Most recent edition is (check Khanna Publishers). Older editions (3rd/4th) have fewer chapters on GIS/remote sensing but cover 90% of the core syllabus identically. An older used copy is fine for most exams.
Dr. S.K. Garg is a revered author in the Indian engineering education circuit, known for his simple, exam-oriented writing style. First published decades ago, has been updated through numerous editions (often 25th or 26th edition) to include modern techniques like GIS in hydrology and remote sensing. Most recent edition is (check Khanna Publishers)
Searching for a PDF download of Hydrology and Water Resources Engineering known for his simple
: S.K. Garg introduces techniques for computing runoff from rainfall data, which is critical for designing water management systems. Most recent edition is (check Khanna Publishers)