Table : Water storages and weirs in the Murrumbidgee, Lowbidgee and Yanco systems. Name Description Operation Associated Assets Blowering Dam Located on the Tumut River, which is a major tributary of the Murrumbidgee River. Regulates approximately 87 per cent of all inflows (CSIRO 2008). Stores both natural flows and waters released from the Snowy Mountains Hydro-electric scheme. 1,628 GL capacity (Green et al. 2011). On average 1,460 GL/yr released into the Tumut River which then enters the Murrumbidgee River. There is a 9,300 ML/d flow constraint at Tumut to avoid erosion thresholds in the channel downstream and localised flooding. This is also the maximum release capacity at full supply level. All assets downstream of the dam on the Murrumbidgee River and Tumut Rivers. Burrinjuck Dam Located on the Murrumbidgee River. Burrinjuck Dam regulates approximately 77 per cent of all inflows (CSIRO 2008). 1,026 GL capacity (Green et al. 2011). On average 1,510 GL/yr released into the Murrumbidgee River. Maximum release rate at full supply level is 29,100 ML/d. There is a 32,000 ML/d constraint at Gundagai1. All assets downstream of the dam on the Murrumbidgee River. Berembed Weir Located on the Murrumbidgee River 60 km downstream of Wagga Wagga, Berembed Weir supplies the MIA’s Main Canal. Diverts approximately 6,400 ML/d along the Main Canal (Shields & Good 2002). The Main Canal carries approximately 80 per cent of all water which is diverted for irrigation purposes in the MIA (Shields & Good 2002). This structure is primarily used for irrigation diversions, and is not a storage structure. Maximum capacity of 6,700 ML/d to the Main Canal (Green et al. 2011). Lower Mirrool Creek Floodplain Barren Box Swamp Fivebough Swamp Tuckerbil Swamp Selected wetlands
swamp filled via local run-off during winter and spring then dried out over summer due to evaporation and infiltration. Management of the wetland is targeted at supporting the annual wet/dry sequence (except for areas of permanent inundation associated with the discharge of treated sewage effluent from Leeton sewage treatment plant). A volume of 500 megalitres is required to inundate the swamp (approximately 60 per cent of the swamp is inundated by 500 megalitres), with the last managed event occurring in early 2010. Fivebough Swamp has four management zones (which are contiguous) (Fivebough & Tuckerbil WMT 2002): Zone 1 (eastern portion)—covers approximately 60 per cent of the swamp and requires inundation to a depth of 45 centimetres in eight out of 10 years (Biosis Research & WI-O 2006) Zone 2 (western portion)—requires shallow water (i.e. 3 centimetres) inundation in nine out of 10 years (Biosis Research & WI-O 2006). A portion of Zone 2 is continually wet from irrigation of treated sewage effluent Zone 3 (entrance area)—predominantly dry zone that does not have ecological water requirements Zone 4 (north-western portion)—is an ephemeral wetland favoured by larger wading birds. The water management objective is to support temporary wetlands, but the volumes of water required to achieve this are not known. Water enters this area via an escape during high rainfall events or via Zone 1 when water levels are sufficiently high in winter and spring. Current management of Fivebough Swamp opens the southern regulatory structure on the contour drain from June until November to allow natural rainfall run-off to enter the wetland. The Fivebough and Tuckerbil Swamps Management Plan notes that the length of time varies depending on the season. Artificial watering of the swamp has been undertaken using water supplied from the Murrumbidgee River through the MI supply channels. The optimum time for this to be undertaken from a delivery aspect is between July to October. This is the low-regulated season and is after the annual maintenance period in the MIA channels. Water for managed events would be supplied via Murrumbidgee Irrigation’s supply channels, which requires liaison with MI. Tuckerbil Swamp Tuckerbil Swamp is a natural inland drainage depression covering 289 hectares. The objective for the management of Tuckerbil Swamp is to maintain and protect habitats for
Wanganella Swamp Maintain and improve wetland vegetation communities. Late winter-spring 1,500 ML required if delivered directly to inundate all 470 ha of Wanganella Swamp (Webster & Davidson 2010). Up to 20,000 ML is required if flows are delivered via Billabong Creek via the Murray Irrigation Limited system (E Wilson 2011, pers. comm., 19 September). Note: This amount does not take into account transmission losses and evaporation. Maintain open water areas and exposed muddy margins. Late summer-autumn Maintain known colonial waterbird breeding sites in ‘event ready’ condition. Late winter-spring Dry Lake Maintain and improve river red gum forest and woodland communities. Winter-spring Further assessment required. However, flows in excess of 28,100 ML/d at Wagga Wagga will cause Molly’s Lagoon and Dry Lake to commence-to-flow. Maintain and improve wetland vegetation communities. Late winter-spring Mundoora/Wilson Anabranch Maintain and improve river red gum forest and woodland communities. Winter-spring Further assessment is required. However, flows in excess of 165 ML/d at Yanco Bridge will cause Wilson Anabranch to commence-to-flow. Mundoora Anabranch flows daily as it is the routed section for Yanco Creek. Kerribirri Swamp Maintain and improve wetland vegetation communities. Late winter-spring Further assessment required. ‘Rhyola’ Depressions and Maintain and improve wetland vegetation communities. Late winter-spring Further assessment required. Box Swamp on ‘Blue Gate’ Maintain and improve wetland vegetation communities. Late winter-spring Further assessment required.
invasive species introduction (especially in the case of the Mirrool Creek and Yanco Creek systems) flooding of properties and infrastructure. Mitigation strategies Options for the mitigation of risks associated with environmental water delivery and use are presented in . Strategies for alleviating risks include consideration of site-specific issues, such as the frequency and duration of antecedent flows and the current condition of vegetation and soils, to river-wide issues such as control of return flows and salt harvesting, and management options such as the potential for flushing flows, control of return flows, complementary land-management actions, and options for managing the spread of invasive species.
Water Delivery Costs In the Murrumbidgee catchment the principle water infrastructure operators are SWC, MI and CICL. These organisations operate a variety of irrigation infrastructure across the catchment, which are also used for the delivery of environmental water. Private landholders may also permit the canals and channels on their properties to be used for the delivery of environmental water. Ideally, the most cost-effective means of water delivery should be adopted, particularly from an operational perspective, but this is not always feasible or conducive to achieving optimal environmental outcomes. In terms of water-delivery costs, a number of factors must be considered in the delivery of environmental water: the different delivery paths and ownership of infrastructure timing of releases (i.e. does the watering action coincide with delivery of water for landholders?) system capacity delivery mechanisms (i.e. gravity fed or pumping?). The following sections provide an overview of water-charge arrangements relevant to the delivery of environmental water in the Murrumbidgee River catchment. Water-charge arrangements State Water Corporation As the entity responsible for the delivery of bulk water in the regulated river systems of NSW, State Water Corporation (SWC) recovers its operational costs through water charges. The level of water charge depends upon a number of factors including the type of licence (general or high security), the catchment and the volume. The Independent Pricing and Regulatory Tribunal (IPART) determines the price structure for water delivery, with cost reviews considering water availability and costs associated with maintenance and upgrade of water infrastructure owned and operated by SWC. IPART Determination No. 2 specifies the 2011–12 (effective 1 July 2011) regulated river prices that apply to water delivered by SWC in the Murrumbidgee Valley (). Note that an additional levy applies for the Yanco/Colombo system (an extra $0.90 per megalitre/unit share of entitlement).
environmental watering on the Lowbidgee Floodplain. temperature, dissolved oxygen and water depth) Fish community abundance, diversity and species richness. Waterbird community abundance, diversity and species richness. Frog community abundance, diversity and species richness. Note: Not all parameters were monitored at all sites. South Eulimbah Telephone Creek Wagourah Lagoon Paul Coates Swamp and Redbank Canal Mercedes Swamp Two Bridges Swamp Monkem Creek Avalon Swamp Warwaegae Swamp/Dam 1AS Regulator Channel North Redbank Canal (fish only)
Table : Potential biotic variables and parameters for monitoring ecological response to environmental flows. (Adapted from Wilson et al. 2009) Parameter* Ecological Objective Monitoring Method Rationale Responsibility Water chemistry Maintain water quality in channels, pools and wetlands. Prevent stratification in deep pools. Salinity pH Dissolved oxygen Temperature Turbidity Conductivity Suspended solids Dissolved organic carbon Phosphorus and nitrogen Provides data on physicochemical responses to environmental flows and also assessment acid sulphate chemical response. Sampling and analytical methods are well established. Some data is likely available from previous monitoring conducted in the catchment. NOW manages current instantaneous salinity, dissolved oxygen, turbidity, pH and temperature monitoring at a number of gauging stations in the system. Algae Maintain water quality in channels, pools and wetlands. Prevent stratification in deep pools. Chlorophyll a Diatom cell abundance and taxonomic composition Pelagic cell abundance and taxonomic composition Benthic algal biomass and taxonomic composition Base of aquatic food webs. Exhibit relatively rapid responses to flow variability. High public awareness. NOW manages an algal monitoring program that provides counts of algae. Macrophytes Maintain and improve semi-permanent aquatic vegetation communities to good condition. Shoot density Taxonomic composition Seedbank germination Macrophytes are a key structural component of aquatic ecosystems. Potential rapid response to flow variability. NOW and OEH monitor the condition of selected wetlands throughout the system. Floodplain vegetation Maintain and improve river red gum forest/woodland, black box woodland and lignum communities. Species composition, abundance and biomass Seedbank emergence Key structural component of floodplain ecosystems. High public awareness. Management focus. Potential availability of historic data sets and monitoring sites. Relatively rapid response to NOW and OEH monitor the condition of selected wetlands throughout the system. MI monitors vegetation rehabilitation in Barren Box Swamp.
overbank flows. Amphibians Maintain southern bell frog breeding sites in good condition, and support breeding events. Abundance and taxonomic composition Spawning activity Public awareness. Relatively rapid response to flow variability. OEH monitors frog populations at selected sites throughout the system, especially southern bell frog sites in the Lowbidgee. Fish Maintain water quality in channels, pools and wetlands. Prevent stratification in deep pools. Maintain and improve longitudinal and lateral connectivity. Abundance and taxonomic composition Spawning activity Size structure Public awareness. Minimal laboratory effort required, apart from otolith analyses of spawning timing. Potentially rapid response to flow variability in spawning activity. OEH monitors fish populations at selected sites throughout the system. NSW Fisheries previously sampled fish communities throughout the Murrumbidgee River catchment (Gilligan 2005). Waterbirds Maintain known colonial waterbird breeding sites in good condition, and support breeding events. Abundance and taxonomic composition Fledgling success Public awareness. Relatively rapid response to flow variability. OEH monitors waterbird populations at selected sites throughout the system, especially rookeries in the Lowbidgee. Waterbird populations at Tuckerbil and Fivebough Swamps are monitored by the Fivebough and Tuckerbil Wetlands Trust. Hydrologic connectivity Flows are delivered in a timely and effective manner. Maintain and improve longitudinal and lateral connectivity to protect and restore the endangered ecological community, including threatened species. Water level and timing, magnitude and flow frequency Inundation area mapping Hydrological connectivity is important for transport of sediments, nutrients and energy and also the river channels and wetland connectivity. Hydrological connectivity is also an important vector for movement of aquatic biota and contributes to ecosystem resilience. NOW manages current instantaneous level and discharge at a number of gauging stations in the system. * Any monitoring undertaken should be checked for consistency with MDBA and Australian Government water strategies and plans
Table A: Environmental assets in the Murrumbidgee, and their watering history and current condition (as of October 2011). Environmental asset Watering history Current condition 1. Murrumbidgee River (Gundagai to Maude) Information on the watering history of Mid-Murrumbidgee wetlands is piecemeal because there is so many of them they are managed by different agencies, natural resource management organisations and private landholders, each with their own management focus and priorities. The following dot points provide more specific information for some Mid-Murrumbidgee wetlands. The condition of Mid-Murrumbidgee wetlands was considered critical and declining in 2009, with condition worsening from the uplands in the east to the lowlands in the west of the catchment. In general, recent natural flooding (spring and summer 2010–11) will have alleviated stress on some wetlands, and provided flushing flows for others, and their condition can be expected to improve in the short-term. Selected IMEF sites were watered in 2000, 2001 and 2005. Then all sites were watered in 2009, and again in late 2010 when the Murrumbidgee River naturally inundated. (IMEF sites include Sunshower Lagoon, Berryjerry Lagoon, Iris Swamp Lagoon, Molly’s Lagoon—Dry Lake, and Gooragool Lagoon.) IMEF sites were considered in critical-to-poor condition in August 2009. The IMEF sites would have been naturally inundated in late 2010, and are currently wet or drying. Most river-fed wetlands in the Murrumbidgee River floodplain from Burrinjuck/Blowering Dams to Narrandera were watered in spring 2000 or spring 2005. Sites were considered in poor-to-good condition in August 2009. These sites would have been naturally inundated in late 2010, and are currently wet or drying. Some Carrathool to Maude Weir floodplain wetlands were watered 1996, and others in 2000. These wetlands were considered in critical to poor condition in August 2009. Some of these sites would have been naturally inundated in late 2010, and are currently wet or drying.
Maude Weir Lagoon was filled in December 2009 with approximately 30 ML of EWA, then topped up with approximately 3 ML of EWA in December 2009 and again in May 2010. No information relating to the specific condition of Maude Weir Lagoon was available. Given its location in the lowlands of the floodplain it is assumed the lagoon was in poor condition prior to watering in 2009. If the lagoon was inundated during the recent natural flood, its condition may have improved, at least for the short-term. 2. Fivebough Swamp Fivebough Swamp received EWA water in 2005. Then in May 2010 it was inundated with 1,019 ML of EWA. On this occasion the site was filled to its highest level in more than 10 years. Although altered from its natural condition, Fivebough Swamp is considered in good condition (M Schultz [Fivebough & Tuckerbil Wetlands Trust] 2011, pers. comm., 8 November). 3. Tuckerbil Swamp Tuckerbil Swamp was watered using 500 ML of EWA in 2005. Since 2005 it would have received intermittent inflows from local rainfall events. Although altered from its natural condition, Tuckerbil Swamp is considered in reasonable condition (M Schultz [Fivebough & Tuckerbil Wetlands Trust] 2011, pers. comm., 8 November). 4. Barren Box Swamp Barren Box Swamp was used as a drainage basin for Murrumbidgee Irrigation Limited water, so it was permanently wet from the 1970’s to 2003. Works commenced in 2005 divided the wetland into three management ‘cells’, with one designated as a rehabilitation area for wetland habitat. This ‘wetland cell’ dried in 2003, until it was watered in October/November 2010. Barren Box Swamp was previously in poor condition, with the wetland cell supporting numerous weeds, and dry since 2003. The wetland cell is currently managed as per the Barren Box Wetland Rehabilitation Plan (MI 2008), which aims to protect and enhance the environmental values of the wetland. Aerial seeding of black box was planned for late November 2010. Control of alligator weed is ongoing in the Swamp system. 5. Lower Mirrool Creek The last end-of-system flow in the Lower Mirrool Creek (to The floodplain is currently considered in poor-to-critical
Floodplain the Lachlan River) was in 1989. Prior to 2003 small ‘forced releases’ routinely inundated the floodplain immediately west of Barren Box Swamp. This ceased by chance in 2003, when the drought dried Barren Box Swamp, and then by design in 2005 when works at Barren Box Swamp were commenced to improve its efficiency. High summer rainfall in summer 2010 filled wetlands throughout the system, with some flows reported in the lower reaches of Mirrool Creek (J Maguire [OEH] 2011, pers. comm., 9 August). condition. Areas downstream of Barren Box Swamp were overwatered for decades, leading to a decline in their condition. Black box woodland and associated wetlands further west in the floodplain are also considered in poor to critical condition, but from a lack of water. 6. Lowland river-fed wetlands (Balranald to Murray River junction, including ‘the Junction’ wetlands) Targeted billabongs were watered by OEH. Condition is considered poor. Some wetlands have not been watered since 2000. 7. Lowbidgee Wetlands (also see Table below) The North Redbank system experienced good flooding as far south as Glen Avon in 2010. As the lower end of the North Redbank wetland (off North Redbank Channel on the Lowbidgee floodplain) 3000 ha of river red gum wetlands were inundated in autumn 2010 using 1,600 ML of CEW supplementary water, 400 ML of NSW supplementary water, 1,000 ML of Lowbidgee share, and 5,000 ML of NSW environmental water allowance water. This was the first watering for five years. 1,800 ha of Paika-Narwhie was flooded with NSW Current condition is considered good.
Commonwealth environmental watering objectives Ecological Watering Objectives Management Objectives Management Actions Extreme Dry Avoid damage to key assets Avoid critical loss of threatened species and communities Maintain key refuges Avoid irretrievable damage or catastrophic events Water refugia and sites supporting threatened species and communities Undertake emergency watering at specific sites of priority assets Use carryover volumes to maintain critical needs Dry Ensure ecological capacity for recovery Support the survival and growth of threatened species and communities, including limited small-scale recruitment Maintain diverse habitats Maintain low-flow river and floodplain functional processes in sites and reaches of priority assets Water refugia and sites supporting threatened species and communities Provide low flow and freshes in sites and reaches of priority assets Use carryover volumes to maintain follow-up watering Median Maintain ecological health and resilience Enable growth and reproduction and large-scale recruitment for a diverse range of flora and fauna Promote higher connectivity Support high-flow river and floodplain functional processes Prolong flood/high-flow duration at key sites and reaches of priority assets Contribute to the full range of in-channel flows Use carryover to provide optimal seasonal flow patterns in subsequent years Wet Improve and extend healthy and resilient aquatic ecosystems Enable growth, reproduction and large-scale recruitment for diverse flora and fauna Promote higher connectivity Support high-flow river and floodplain functional processes Increase inundation duration and extent across priority assets Contribute to the full range of flows, including overbank Provide Use carryover water to optimal seasonal flow patterns in subsequent years
Minor Localised damage to environmental values and/or connected waters/other parts of the environment; temporary loss of water supplies Minor public inconvenience No injuries No economic impacts Minor public inconvenience A small amount of water will be lost and this will have a small impact on the environmental outcomes Insignificant Negligible impact on environmental values and/or connected waters/other parts of the environment; no detectable impacts on species No public inconvenience No injuries No impacts on private property No infrastructure damage Water loss will be minimal and will not affect the planned outcomes of the watering event LIKELIHOOD CONSEQUENCE Insignificant Minor Moderate Major Critical Almost certain Low Medium High Severe Severe Likely Low Medium Medium High Severe Possible Low Low Medium High Severe Unlikely Low Low Low Medium High Rare Low Low Low Medium High