ABSTRACT
The Tapi basin (area ≈ 65,145 km2), in western central India, is one amongst the climatically sensitive river basins in India. The Tapi basin exhibits three distinct climatic regimes as per Köppen–Geiger climate classification, wherein around 37.7% of the basin area experiences a semi-arid climate. The normal annual rainfall in the Tapi basin varies from 540.4–1795.4 mm, with an average of 32.0–66.6 rainy days. The trends in hydroclimatic indices within the basin are estimated using the Modified Mann Kendall (MMK) test. The trends in total and extreme rainfall exhibit heterogeneity across the Upper and Middle Tapi basins, whereas uniformly increasing trends are observed over the coastal plains of the Lower Tapi basin. The rainy days are found to increase across Middle and Lower Tapi basins. On the other hand, the annual runoff has been found to decrease uniformly across the Tapi basin, except in the upper reaches of the Tapi River. The extreme streamflow shows an increasing trend in the Upper Tapi basin (except at the Yerli station), while mostly a decreasing trend is observed in the Middle and Lower Tapi basins. Thus, the Tapi basin exhibits sensitivity to both drought and flood occurrences, wherein the coastal plains of the Lower Tapi basin are flood prone, while the river plains of the Middle Tapi basin are susceptible to droughts.
