Does a lack of vertical mixing reduce dissolved oxygen concentrations in the Swan River? Supervisors

Does a lack of vertical mixing reduce dissolved oxygen concentrations in the Swan River? 

Supervisors

• Nicole Jones
  Associate Professor, Oceans Graduate School

Students

• Sherry Fang

• Isaac Vaughn

Project Description

One of the hallmark signs of a decline in ecosystem health of the Swan-Canning Estuary is the more frequent and extent of low oxygen or anoxic events. Anoxic conditions directly impact flora and fauna, but can also lead to the remobilisation of nutrients from sediments, which in turn drives the formation of algal blooms. Here we will use a Nortek Signature 1000 to measure the mean and turbulent quantities over the water column next to the Department of Transport navigation marker Foam at approximately (31°59'33.9"S 115°50'18.0"E). The ADCP will be coincident with a mooring (funded by Riverlab) which will measure key water quality parameters, including dissolved oxygen, salinity, temperature, wind speed, direction and solar radiation at different water depths. We will evaluate the relationship of the key forcing: wind, tide, fresh water input and convective cooling with the water column turbulence and determine the resultant impact of the turbulent mixing on the dissolved oxygen concentration at different water depths.

Impact

The Swan River estuary has a history of eutrophication-related oxygen depletion, which results in poor water quality and fish deaths. We will develop a more sophisticated understanding of the relationship between the physical forcing, the resultant turbulent mixing and the impact on the dissolved oxygen concentrations. This will aid management of the river by:

1. identifying the most important processes that lead to low dissolved oxygen concentrations and
2. improving parameterisations for these processes in numerical models to allow prediction of low-dissolved oxygen events and thereby counter-measures to be mobilised.