Long-Term Rainfall Trend Variability Analysis for Rampur Watershed: A Case Study of Mahanadi River Basin

Abstract

Precipitation is one of the pronounced indicators of climate change. The behavior of historical rainfall pattern becomes necessary to study the climate change, because of the complex phenomenon of the rainfall variability. The study of spatial and temporal variability of precipitation in the Rampur watershed of Mahanadi river basin has been carried out in this paper. Mann– Kendall (MK) and modified Mann–Kendall (MMK) tests have been used to determine the possible trends of daily rainfall data for the period 1983–2015. 274Further, the Sen slope estimator (SSE) has been used to assess the magnitude of the whole time series. Arc-Map 10.1 software has been used to determine the spatial patterns of the trends over the whole watershed by applying the inverse distance weighting (IDW) interpolation technique. Further, the MK and MMK tests have been used to identify the possible trend analysis of the entire time series with 95% level of significance. The premonsoon season for both MK and MMK tests gave a positive significant trend for only SW 1. In monthly trends (using MK and MMK), 86% of the values has been indicated by a negative trend (either statistically significant or nonsignificant) and the month of September indicated a positive trend for all the subwatersheds (SWS). In MMK statistics, a positive significant trend has been observed in the month of August in only SW 1. The magnitude in the postmonsoon season gave all negative values for all the SWS. In monthly precipitation data, the months January, November, and December showed no trend values for all the 9 SWS. The months September and June showed all positive and negative values, respectively. The highest value of the coefficient of variation has been detected in postmonsoon season (146%) and the lowest has been detected in monsoon season (19.93%).