Determining Photosynthesis Rate Constants in Lake Harapan Penang

Lake Harapan was created in 1990 to serve as a runoff detention pond in Universiti Sains Malaysia USM. The lake is eutrophic with occasional high levels of 300 mug/l chl a, with dissolved oxygen reaching 12 - 16 mg/l in the late afternoon and near anaerobic condition in late night. A decision was arrived at by USM to rehabilitate Lake Harapan recently, based upon previous model study completed in early 2005 by the authors. Model analysis indicates that USM campus contributes around 23 kg per day of BOD. Process rates have been estimated as follows: reaeration rate is 1.0 - 1.6 per day, respiration rate is 3.4 - 5.6 mg/l/day, and photosynthesis rate is 37.7 - 51.6 mg/l/day. This paper presents a summary of this modeling analysis, including a new reliable method to estimate reaeration rate. These process rates will be used to formulate a model to assist the rehabilitation.