An Analysis of Precipitation Patterns in the Major Cities of Nepal

Abstract

Climate change has significantly altered precipitation dynamics, increasing the frequency and intensity of extreme rainfall events. However, infrastructure design practices in Nepal still largely depend on stationary assumptions based on historical rainfall records, creating a critical gap between evolving climatic conditions and existing engineering standards. This study evaluates temporal changes in precipitation patterns across eleven major cities of Nepal, representing the Mountain, Hilly, and Terai regions over the period 1981–2024. The objectives were to develop precipitation inventory datasets, estimate 10-year return period storm intensities, and assess variations in design rainfall values over time. Daily rainfall data obtained from the NASA POWER database were analyzed using the Annual Maximum Series (AMS) approach. The dataset was divided into two equal periods: 1981–2002 and 2003–2024. Return periods were estimated using the Weibull plotting position formula, while 10-year storm intensities were derived through logarithmic and linear trendline modeling. Results indicate that 9 of the 11 cities experienced increased rainfall intensity during the recent period. Pokhara exhibited the highest increase (92.834%), followed by Jomsom (82.606%) and Jumla (50.245%). The findings confirm climatic non-stationarity across Nepal and highlight the urgent need to revise rainfall standards and update engineering design codes for climate-resilient infrastructure planning.