Seasonal Watering Proposal for the Wimmera River System 2020-21 Report prepared for: Victorian Environmental Water Holder Report prepared by: Wimmera CMA April 2020 Wimmera CMA For further information on any of the information contained within this document contact: Greg Fletcher – Wimmera CMA Wimmera River at Antwerp, February 2020 Seasonal Watering Proposal for Wimmera River System | April 2020 | https://login.wcma.vic.gov.au/EDMS/Projects/6715 EWR Planning and 2 Impementation/Final Seasonal Watering Proposal Wimmera River System 2020-21.docx Wimmera CMA Publication details Acknowledgements Wimmera Catchment Seasonal Watering Proposal for The following individuals or Management Authority the Wimmera River System – groups have assisted in the www.wcma.vic.gov.au 2020-2021 preparation of this report. 24 Darlot Street Horsham VIC 3400 Date of publication: 17 April 2020 Erin Round Telephone 03 5382 1544 Tony Baker Facsimile 03 5382 6076 Ben Muir Author: David Brennan Copyright Greg Fletcher Stuart Harradine © Wimmera Catchment Kym Wilson Management Authority 2020 Scott Smith Richard Mintern Disclaimer Publications produced by the However, it is acknowledged that Wimmera Catchment the contents and views expressed Management Authority may be of within this report are those of the assistance to you, but the Wimmera Catchment Wimmera Catchment Management Authority and do not Management Authority and its necessarily reflect the views of employees do not guarantee that the parties acknowledged below. the publication is without flaw of any kind or is wholly appropriate VEWH for your particular purpose and Barengi Gadjin Land Council therefore disclaims all liability for GWMWater any error, loss or other CEWO consequence which may arise from you relying on any information in any Wimmera Catchment Management Authority publication. Seasonal Watering Proposal for Wimmera River System | April 2020 | https://login.wcma.vic.gov.au/EDMS/Projects/6715 EWR Planning and 3 Impementation/Final Seasonal Watering Proposal Wimmera River System 2020-21.docx Executive summary The Wimmera was again faced with challenging conditions in 2019-20 with another year of well below average streamflows. This continues to hamper the scale of possible watering actions and ecological outcomes within the region. Although this should not diminish the importance of the achievements to date with the focus on drought refuge management being vital for the ongoing survival of water dependent fauna. These achievements include: • additional water delivered to the Ranch Billabong, near Dimboola consolidating the environmental and cultural benefits; • avoidance of major flow/water quality related incidents (i.e. significant fish kills and algal blooms) despite very dry conditions and record high temperatures in December 2019; • conditions were suitable for the community to enjoy a full suite of recreational benefits on the Wimmera River with anglers enjoying the best fishing outcomes for many years. This proposal is for the use of available water in the Wimmera Catchment to maximise environmental water related outcomes in 2020-21 to prevent critical losses if conditions remain dry or enhance conditions if wetter conditions prevail. The proposal focuses on the regulated waterways of the lower Wimmera River, Burnt Creek, MacKenzie River, Bungalally Creek and Mt William Creek. The delivery of environmental water to these waterways is intended to support the environmental assets within these waterways such as riparian vegetation, iconic Freshwater Catfish and Platypus populations, locally vulnerable Southern Pygmy Perch and River Blackfish populations and threatened species such as Glenelg Spiny Crayfish and Western Swamp Crayfish. These waterways also contain many shared benefits including important cultural heritage sites, provide water for agriculture and public open spaces and sustains a variety of recreational activities such as fishing, swimming, boating and camping. Conditions continue to be extremely dry, although 2019-20 was marginally better than the record dry conditions in 2018-19. There were some natural flows from the upper Wimmera catchment for the first time since 2017 with modest but vital flows continuing along the Wimmera River through from late autumn to mid- spring. This enabled a postponement of environmental water deliveries until late spring to conserve volumes for use in 2020. The dry conditions led to allocations for the Victorian Environmental Water Holder entitlement only reaching 42% in March 2020 and so water carried over from earlier years was again vital for achieving outcomes in 2019-20. Therefore, regulated water availability is steadily reducing and as forecast, complete usage of Commonwealth Environmental Water Holder allocations took place in early 2020. Environmental watering has aimed to provide habitat and minimising deteriorations in water quality. They have to date been successful in achieving these aims with no major negative outcomes such as fish deaths. This proposal outlines the range of environmental watering actions for the Wimmera River system for the 2020-21 water year. Assuming the dry conditions experienced since 2017 persist, the focus for 2020-21 is again to prevent loss of high value refuge habitat and mitigating water quality declines (especially salinity) and a key to this will be the effective management of drought refuge pools throughout the system. This in turn reduces the likelihood of fish deaths, algal blooms and die back of fringing vegetation. Should conditions be wetter, than the objective is to continue to pursue vegetation and fish objectives by implementing baseflows and freshes. Fish objectives are achieved by providing baseflows throughout the year as well as spring/summer freshes to stimulate native fish breeding. They will provide opportunities for movement and increase available habitat given water has only been delivered to short sections of these waterways in recent years. Vegetation objectives are provided by implementing baseflows to maintain edge habitats and freshes to maintain existing plants, promote the establishment of new seed/plants in the growing season and maintain and encourage germination of aquatic plants. For the Wimmera River it is very important to provide regular baseflows and freshes to ensure adequate water quality through keeping salinity and dissolved oxygen concentrations at acceptable levels, particularly in the absence of large flows in recent years that would have mobilised and dispersed large quantities of organic material and salt. Environmental water will be adaptively managed as environmental conditions unfold throughout the year. Four management scenarios have been developed to cover the range of possible conditions. These scenarios and associated watering actions are outlined in Table 21. A wide variety of shared benefits will be provided by environmental watering actions, including watering for cultural outcomes at The Ranch in Dimboola as well as the recreational activities the Wimmera River provides that lead to enormous positive economic and health outcomes for the region. 4 Seasonal Watering Proposal for Wimmera River System | April 2020 | https://login.wcma.vic.gov.au/EDMS/Projects/6715 EWR Planning and Impementation/Final Seasonal Watering Proposal Wimmera River System 2020-21.docx Table of Contents Executive summary .................................................................................... 4 1. Introduction ......................................................................................... 7 1.2 Purpose ............................................................................................................................. 7 1.3 System Overview ............................................................................................................... 7 1.4 Flow Regime ...................................................................................................................... 8 1.5 Priority reaches and measuring points ................................................................................ 8 1.7 Water sources ...................................................................................................................10 2. Engagement ..................................................................................... 10 3. Shared Benefits ................................................................................ 11 3.1 Community Values ........................................................................................................ 11 3.2 Aboriginal Cultural Values ..............................................................................................12 4. Flow objectives and recommendations ............................................ 15 5. Seasonal review ............................................................................... 17 5.1 Climatic conditions this year and seasonal outlook.........................................................17 5.2 Review of 2019-20 watering, ecological observations and monitoring ............................19 5.2.1 Wimmera River summary ............................................................................................19 5.2.2 Ranch Billabong summary ...........................................................................................25 5.2.3 MacKenzie River summary ..........................................................................................26 5.2.4 Burnt Creek summary ..................................................................................................31