Precipitation and extremes in a changing climate: A case study of Gandaki basin

Extremes represent an important aspect of the climatology of a region are important for water-related disaster prevention and mitigation as well as water resource management. Climate variability itself makes the task hard, which is further execrated by climate change. Using observed daily precipitation dataset from 61 meteorological stations in the Gandaki basin from 1956-2013 trends in extreme precipitation is analyzed. Only stations having data more than 30 years are used in this study. Mann-Kendall (MK) and Sen's slope tests were applied to assess trends of extreme rainfall series.

9 stations have a significant decreasing trend in extremes and annual time series. The direction of the trend is the same although the stations in both the series are not the same. 5 stations have a significant increasing trend in extremes and annual time series. The stations are not the same in both series but stations have the same trend in both series.

8 stations have a decreasing trend in extremes but increasing annual precipitation whereas 5 stations have increasing extremes and decreasing annual precipitation. Overall 22 stations have a decreasing trend and 39 have an increasing trend in extremes. Similarly, 22 stations have a decreasing trend and 39 have an increasing trend in annual time series. The decreasing trend is more pronounced in stations having higher elevations (3000 m above). Stations at lower and middle elevations have a more pronounced increasing trend. Overall precipitation has increased in the Gandaki basin during the study period.