This chapter assesses long-term rainfall and runoff records to identify trends and step changes. Multiple statistical tests are applied: the Mann-Kendall and modified Mann-Kendall tests for trend detection, and Pettitt’s test, Sequential Mann-Kendall test, Buishand’s U test, Buishand’s range test, and the Standard Normal Homogeneity Test for step-change analysis. The results indicate no significant trends or breakpoints in basin-average rainfall series, with only a few localized grid-specific rainfall series exhibiting increasing trends. In contrast, significant breakpoints in streamflow are detected in 2001 and 2008, along with statistically significant decreasing trends in both monsoon and annual runoff series. In other words, rainfall remains largely stationary, while runoff exhibits a declining tendency. This decoupling between rainfall and runoff suggests that non-climatic factors, such as land-use and land-cover change, are likely driving the observed reduction in streamflow. By establishing this hydrological baseline, the chapter fulfills the first research objective and provides a foundation for the impact analysis presented in the subsequent chapter.