FinalWestern Summary Catchment Management Authority WarregoFinal River Summary Scoping Study 2008 WESTERN Contact Details Western CMA Offices: 45 Wingewarra Street Dubbo NSW 2830 Ph 02 6883 3000 32 Sulphide Street Broken Hill NSW 2880 Ph 08 8082 5200 21 Mitchell Street Bourke NSW 2840 Ph 02 6872 2144 62 Marshall Street Cobar NSW 2835 Ph 02 6836 1575 89 Wee Waa Street Walgett NSW 2832 Ph 02 6828 0110 Freecall 1800 032 101 www.western.cma.nsw.gov.au WMA Head Office: Level 2, 160 Clarence Street Sydney NSW 2000 Ph 02 9299 2855 Fax 02 9262 6208 E [email protected] W www.wmawater.com.au warrego river scoping study - page 2 1. Warrego River Scoping Study – Summary 1.1. Project Rationale and Objectives The Queensland portion of the Warrego is managed under the Warrego, Paroo, Bulloo and Nebine Water Resource Plan (WRP) (2003) and the Resource Operation Plan (ROP) (2006). At present, there is no planning instrument in NSW. As such, there was concern in the community that available information be consolidated and assessed for usability for the purposes of supporting development of a plan in NSW and for future reviews of the QLD plan. There was also concern that an assessment be undertaken of current hydrologic impacts due to water resource development and potential future impacts. As a result, the Western Catchment Management Authority (WCMA) commissioned WMAwater to undertake a scoping study for the Warrego River and its tributaries and effluents. This study was to synthesise and identify gaps in knowledge / data relating to hydrology, flow dependent environmental assets and water planning instruments. The key objectives of the study include: 1. Provide an overview of the surface water hydrology of the Warrego River and its tributaries. 2. Review existing literature on flow dependent environmental features of the region. 3. Summarise available hydrology related data. 4. Evaluate the impacts that water resource development has had, or could have, upon the regional flow regime. 5. Identify gaps in the available data sets, assessment tools and performance indicators and make recommendations to assist future water resource planning and management. 1.2. Study Area This scoping study examines the major distributary systems, in addition to the Warrego itself, as illustrated in Figure 1 Floodout channels of the Warrego system, May 2008. warrego river scoping study - page 3 Figure 1 - Hydrological Features of the Warrego Hydrologic data availability and an assessment on the impact of development on the flow regime have been presented separately for seven hydrologic regions identified for the purposes of this study. These are: 1. Warrego Basin down to Wyandra The upper part of the basin drains a large area with numerous creeks and rivers entering the Warrego River upstream of Wyandra. warrego river scoping study - page 4 2. Noorama and Widgeegoara Creeks These effluents leave the Warrego downstream of Wyandra and head south east, occasionally spilling into the Nebine. 3. Warrego River from Wyandra to NSW Border Downstream of Wyandra the river changes from a gaining river to a losing river due to the numerous effluents which leave the river. 4. Cuttaburra Creek The Cuttaburra Creek has it’s main offtake from the Warrego immediately downstream of Cunnamulla weir however other high flow offtakes occur upstream of the weir and some 20-30 km downstream of the weir. Flows from the Cuttaburra occasionally connect with floodwaters from the Paroo/Darling - on average every 15 years (QDNR, 2004). 5. Thurrulgoonia and Tuen Creeks Numerous effluents leave the Warrego downstream of Cunnamulla heading in a south easterly direction draining into extensive floodplain areas. Two key creeks in the region are the Thurrulgoonia and Tuen. 6. Irrara Creek The Irrara Creek leaves the Warrego just upstream of the NSW border and re-connects upstream of Fords Bridge. The Irrara also feeds the Kerribree and Green Creeks; the latter may connect back into the Warrego downstream of Fords Bridge. 7. Warrego River from Barringun to Darling The NSW section of the Warrego is examined separately due to different regulatory arrangements. A special section on cross border flows is included in the report as this is a key performance objective of the QLD ROP and warrants careful consideration and clarification in this study due to stakeholder concerns over this objective. 1.3. Methodology Literature and Data Review and Gap Analysis This project was based on a desktop study that collates and reviews information drawn from existing publications, reports and datasets. Some stakeholder consultation was undertaken from 5th – 7th May 2008, primarily for the purposes of obtaining copies of existing reports and information. Consultation also assisted the authors in obtaining a better appreciation of the region and highlighted a number of landholder concerns regarding water management. Given the scope of the project, extensive consultation was not possible. The consultation conducted was focused on landholders in the Lower Warrego in accordance with the requirements of the project brief. Impact Assessment The assessment of flow regime change due to development has been quantified through use of modelling data obtained from the Queensland Department of Natural Resource and Mines (QDNRM). Whilst the QLD model extends into NSW, there is scope for improvement in the representation of flows in the NSW section of the system. Therefore, WMAwater The consultants gained information by interviewing numerous landholders, including Paul and Debbie Kaluder of Naree Station, located on the Cuttaburra Channel. warrego river scoping study - page 5 developed an IQQM model for the NSW portion of the system using information provided from the NSW Department of Water and Energy. The information included licensing access conditions and details of infrastructure and cropping. It is important to note that due to the lack of streamflow data the model has not been verified and many additional improvements are possible. The two IQQM models were used to assess impacts on low flows, minor and moderate flooding for a number of sites on the Warrego and for major effluent creeks. Impacts on ecological assets were limited to “Directory of Important Wetland” sites, which have been assessed where there was suitable model data and sufficient information regarding the hydrological requirements of the wetlands. The assessment of ecological impacts associated with flow regime changes was limited to very broad comments. More sophisticated assessment tools are required to properly assess these impacts, as is discussed in the full report. The impact assessments presented in this scoping study assume that the available historic climate records are representative of future climate patterns. This assumption may not be valid, not only due to climate change, but also because the level of climate variability that might have occurred may not be well represented in the relatively short period of climate records available. The impact of climate change on the water resources and ecosystems of the Warrego was examined by CSIRO (2007), however a more detailed analysis of CSIRO’s results is warranted. It has not been possible to undertake this analysis for this report and as such it is recommended for future studies. 1.4. Overview of surface water hydrology Unlike southern basin rivers which generally experience some level of flow throughout the year, the Warrego is an ephemeral river. Flows generally occur in late summer to early autumn although winter flows also occur in some years. In addition to the seasonal basis of flows in the Warrego, wet and dry phases across groups of years can be established from the flow record. Wyandra is the point at which the Warrego changes from a river that is generally gaining in flow volume to generally losing in flow volume. The flow volume downstream of Wyandra is dramatically reduced due to the distributary nature of the system. For example, the average flow at Wyandra is approximately 550 GL per year whilst it is only 83 GL per year at Fords Bridge. Widespread flooding occurs periodically in the Lower Warrego, due to the gently sloping terrain, low banks and meandering nature of the drainage profile. These floods, which can occur without local rainfall, are highly desirable for maintaining fertility of the floodplain (Mottell, 1998). Many areas also rely on local runoff in addition to river flows. The total area inundated in the Warrego has been evaluated by several authors: o Mottell (1998) estimated, through community consultation, that a total of 457,772 ha is inundated in a major flood. o Kingsford et al. (2002) estimated historic areas of inundation based on analysis of Landsat imagery. The maximum area inundated was 284,410 ha in 1990 however it is important to note that this study does not represent total area of inundation in the basin1. o CSIRO (2007) reported that the maximum inundation area is approximately 2,066,000ha based on automated analysis of MODIS satellite imagery over the 2000-2006 period and extrapolation of this to 1990 – 200 period based on flow data. 1.5. Overview of Flow Dependent Environmental Features 1.5.1. Categories of Assets Flow dependent assets can be both structural and functional aspects of aquatic ecosystems. Structural aspects are generally the different types of physical aquatic habitats, eg rivers, floodplains, lakes, wetlands, etc. Functional aspects are generally the processes that are critical to providing the existence of the biota of aquatic ecosystems such as primary production, organic 1 The Noorama and Widgeegoara are not included. Estimations for Cuttaburra, Upper and Lower Warrego are based on a sample area of these zones which covers a significant proportion of area inundated but not the entire area. warrego river scoping study - page 6 carbon dynamics, food web interactions, etc. The flow dependent environmental assets for the Warrego have included instream waterholes, terminal and floodplain wetlands, and various vegetation communities.