Variability and trends of rainfall using non-parametric approaches: A case study of semi-arid area

Abstract

The analysis of variability and trends of rainfall can be used to assist better decision for climate risk and agricultural water management. This study makes an attempt to evaluate the trend and variability of annual, seasonal and monthly rainfall of 19 stations of Ajmer district, Rajasthan based on 44 year’s monthly rainfall data (1973-2016). Non-parametric Mann-Kendall (MK), Modified Mann-Kendall (mMK) and Spearman’s rho (SR) tests were used to achieve if there was an increasing or decreasing trend in the time series and the Sen’s slope (Q) estimator was applied to identify the quantity of the trend. From the results, it was found that annual and monsoon rainfall both showed an increasing trend at three stations, located in the central part and a decreasing trend at two stations, located in the north-western and south-western part of the study area. The magnitude of maximum increasing trends in both annual and monsoon rainfall was observed at Goela (Q=+10.17 mm/year and+9.50 mm/year) while Jawaja (Q = - 6.76 mm/year and -5.21 mm/year) appeared with the maximum decreasing trends. On a monthly scale February showed an increasing trend at maximum number of stations (seven) and July showed a decreasing trend at maximum number of stations (seven). The information gathered from our study will help in future to estimate hydraulic procedures as well as to make sustainable water resource planning and management in this region.