Water in Selangor is getting scarce due to its rapid economic growth. A fast growing population and expanding urbanization in the state creates new demands for water availability. Thus, the present study analyses the effects of three different scenarios using Water Evaluation and Planning (WEAP) model to evaluate the plausible future water scenarios of water availability in Selangor. The first scenario is business as usual which is later referred to as reference in this study. Second, higher population growth and the third is the application of the demand side management onto the reference and higher population growth scenario. These scenarios were then used to calculate the impact on the supply – demand gap by the year 2050. Two catchments were used namely Selangor and Langat to illustrate the water supply and demand in the state of Selangor. The study then generates information for use in managing water allocations amongst economic sectors in Selangor as the explicit accounting in the description of the water supply and demand among the urban and industry water usage is advocated. Such detailed scenario simulation and the inclusion of previously unaccounted for factors like the higher population growth and water savings management can help to create awareness of potential future problems, inform water practices and suggest management alternatives. Results show that with proper water savings measures, water deficit within Selangor will be significantly reduced.