Abstract
Global climate change has local implications. Focusing on datasets from the topographically-challenging Karnali river basin in Western Nepal, this research provides an overview of hydro-climatic parameters that have been observed during 1981–2012. The spatial and temporal variability of temperature and precipitation were analyzed in the basin considering the seven available climate stations and 20 precipitation stations distributed in the basin. The non-parametric Mann–Kendall test and Sen’s method were used to study the trends in climate data. Results show that the average precipitation in the basin is heterogeneous, and more of the stations trend are decreasing. The precipitation shows decreasing trend by 4.91 mm/year, i.e., around 10% on average. Though the increasing trends were observed in both minimum and maximum temperature, maximum temperature trend is higher than the minimum temperature and the maximum temperature trend during the pre-monsoon season is significantly higher (0.08 °C/year). River discharge and precipitation observations were analyzed to understand the rainfall-runoff relationship. The peak discharge (August) is found to be a month late than the peak precipitation (July) over the basin. Although the annual precipitation in most of the stations shows a decreasing trend, there is constant river discharge during the period 1981–2010.
Highlights
Global climate change is unequivocal and it is acting locally upon us [1]
The summer monsoon which originates from the Indian Ocean [41] is the main cause of precipitation in Nepal and as the Karnali River Basin (KRB) lies in the western part of Nepal its influence is weaker than in eastern part of Nepal [42]
The distribution of the monthly average rainfall in the KRB (Figure 3) shows that highest precipitation occurs in July (377 mm) and lowest in November (10 mm which is less than 1% of total precipitation)
Summary
Global climate change is unequivocal and it is acting locally upon us [1]. Studies show that the Earth’s surface has been successively getting warmer [2] and available observations suggest that the Himalayan region, which is more sensitive than other land surfaces of the same latitude [1,3], is experiencing warming [4] with greater magnitude than the global average [5,6]. The Himalayan region data indicates a statistically significant decreasing trend in summer precipitation [11,12,13] and the rate of increasing temperature is projected to be two to three times higher than that recorded during the 20th century [14]. This research has been focused in the western part of Nepal that will contribute to a better interpretation of the hydro-climatic (temperature, precipitation, river discharge) status, which helps to understand the changes in the climate system in this region and, at the same time, it will contribute to generating climate information in this part of the data-sparse
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