*Corresponding author: kumar.nanthu@gmail.com
Identification of temporal variation of rainfall trends provides useful information for sustainable planning and management of water resources in a river basin particularly during flood and drought periods. The present study was conducted to determine trends in the annual and seasonal total rainfall over Parambikulam Aliyar sub basin of Tamil Nadu using 30 years (1982–2012) monthly rainfall data at eight rain-gauge stations. The procedure is based on the nonparametric Mann-Kendall test for the trend and the nonparametric Sen's method for the magnitude of the trend. The maximum increase in rainfall was found at Chinnakallar with an annual rainfall of 90.51 mm/year and the maximum reduction in rainfall of -8.60 mm/year was found at Topslip during South West monsoon. Significant positive trend were observed at Weaverly station during North East monsoon rainfall series and significant negative trend has been noticed in the South West monsoon of Topslip.
Positive trends were observed in most of the rain-gauge stations for all rainfall series except South West monsoon season. Rainfall trends determined by Mann-Kendall test reflected in the linear regression analysis.
Rainfall trend, Mann-Kendall test, Sen's slope estimator, Regression
