Extreme precipitation is one of the major challenges for mountainous regions imposing threats to the sustenance of the inhabitants. The total precipitation (TP), soil–water (Sm), total evaporation (TE), and total runoff (TR) variations in a microclimatic region, particularly one with challenging topography, are key components of the hydrometeorological water budget. This study is an assessment of the water budget of the Alaknanda River basin (using ERA5-land reanalysis datasets), which is a major tributary of the Ganga River feeding to the most populated region of India. The temporal trends of total precipitation for the study period 1981–2020 is found negative over north-western part of Alaknanda River basin, however southern part is positive (similar for total runoff) whereas, the opposite is found for the total evaporation and soil–water. The change in storage (∆S) is calculated by subtracting the output from the input. Thereafter, the storage has declining trend over entire basin (except northern-most region) with range value − 20 to − 60 mm/year. Furthermore, the precipitation extremes, along with number of consecutive dry days (CDD) is found to be rising through lower section of the basin. The strong (negative/positive) correlation (spatial/temporal) between extreme precipitation and storage is pragmatic.