Skip to main content

This is a collection of resources related to estuary openings and environmental waterflows.

The Videos and Photos page has three videos relating to estuary openings.


Painkalac Roundtable 2, 27 March 2024:

Rory Nathan: Hydrology see saw and climate flip flop – Estuary openings and climate change

Painkalac Roundtable 1, 12 October 2023

The aim of this roundtable was to bring together Council, Agencies and local experts to discuss the artificial openings of the Painkalac Estuary with a focus on the science behind artificial openings, predicting failed openings and the conditions and methods for successful openings. Dr Sarah McSweeney and Callum Edwards presented their work on this topic.

AIDA Community Forum 21 Jan 2023:

  • CCMA Presentation – Jayden Woolley, Estuary & Environmental Water Manager – Estuary openings, environmental watering
  • Barwon Water Presentation – Jarod Scott, Coordinator Systems, Waterways & Catchments – Environmental releases and flows
  • Surf Coast Shire Presentation – Sharna Whitehand, Community Emergency Management & Resilience – Estuary openings, faecal contamination, flood mitigation

AIDA Forum 9 April 2016:

  • Barwon Water presentation – Shaun Cumming, Operations Manager – Water supply upgrade and flow regimes
  • CCMA presentation – Jayden Woolley, Strategy and Planning Manager – Environmental flows and estuary openings


2023 Painkalac Creek Estuary Opening data
Dates of openings together with creek height, rainfall and reservoir data.

Discharge data and water level on Painkalac dam and creek
Historic and live data from Rivers and Streams > Surface Water Sites > 235-Otway Cast Basin sites: 235220, 235232, 235257 and 235264

2023 Hydraulic gradient and wave height control the success of estuary artificial openings

  • Artificial entrance openings of estuaries need a grade of 1:60 to be successful
  • High offshore waves >4.30 m tend to close estuaries immediately
  • The grade at opening controls the rate of lagoon drainage
  • Opening at steeper grades mean peak outflow velocity is reached quicker
  • The tidal stage can influence rates of geomorphic change and estuary drainage

2023 The influence of geomorphology and environmental conditions on stratification in intermittently open/closed estuaries
Large changes in stratification occur as water drains from the estuary to the ocean potentially leading to a loss of of the top oxygenated layer of the water column during drainage which can cause fish kills. This study could be useful for estuary managers to predict how stratification in different types of Intermittently Open/Closed Estuaries will change during artificial openings and provide a proxy for predicting their response to climate change.

2020 Variability in infragravity wave processes during estuary artificial entrance openings
This study utilises artificial entrance openings of multiple Intermittently Open/Closed Estuaries in Victoria, Australia, to capture continuous hydrodynamic and geomorphic data throughout the opening cycle. We illustrate that water level oscillations in the infragravity (IG) band) are present in the basin during open entrance conditions. Our work identifies that changes in cross-sectional area, bed depth at the berm position, and offshore wave height control the magnitude of IG waves within the estuary basin.

2020 Field observations of geomorphic change during artificial openings
A dataset that enables us to understand what changes in entrance morphology occur during an opening and how these changes affect the rates of basin drainage. Findings: Calculating the hydraulic gradient is a cost-effective and easy way to assess the likely success of artificial openings. Ultimately this will reduce the need for reimplementation. The hydraulic gradient can also be used to predict drainage rates and determine when natural openings are likely to occur.

2020 The Effect of Mouth State and Morphology on Stratification in Victorian Estuaries
The results have identified, for the first time, the change in stratification that occurs during entrance openings and how these changes vary between openings of different magnitude. These results have also linked changes in stratification to changes in mouth morphology during the draining phase. Importantly, changes in morphology at the mouth are affected by (1) the timing of the artificial opening and (2) the initial channel dimensions. These variables can be easily manipulated by estuary managers. By having better control of the magnitude of the opening, large drops in Dissolved Oxygen can be prevented, preventing mass fish deaths.

2018 Predicting the entrance opening duration of Intermittently Open/Closed Estuaries (IOCE) in Victoria
This study uses historical records of entrance state and marine and fluvial conditions to develop a method of predicting the opening duration. The outcome is a predictive tool that managers can use to input both the current and forecast conditions to determine the probable entrance opening duration. This method will form a decision support tool for estuary entrance management that will have the capacity to learn and improve in future.

2017 The daily-scale entrance dynamics of Intermittently Open/Closed Estuaries
In this study, the entrance dynamics of three Intermittently Open/Closed Estuaries on the coast of Victoria, Australia, are monitored over a daily timescale following both artificial and natural openings. The influence of changing marine and fluvial conditions on the relative sedimentation rate within the entrance channel is examined. Based on the findings of this work, implementing a successful artificial entrance opening is dependent on reduced onshore sedimentation rates which occurred when wave energy is low (< 2 m Hs) relative to river flow.

1990 EEMS Background Report and User Manual
The Estuary Entrance Management Support System (EEMSS) is a decision support tool that guides estuary managers when making the decision whether or not to artificially open an estuary.

2023 Karaaf Wetlands Estuary Mouth Assessment
This review tested the assumption that keeping the Thompson Creek estuary in an open condition would improve flushing of the wetland to the west of Point Impossible Road and assist recovery of the impacted saltmarsh vegetation. Overall, the conclusion of this review is that opening of the estuary will not mitigate the effects of increased stormwater inflows on the Karaaf wetlands to the west of Point Impossible Road.

2020 Aire Valley Estuary Floodplain Project

The study, conducted by Alluvium Consulting and a Technical Panel of experts, considered the:

  • Impacts of the current estuary management on the environmental values of the Aire River estuary
  • Critical environmental needs of the estuary in terms of depth, timing and duration of floodplain inundation
  • Estuary opening processes that may adversely impact on environmental values, including protected species
  • Impacts of a closed estuary – drawing on existing inundation information

The findings included:

  1. Resilience of the system under climate change will be very important
  2. Artificial estuary mouth openings are restricting the potential of the estuary environmental values and putting environmental values at risk
  3. There is no environmental requirement to artificially open the estuary
  4. If artificial estuary entrance openings are required to protect other values (non-environmental), there are ways to minimise the environmental risks
  5. A further study is required to assess management options in the context of economic, social, cultural, and environmental values of the Aire Valley

Painkalac Valley Network home page

Painkalac Resource Repository
Explore the links below to learn about the importance, complexity and wonder of the Painkalac Valley – from the source to the sea:

Types of documents