The use of physically complex models is limited due to complexity in the measuring some of the parameters and calibrating others. The parameterization of these models is a very difficult task. To run the complex model for a single simulation can take a few hours to a few days, depending on simulation period and complexity of the model. The information contained in a time series is not uniformly distributed. So if we can find out the critical events which are important for identification of parameters, we can make parameterization easy for complex models. This methodology is effective in reducing time for simulation and complexity.