Water is the prime determinant resource ensuring theSustainability sustainability of urban regions. Since historical times, this prime resource has been freely available both as a surface and underground resource. With the rapid pace of urbanization and industrialization coupled with the growing human population and unwanted interventions, especially in big metropolitan cities, water resources have largely been tapped and over-extracted leading to its depleting nature. The burgeoning climate changeClimate change adds to this grim scenario. The global rise in temperature results in more evaporation from water bodies and transpiration from green plants, thus, disturbing the natural and healthy hydrological cycle. It results in extreme weather events like floods and droughts. The growing megacity of Delhi is no exception to this. Unscientific, irrational, and unconscious use of water during monsoon and off-monsoon periods often leads to problems of water abundance leading to flood scenarios and scarcity. The study is based on secondary data collected from the Census of India, Master plans of Delhi, Central, State, and Ground Water Boards, and the Indian Meteorological Department. The study intends to estimate and calculate water balanceWater balance based on the Thornthwaite-Mather water balance model for Delhi and to propose innovative measures to manage water during water deficit and water surplus months to ensure durability, self-reliance, andSustainability sustainability of water in the long run. This study is based on the Thornthwaite-Mather water balance model as proposed and applied by Nugroho in calculating the water balanceWater balance in the Tambakbayan watershed of Yogyakarta in Indonesia. Water Surplus and Water Deficit months are identified and depicted spatially. The paper suggests innovative practices like rainwater harvestingRainwater harvesting, construction of green buildings, storage and recovery of aquifers, installation of shade clothShade cloth, etc. The findings will help in the proper estimation and identification of water surplus and water deficit months resulting in rational allocation and utilization of water, thus ensuring hydrologicalSustainability sustainability of the area.