Poster Presentation International Conference on River Connectivity (Fish Passage 2018)

Assessing the effects and varied release mechanisms and operations and storage volume on thermal regimes downstream of a large reservoir (#225)

Laura Michie 1 , Simon Mitrovic 1
  1. Freshwater Ecology Research Group, University of Technology Sydney, Ultimo, N.S.W., Australia

Cold water pollution occurs below large dams when hypolimnetic water is released during periods of thermal stratification, with water temperatures being up to 16°C below predicted natural temperatures. Hypolimnetic releases can impact thermal regimes of downstream river systems for up to 300 km. These temperature changes can affect the health of aquatic biota such as algae, macroinvertebrates and fish. An innovative thermal curtain, being a large polymer structure suspended within the water column, was installed on a large dam on the Macquarie River, Australia in 2014 as an economical solution to mitigate cold water pollution by drawing epilimnetic water to the low-level fixed valve. Following implementation of the curtain, temperature improvements of 2.5°C were observed during summer whilst the dam was at low capacity. In 2016, the dam filled to full capacity, leading to a mixture of curtain, spillway and bottom releases. The effect of storage volume and varied release mechanisms from the dam will be discussed in terms of their impact on cold water pollution and downstream thermal regimes.