Trends in Extreme Precipitation Indices over Bhutan

Abstract

With the changing climate, the frequency and intensity of extreme precipitation events are increasing. Climate change is projected to increase both mean and extreme precipitation. Socio-economic damages can be immense and require a difficult recovery, especially for developing countries such as Bhutan. Furthermore, changing precipitation patterns affect land productivity and water availability. The Experts Team on Climate Change Detection Indices (ETCCDI) is used to find the changes associated with extreme precipitation in Bhutan. The study of extreme precipitation is important for Bhutan, whose economy is dependent on agriculture and hydropower. Even for a small country, there were varying patterns of precipitation in different districts. Deothang district received less frequent and more intense rainfall, while Haa, Bumthang, Trashiyangtse, and Chukha received weak but persistent rainfall. Mann–Kendall trends revealed a drier climate for two districts, Dagana and Trashiyangtse, and a wetter climate for the Mongar district. Modeling of the extreme rainfall with extreme value theory (EVT) revealed that the generalized extreme value (GEV) distribution by their T = 50-year return value, indicating an increasing value of annual maximums for all stations. This study is the first of its kind for Bhutan, and the findings can be used for decision support and the planning of appropriate adaptation strategies for hydro-meteorological disasters, hydropower, and agriculture sectors in Bhutan.

Keywords

• extreme precipitation
• ETCCDI
• extreme value theorem
• return levels
• Bhutan