Abstract: The LH-OAT sensitivity analysis method for the global parameters integrates the advantages of the LH sampling method with a random OAT method to ensure the robustness and effectiveness of the parameters. LH-OAT method must rely on complex computer program to achieve, however its application is limited because there is no generic procedures currently available in computer software. This paper investigated the generic procedures to apply LH-OAT method, and successfully used it for the phytoplankton dynamics model which was the core of the WASP water quality model. The results showed that in the condition of adequate supply of nitrogen and phosphorus, the most sensitive parameter was water temperature, followed by the endogenous respiration rate of phytoplankton and the carbon to chlorophyll ratio, and the fourth was zooplankton predation rates on phytoplankton. The reasonable range of each parameter was the key for the successful use of LH-OAT method．

Key words: sensitivity analysis, LHOAT method, WASP model, phytoplankton dynamics