Long Term Historic Changes of Precipitation and Aridity Index over an Indian River Basin

In the present study, long term historic changes in precipitation and aridity index (AI) was examined for the period of years 1901 to 2013 at 21 hydro-meteorological stations over Betwa River Basin, part of Uttar Pradesh and Madhya Pradesh states of Central India. Modified Mann-Kendall test was applied for detecting the long term trend and to deal with the condition of serial correlation in time series of precipitation and aridity index. Further, Sen's slope estimator was employed for estimation of slope. AI was calculated for various seasons using formula recommended by United Nations Environment Program. The results revealed that some of the hydro-meteorological stations exhibited increasing trend of precipitation and AI during pre-monsoon season. During monsoon season two stations (Banda and Narsinghpur) exhibited decreasing trend of AI with slope of -2.45 x10(-3) and -2.74 x10(-3), respectively due to increase in potential evapo-transpiration (PET), however, no significant trend was observed in precipitation. During post-monsoon season, no significant trend in precipitation as well as AI was observed. During winter season, only one station (Bhopal) exhibited increasing trend with slope of 0.05 mm/year and 11.84 x10(-5) for precipitation and AI, respectively. On yearly basis, only one stations (Banda) exhibited decreasing trend of precipitation with slope of -1.25 mm/year and two stations (Banda and Hamirpur) exhibited decreasing trend of AI with slope of -55.9 x10(-5) and -60.35 x10(-5), respectively. The results of this study is useful for understanding the behavior of drought conditions in the study area.