This book presents a comprehensive guide on the applications of isotopic methods in hydrology. It covers key isotopic techniques for tracing and analysing water in various hydrological systems. The inclusion of studies from different terrains, including mountainous, arid, coastal, and wetland regions, demonstrates the practical applications of these methods. The book covers applications of water isotopes in freshwater spring hydrology, groundwater investigations in arid regions across desertic Rajasthan, and evolving spring rejuvenation studies across the Himalaya, including Nepal, Jammu, and Kashmir. The book also includes methodology-focused chapters that discuss partitioning evapotranspiration using oxygen and hydrogen isotopes, highlighting key methodological challenges and practical insights. The volume also presents integrated numerical and isotope-based approaches for submarine groundwater discharge studies. It is designed for graduate students, researchers, and practitioners seeking to understand the role of isotopes in hydrology and water resource management.

Dr. Gopal Krishan is a Scientist-E at the National Institute of Hydrology (NIH), Roorkee, India. He previously served as a Researcher on the Indo-Gangetic Basin Groundwater Resilience Project at the British Geological Survey (BGS), United Kingdom (2014–2015), and at the Indian Institute of Remote Sensing (IIRS), ISRO (2006–2009). With over 25 years of research experience, he has extensive expertise in hydrological investigations, groundwater and surface water assessments, project management, and field-based hydrogeological studies, with specialization in isotope hydrology, hydrogeochemistry, groundwater recharge, groundwater–surface water interactions, and water quality. He has successfully supervised five Ph.D. scholars, 39 Master's dissertations, one CV Raman Fellow (Ghana), and one DAAD Fellow (Germany). Dr. Krishan has published more than 100 papers in peer-reviewed international journals, authored three books, contributed over 15 book chapters, prepared numerous national and international technical reports, and serves on the editorial boards of reputed scientific journals. His contributions to water resources research have been recognized through several prestigious honours, including the Jal Shakti Hackathon Award (2025), election as a Fellow of the Association of Global Groundwater Scientists (2025), and recognition as an American Water Resources Association (AWRA) Member Spotlight (2020). He is working in collaborations with BGS, UK; HTWD, Germany; IAEA, Vienna; University of Paris, Saclay; Western Sydney University, Australia.

Praveen Kumar is currently a PhD scholar in the Department of Earth Sciences, Indian Institute of Technology, Roorkee (India). His research primarily focuses on mountainous hydrogeology, specifically examining geochemical and geophysical techniques for springshed rejuvenation and management in the Himalayan region.

Dr. Suhas Damodar Khobragade completed his B. Tech (Ag. Engg). from PKV, Akola (Maharashtra) in 1989, M. Tech.  (Water Res. Dev. & Mgt.) from IIT, Kharagpur in 1992 and Ph.D. from IIT, Roorkee in 2010. He has more than 33 years of research experience. He is presently working as Scientist-G and Head, Hydrological Investigations Division at the National Institute of Hydrology, Roorkee. India. His major areas of research work include Wetland & Lake Conservation, Hydrology of wetlands and lakes including Himalayan lakes & Urban Lakes, Water Balance of lakes, Erosion and Sedimentation studies for lakes, Hydrology of upper Ganga river basin, Isotope applications in lake & wetland studies, spring studies & other hydrological studies. The major lakes and wetlands studied by him include Sukhna lake, Chandigarh; Pichhola lake, Udaipur; Nainital Lake, Uttarakhand; Ramgarh Tal, Gorakhapur; Rewalsar Lake, Himachal; Khijadiya wetland, Gujrat,  Gosabara wetlands, Gujrat,  Bhimtal & Naukuchiyatal lakes, Nainital; etc.  Presently a project on Wular lake, Kashmir is being undertaken by him. Dr. Khobragade has also undergone trainings abroad which include 4 months training on Lake Hydrology at Lund University, Sweden during 1997-98 and 2 months training on Integrated Lake Basin Management (ILBM) at ILEC, Japan during 2013. He has more than 70 publications to his credit in various international journals, national journals, international conferences and national conferences. He also has two edited books to his credits. He has also contributed significantly to a number of BIS standards. He has worked in more than 20 sponsored and consultancy projects and has prepared more than 30 technical reports. He has delivered more than 50 lectures on various training courses and has also guided more than 10 M.Tech/Msc/Phd theses. He has successfully organized a number of International Conferences, National Conferences and Training Courses and workshops. He has been involved in various techno-administrative responsibilities of the Institute and is also an expert member for some state government technical committees.