The Effect of Gomphonema and Filamentous Algae Streamers on

Gomphonema, a freshwater diatom, is currently being studied to determine its effect on the capacity of hydroelectric canals and the structure of turbulent boundary layers. Gomphonema is the primary fouling organism present in Tarraleah No.1 Canal (operated by Hydro Tasmania) and was found to cause a 10% reduction in flow carrying capacity. Filamentous algae streamers up to 200mm long have also been observed in the canal. A recirculating water tunnel was used to measure the characteristics of the boundary layer flow over a 997mm x 597mm test plate covered with a biofilm grown in the field in an attempt to better understand the mechanisms for the increase in drag. Mean velocity profiles for the fouled test plate have been compared with results for a smooth test plate