Regional climate trends and topographic influence over the Western Ghat catchments of India

This study investigates the role of elevation stratification and climate change on the hydrology of Western Ghat catchments during the period from 1951 to 2013 using gridded data. The trend analysis of rainfall and temperature was conducted using the Mann–Kendall trend test, and the hydrological modelling of the rivers was conducted using the Soil and Water Assessment Tool (SWAT) model. To characterize the spatial distribution of rainfall and streamflow based on elevation stratification, contemporary rainfall zones were delineated and the response of each zone was evaluated. The results indicated that the maximum rainfall occurs at certain distance on the windward side from the crest of the Western Ghats. On the leeward side (eastern plateau), the rainfall is maximum at crest (Western Ghats) and decreases with distance. The rivers in the southern portion of the Western Ghats of India were highly vulnerable to changing climate followed by the central portion. The annual and monsoon rainfall in the southern river decreased at 0.43 and 0.30 decade−1 (1 significance level), respectively. The summer rainfall in the river of the central portion (Netravathi River) decreased at 0.44 decade−1. The annual air temperature of the southern river catchment (Vamanapuram) increased at the rate of 0.12 °C decade−1 (at 0.1 significance level), and the air temperature of the central rivers increased at the rate of 0.09, 0.08, and 0.07 °C (0.1 significance level), respectively. The streamflow response of the southern and central rivers was discernible as the monsoon flow decreased at 37 decade−1 (0.1 significance level) in the southern river and 10 decade−1 (5 significance level) in the central river. Interestingly, the pristine Aghanashini River demonstrated resilience to climate change with an increase in annual rainfall and streamflow at 115 mm decade−1 (5 significance level) and 0.71 Mm3 decade−1 (0.1 significance level), respectively