Stable environmental isotopes are ideal tracers because they are constituents of the water molecule itself. Isotopes are crucial aspects for water quality and water management. Determining water residence time with a good accuracy for a hydrological process that is usually complex to model and predict is a challenging task. Through years, researchers and scientists have developed different approaches to accurately estimate water residence time. However, researchers are often hampered by data availability to test their models and to accurately determine water residence time. In this study, long dataset of stable environmental isotopes was used, and water residence time was determined using different approaches with varying degree of complexities. Suitability and limitation of each approach were addressed. Further, this study shows that environmental isotopes are useful tools in climate change studies.