The catchment areas and flow values are taken from the source given in the caption. There are inconsistencies in their values at different locations along the Macquarie River.

Source data: NSW Government (2013)

Last updated:

5 January 2018

Product Finalisation date

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