Observed Trends and Spatial Distribution in Daily Precipitation Indices of Extremes over the Narayani Basin, Nepal
Date
2020
Authors
Journal Title
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Publisher
Department of Hydrology and Meteorology
Abstract
Climate change is one of the biggest environmental challenge that plays out through changing
intensity, duration, and frequency of extreme events. To fulfill the research gap in understanding
and quantifying the recent changes in precipitation extremes over the Narayani river basin of
central Nepal, the long-term daily precipitation data from 1980 to 2018 were run in ClimPACT2
an R software package to calculate ET-SCI extreme precipitation indices. In this study physically
relevant 14indices obtained from 23 stations were examined for their spatial and temporal
variation. Before the calculation of indices data quality and homogeneity test was performed.
The results suggest that the variations of extreme indices throughout the study area are quite
different from that of seasonal and annual patterns to some extent. The monsoonal precipitation
was mostly concentrated in the central part of the basin within the Middle Mountain region
(Lumle and its surroundings). Especially the lowlands (Terai and Siwaliks) and including some
parts of middle mountains the precipitation intensity-based indices like as, percentile indices
(R95p) and absolute indices (RX1day, RX3day, RX5day) were in the increasing trends, but the
frequency of precipitation like threshold indices (R1mm, R10mm, R20mm) along with the
duration of precipitation seemed to be decreasing. This implies that the lowlands regions
bringing about rainfall related hazards like floods and soil degradation with inundation and may
cause possible impact on agriculture and livelihood due to intense rainfall and prolongation of
dry spells with the weakening of rainfall duration (days/year). However, the light to moderate
precipitation and associated days over the high altitude and that could be the possible cause of
landslides. This study also highlights the suggestion that there may be a possible impact on
agriculture facilities, food security, and water scarcity in the eastern part of the basin due to the
significant decreasing trend of annual total wet days precipitation (PRCPTOT)
Description
Keywords
Climate change, ClimPACT2, ET-SCI precipitation indices, Narayani river basin