Of 70 weekly water samples taken at Warrandyte over the past five summers,only three have registered potentially unsafe levels of gastro-causingE. coli bacteria.
But downstream towards Kew and upstream to Launching Place,the Yarra's water quality generally worsens.
At the river's upper reaches in Launching Place,Millgrove and Warburton,summer bacteria levels have exceeded the trigger of 500 organisms in every 100 millilitres of water 14 times since December 2011.
As for the tests taken where the Chandler Highway crosses the river in Kew,there have been nine occasions when the water was teeming with an unsafe concentration of nasty micro-organisms.