Analyses of rainfall variability, trend, and change-point detection over the Upper Krishna Basin, India

The assessment of rainfall change points and trends is an essential component in comprehending the effects of climate change on water resources, which is necessary for planning and managing floods and droughts in the region. The current study aims to investigate the long-term variability, trends, and change points in monthly, monsoon, and annual rainfall data from 1901 to 2020 in the Upper Krishna Basin (UKB). The analysis of the coefficient of variation (CV) revealed a 23% variation in monsoon rainfall and a 22% variation in annual rainfall, suggesting a moderate level of rainfall variability at the basin scale. The analysis of rainfall trends has incorporated the Mann–Kendall (MK) test, Sen’s slope estimator (SSE), percentage change techniques, and Pettitt’s test for the detection of change points. The MK-test indicated a notable reduction in monsoon (Z = −2.75) and annual (Z = −2.43) rainfall in the UKB. This downward trend was linked to a significant decline in rainfall observed during June (Z = −1.70) and July (Z = −3.54). A reduction of about 41% in rainfall was recorded for July, which is typically regarded as the wettest month. Consequently, the monsoon (annual) rainfall exhibited a decrease of about 22% (18%) across the UKB from 1901 to 2020. Pettitt’s test indicated that the year 1998 marked a significant shift (negative) in the trends of monsoon and annual rainfall across the UKB.