The MacKenzie River in western Victoria is being used as a case study to develop an algal response model. This River has been substantially modified since the construction of Wartook Reservoir in 1887 for water supply purposes. Ten sites along the MacKenzie River were sampled every season over one year. Physical and chemical characteristics of water including pH, temperature, conductivity (EC), dissolved oxygen (DO), total suspended solids (TSS), total nitrogen (TN) and dissolved phosphorus (PO4-P) were measured. Biological properties of the algal periphyton communities including dry mass, ash-free dry mass, chlorophyll-a concentration and species composition of diatoms and soft algae were also measured at the same ten sites.The biomass and algal community structure were found to change along the river. The results indicate that algal periphyton communities, especially diatoms, are sensitive to changes in water quality and flow rates. It is clear that assemblages vary with season suggesting that response to flow will vary depending on the season of water release. These data will be used to develop an algal response model to help inform the delivery of flows down the waterway. Better design of consumptive flows down the waterway will be of particular focus.