Rainfall variability in Kathmandu Valley, Nepal

Abstract

This study examines rainfall variability in the Kathmandu Valley from 1971 to 2023, utilizing daily rainfall data from 19 weather stations. The annual, monthly, and seasonal means were determined. The results indicate that July is the wettest month, while November is the driest. Monsoon is the primary source of rainfall, accounting for 78.79%, followed by pre-monsoon (13.53%), post-monsoon (4.62%), and winter (3.06%). Overall average annual rainfall has fallen, including during the monsoon, post-monsoon, and winter seasons, with just a tiny increase during the pre-monsoon season. The spatial investigation found that the northern valley receives more rainfall, particularly in Sundarijal (Mulkharka), except during the post-monsoon season, when Godavari and Changu Narayan receive more. Middle elevations receive more rainfall than lower elevations. Kathmandu's rainfall has decreased in recent decades. The study reveals that the Kathmandu Valley experiences high rainfall variability, with large monsoon rains triggering flooding and extended dry spells leading to water scarcity. The trend study shows that yearly, and seasonal rainfall are decreasing. This emphasizes the importance of good water management measures for dealing with monsoon flooding and year-round water scarcity.