Dhaka, a rapidly growing megacity, faces severe drinking water supply challenges due to rapid population growth, overdependence on groundwater abstraction, pollution of the peripheral rivers, and climate change impacts. To address the rising water demand, it is imperative to warrant sustainable water supply sources to ensure water security. This study identifies sustainable water sources for Dhaka for a planning horizon of 2050 by integrating statistical analysis, groundwater modelling, and water quality analysis. Surface water availability and quality assessment were conducted based on literature review. Groundwater modelling was carried out to assess the availability of the groundwater resources in the aquifers of Dhaka, effects of groundwater abstraction and to evaluate the safe yield. The model was developed to simulate the main hydrologic and hydraulic processes, and groundwater flow system by using modelling tools such as MIKE11 and MIKE SHE. Water quality analysis of the effluent from wastewater treatment plants and rainfall data analysis were conducted to assess alternative water sources. The study found that due to severe pollution, Dhaka’s peripheral rivers are unsustainable, while only the Padma and Meghna are viable long-term surface water sources. Groundwater modelling results indicated limiting the groundwater abstraction to 1000 MLD to prevent further aquifer mining. Some areas show high Iron and Manganese levels, requiring treatment and monitoring. Wastewater reuse from wastewater treatment plants shows high potential while Managed Aquifer Recharge offers limited contribution. Overall, the study will facilitate effective water supply planning and urban water management to ensure water security in Dhaka city.