SS4.12 Linking Science with Management of Freshwater Resources
Date: Thursday, June 13, 2002
Time: 4:15:00 PM
Location: Carson B
 
BormansM, CSIRO Land and Water, Canberra, Australia, Myriam.Bormans@csiro.au
Ford, P, W, CSIRO land and Water, Canberra, Australia, Phillip.Ford@csiro.au
 
SETTING FLOW LEVELS FOR CONTROLLING CYANOBACTERIUM CYLINDROSPERMOPSIS RACKIBORSKI IN TROPICAL WEIR POOLS
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The frequently toxic cyanobacteria Cylindrospermopsis rackiborski occurs frequently in water supply weir pools and storages in tropical Australia and elsewhere. It flourishes under warm stratified conditions and its amelioration and management is an ongoing problem. We investigated its occurrence and growth in 3 separate water storages on the Fitzroy River in Queensland, Australia. We show that there is scope to reduce its prevalence by manipulation of the riverine flow to remove the stratification, and to raise the turbidity through the resuspension of the finely divided bottom sediments. These effects are not due solely to flushing the weirs but to “resetting” the optical and mixing depths so that conditions are inimical to buoyant cyanobacteria. The persistence of the sediment particles in the water column, and the size of the discharge are the two most important factors in determining the effectiveness of the procedure. Application of a hydrodynamic model can provide useful insights into defining the minimum discharge to be effective.