The Impact of Climate Change on Rainfall Variability: A Study in Central Himalayas

The impact of anthropogenic activities on the earth atmosphere and its systems has been an area of extensive research and engaging the attention of planners, governments, and politicians worldwide. The countries across the world are engaged in working out the impacts and associated vulnerabilities to the projected climate change. In India, the meteorological records indicate rise in the mean annual surface air temperature by 0.4 °C with not much variations in absolute rainfall. However, the rates of change in temperatures and precipitation have been found to be varying across the region. The intensity and frequency of heavy precipitation events have increased in the last 50 years. No change in the total quantity of rainfall is expected, however, the spatial pattern of the rainfall is likely to change, with rise in number and intensity of extreme rainfall events. The continuous warming and resulting change in rainfall pattern over different regions of Indian may adversely impact the natural resources on which majority of the population is dependent. Thus there is an ever increasing recognition of the need for micro and macro level assessments for greater understanding about the impact and implication of the current climate variability especially in eco-sensitive Himalayan region, where such studies are limited due to lack of adequate observational sites and related data. This study investigates the rainfall variability trends on annual and seasonal scales in the central Himalayan region. Eight observational sites at Almora, Nainital, Ranikhet, HawalBagh, Mukteshwar, Mukhim, Dehradun, and Mussoorie situated at different altitude in the central Himalaya region are considered for the study. These sites are situated within the altitude range of 682–2311 m. Statistical tools such as Mann–Kendall test, Sens’s estimator of slope method (nonparametric) and regression (parametric), have been applied to analyze the rainfall variability trends at these observational sites. The significance of these trends has been tested at the 95% confidence level. The results indicate that there is decreasing trend at all the stations annually, however; only two stations show significantly decreasing trends at 95% confidence level. At seasonal scale, monsoon rainfall indicates decreasing trends at most of the stations in the region, whereas winter rainfall also shows the similar patterns. These temporal and spatial patterns of rainfall variability in central Himalayas may provide useful insights for the long-term planning and management of water resources and also useful for climatic studies in this region.