Observed Trends and Spatial Distribution in Daily Precipitation Indices of Extremes over the Narayani River Basin, Central Nepal

Dipendra Lamichhane¹, Binod Dawadi^{1, 2,} , Ram Hari Acharya¹, Saroj Pudasainee¹ and Ishwar Kumar Shrestha³

¹Central Department of Hydrology and Meteorology, Tribhuvan University, Kathmandu, Nepal

²Kathmandu Center for Research and Education, Chinese Academy of Sciences Tribhuvan University, Kathmandu, Nepal

³Department of Statistics, Amrit Campus, Tribhuvan University, Kathmandu, Nepal

Cite this paper:
Dipendra Lamichhane, Binod Dawadi, Ram Hari Acharya, Saroj Pudasainee and Ishwar Kumar Shrestha. Observed Trends and Spatial Distribution in Daily Precipitation Indices of Extremes over the Narayani River Basin, Central Nepal. Applied Ecology and Environmental Sciences. 2020; 8(3):106-118. doi: 10.12691/aees-8-3-6

Abstract

Climate change is 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 different scientific tools and programs were used to check the data quality and homogeneity. 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 weakeing 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).

Keywords:
climate change Narayani river basin ClimPACT2 ET-SCI precipitation indices

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