Assessment of variability in monthly, seasonal and annual rainfall received during 140 years at Ananthapuramu district of Andhra Pradesh

A detailed assessment of climate change has been done by considering the historical rainfall data of Ananthapuramu in India for 140 years from 1877 to 2016. The input data comprised of monthly, seasonal (CWP, HWP, South-West, North-East) and annual rainfall received in each year. Based on the study, a decreasing trend in rainfall in different months, seasons and annual rainfall over years was observed. Among the 4 seasons, CWP had minimum deviation of rainfall compared to the historical average rainfall. The mean decennial rainfall during the 4 seasons of CWP, HWP, SWM and NEM was about 550.0 mm (with CV of 4.7%), skewness of-0.4 and kurtosis of 0.9 during the 140-year study. The rainfall of SWM and NEM, apart from annual rainfall had a lower variation compared to the rainfall of CWP and HWP. A decadal analysis of 10-year and 30-year mean rainfall along with its variability was made by considering the discontinuous periods. The annual trends were compared with 2-year, 3-year and 5-year moving averages and standardized trends, apart from assessing the variability of rainfall. The moving average models provided a consistent estimate of rainfall, after reducing the variability over years. Based on the regression analysis, the monthly, seasonal and annual rainfall were found to be predictable with minimum prediction error. The seasonal rainfall was better predictable compared to the monthly and annual rainfall over years. Based on the changes occurring in the rainfall patterns, there is a need for adoption of suitable soil and water conservation practices apart from growing efficient crops for sustaining the productivity and monetary returns and improvement of livelihood of farmers’ under arid Alfisols at Ananthapuramu.