Algae was selected as an indicator of water quality and temperature was selected as the climate change component, in order to study the effect of temperature on algal growth. To achieve this goal, raw water samples were collected from two water treatment plants for a period of six months (started in June 2003).  Nitrate and phosphate concentrations were monitored, because they influence algal growth. The effect of temperature on nutrient levels was established for both plants, and the results showed that the maximum concentrations of nitrate and phosphate occurred in June and were 0.46 and 0.027 mg/l, respectively, whereas the minimum concentrations occurred in August were 0.2, and 0.006 mg/l.  Algae growth models (Michaelis-Menten kinetics and the Eppley temperature model) were applied to the data to compare the observed and calculated growth rates. The results showed that there will be a positive trend in algal growth.  Therefore algae could significantly impact on both treatment processes and public health in the future. Algae can decrease the treatment efficiency by clogging treatment units such as the screening unit. Also heavy loads of algae affect the filtration process by increasing the sedimentation rate. (Abstract shortened by UMI.)