Abstract
This paper analyses the climate projections over the Koshi river basin obtained by applying the delta method to eight CMIP5 GCMs for the RCP4.5 and RCP8.5 scenarios. The GCMs were selected to cover the full envelope of possible future ranges from dry and cold to wet and warm projections. The selected coarse resolution GCM outputs were statistically downscaled to the resolution of the historical climate datasets. The scenarios were developed based on the anomaly between the present reference period (1961-1990) and the future period (2021-2050) to generate transient climate change scenarios for the eight GCMs. The analyses were carried out for the whole basin and three physiographic zones: the trans-Himalaya, high-Himalaya and middle mountains, and southern plains. Future projections show a 14% increase in rainfall during the summer monsoon season by 2050. The increase in rainfall is higher over the mountains than the plains. The meagre amount of rainfall in the winter season is projected to further decrease over both the mountain and southern plains areas of the basin for both RCPs. The basin is likely to experience warming throughout the year, although the increase in winter is likely to be higher. The highest increase in temperature is projected to be over the high Himalayan and middle mountain area, with lower increases over the trans-Himalayan and southern plains areas.
Highlights
Mountain regions are sensitive to climate change and variability [1]
In order to analyze the different changes that are likely to occur in different parts of the basin, it was divided into three physiographic zones: the trans-Himalayan area to the north; the high Himalayan and middle mountains area in the center, and the low lying plains area to the south
The Koshi basin is heavily influenced by the monsoon; about 80% of annual total rainfall falls in the monsoon season (June to September). the winter rainfall (December, January, February) is quite meagre, it is very important for the winter crops
Summary
Mountain regions are sensitive to climate change and variability [1]. The Himalayan mountains are. The basin has a high potential for investment in hydropower development, and in irrigation in the downstream areas It contains important ecosystems and protected areas that provide a wide range of biodiversity and ecosystem services, which sustain the livelihoods of the local communities, as well as contributing important services at regional and global scale. In order to analyze the different changes that are likely to occur in different parts of the basin, it was divided into three physiographic zones: the trans-Himalayan area to the north (mainly the Tibetan plateau area in China); the high Himalayan and middle mountains area in the center (mostly in Nepal, hereafter referred to as the “middle mountains”), and the low lying plains area to the south (in Nepal and India)
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