Oral Presentation Australian Freshwater Sciences Society Conference 2022

Weir Pool Manipulation: An important management tool in the e-water toolkit (#22)

Nathan L Creeper 1 , Kerri L Muller 2
  1. Department for Environment and Water, Adelaide, SA, Australia
  2. Kerri Muller NRM Pty. Ltd., Adelaide, SA, Australia

Prior to European colonisation, the South Australian River Murray was a permanent, fast-flowing (lotic) river with large variations (~8 m) in water levels. Progressive catchment development and construction of weirs early in the 20th century led to tight river regulation and substantially reduced flows. Although the weirs were built to improve navigability and provide reliable access for consumptive use, they also led to the loss of the river’s wild nature, and the lower River Murray became a series of semi-connected and slow-moving (lentic) pools with very stable water levels. This fundamentally altered the ecology. The weirs remain prominent, important and persistent features of the modern, working river but they also offer significant opportunities to improve its ecology through improving water level management A newly developed Weir Pool Operating Plan for Locks 6 to 1 (Muller and Creeper 2021) has developed multiple management strategies to partially re-instating some components of river hydrology through strategic and sequential raising and lowering of weir pool water levels that will benefit a wide range of species and ecosystem processes. This type of weir pool manipulation (WPM) has become an increasingly common feature of routine river operations for the six weir pools in South Australia with a large zone of management influence (over 420 km of river channel, 6 discrete weir pools and up to 12,000 hectares of wetlands and floodplains). We will discuss the outcomes of more than 30 WPM events that have occurred over the past 20 years as well as the specific WPM actions, trials and investigations needed to be undertaken to increase operational capability and stakeholder confidence, to achieve the long-term vision for healthy, productive and resilient River Murray ecosystems and communities in coming decades.