Research Article 2014 WRR Burdekin sediment budget

Water Resources Research 10.1002/2013WR014386 Table 1. Gauged Sample Site Locations and Total Suspended Sediment (TSS) and Particle-Size Analysis (PSA) Data Collection Summary PSA Subset Sample Site Upper Burdekin River (Sellheim) Cape River Belyando River Suttor River Burdekin Falls Dam Overﬂow (capturing above sites) Bowen (Myuna) Burdekin River –Inkerman (end-of-catchment) Gauge Station/Location Water Years Sampled # TSS Samples # Samples Water Years 120002C: Burdekin River at Sellheim 120302B: Cape River at Gregory Dev. Rd. 120301B: Belyando River at Gregory Dev. Rd. a 120310A: Suttor River at Bowen Dev. Rd. 120015A: Burdekin River at Hydro Site 2005/2006–2009/2010 2005/2006–2009/2010 2005/2006–2009/2010 2005/2006–2009/2010 2005/2006–2009/2010 75 173 155 117 348 32 24 21 22 50 2005/2006–2008/2009 2005/2006–2008/2009 2005/2006–2008/2009 2005/2006–2008/2009 2005/2006–2008/2009 120205A: Bowen River at Myuna 120006B: Burdekin River at Clare (immediately upstream of Inkerman bridge) 2005/2006–2007/2008 2005/2006–2009/2010 140 b 227 b 110 12 2006/2007–2008/2009 2006/2007; 2008/2009 only c a 120310A gauge was installed after the 2005/2006 wet season. Streamﬂow for this site for the 2005/2006 water year was calculated by subtracting the Belyando River gauge (120301B) data from the downstream Suttor River (St Anns) gauge (120303A). b Individual water year load calculations by the LRE utilize any available preceding wet season TSS data (i.e., develops a site speciﬁc TSS concentration/streamﬂow relationship), which included 40 additional samples from 2002/2003 to 2004/2005 for the Bowen (Myuna) site and an additional 465 samples from 1986/1987 to 2004/2005 for the Burdekin River (Inkerman) site [Kuhnert et al. 2012]. c Burdekin River (Inkerman) data were collected by a different authority and not available for PSA. Opportunistic sample collection by the authors at this site during peak ﬂood con- ditions was conducted speciﬁcally for the purposes of PSA. subcatchment is also characterized by low undulating hills and steeper ridges in the upper catchment, and an incised valley system through volcanic hills [Roth et al., 2002]. Volcanic and sedimentary rock types domi- nate these two subcatchments (Figure 2). Extensive areas of erodible ‘‘Goldﬁelds’’ red duplex soils, black and red basaltic soils, and sodic duplex soils occur in the Upper Burdekin. Red-brown earths, yellow soils, granite/sandstone-derived gravely/sandy soils, and black earths cover large areas of the Bowen River catch- ment [Roth et al., 2002]. In comparison, the inland western subcatchments (the Cape, Belyando, and Suttor Rivers) drain gently undulating lowlands and alluvial plains, with wide multithreaded rivers, and with lower maximum elevations (300–450 m) located along the western boundary of the Cape and Belyando Rivers. Eucalypts, acacias (Brigalow Belt), and grasslands dominate these drier subcatchments, with average annual rainfall below 700 mm yr 21 (Figure 2). Remnant sedimentary basins and cracking clay soils form the domi- nant rock and soil types within these subcatchments, with gray/brown clays and red/yellow earths also widespread in the Belyando and Suttor subcatchments [Roth et al., 2002]. Cattle grazing across eucalypt sav- annah woodlands is the dominant (>90%) land use in the Burdekin catchment. More details about this region can be found in Roth et al. [2002] and the regional natural resource management body, North Queensland Dry Tropics website (www.nqdrytropics.com.au). € ppen-Gieger clas- The majority of the catchment is classiﬁed as a ‘‘hot semi-arid’’ climate (BSh) under the K o siﬁcation scheme [Peel et al., 2007], although the interannual and intra-annual rainfall and river ﬂood vari- ability of northern Australia is more pronounced than for other semiarid climates across the globe [see Petheram et al., 2008]. Annual rainfall variability is ‘‘moderate’’ to ‘‘moderate-high’’ across the Burdekin according to the Australian Bureau of Meteorology’s ‘‘index of variability,’’ representing the 10th and 90th percentiles over average rainfall (www.bom.gov.au/climate/averages/maps.shtml). Rainfall is strongly sea- sonal, with >80% of annual rainfall and river discharge occurring during the wet season months December to April [Lewis et al., 2006; Lough, 2007]. Mean annual rainfall also varies greatly across the catchment, rang- ing from >1500 mm yr 21 in the ‘‘tropical wet and dry’’ Upper Burdekin coastal ranges (north-eastern corner, Figure 2) to 500 mm yr 21 in the driest south-west corner of the Belyando subcatchment (Figure 2). This range is the largest for any watershed along the Australian east coast [Rustomji et al., 2009]. Locally this region is deﬁned as ‘‘seasonally-dry tropical,’’ a deﬁnition that we also adopt. Because of the seasonally dry tropical climate most streams within the Burdekin catchment are ephemeral, and streamﬂow predominately occurs as ‘‘ﬂood events’’ where ﬂows rapidly rise when fed by wet season rainfalls. Negligible ﬂows typically occur during the dry season (May–November). Wetter water years often result from monsoonal and cyclonic ~ o—Southern Oscillation cycles [Rustomji et al., 2009]. This cli- events, which are strongly modulated by El Ni n matic variability signiﬁcantly inﬂuences sediment runoff generation and transport each wet season; for example, drought-breaking ﬂoods carrying high-suspended sediment loads [Mitchell and Furnas, 1996; Amos et al., 2004]. This variability in annual Burdekin River suspended sediment export is captured in export measurements recorded between 1986 and 2010 that range from 0.004 to 15.74 (mean53.93, SD50.41) million tonnes per annum [Kuhnert et al., 2012]. BAINBRIDGE ET AL. C 2014. American Geophysical Union. All Rights Reserved. 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