Anomalous rainfall trends in the North-Western Indian Himalayan Region (NW-IHR)

The North-Western Indian Himalayan Region (NW-IHR) is the source of some of India’s major rivers and hosts a few of the highest mountain peaks in the world. The region is also a major source of water for the population living in the plains. We study the rainfall trends, magnitudes, and seasonal and annual variations in the NW-IHR during the last 120 years (1901–2020). The temporal trends in rainfall are estimated using the Mann-Kendall Test (MKT) and Modified Mann-Kendall Test (MMKT) at 10%, 5%, and 1% significance levels. The ACC at lag-1 was calculated and tested at 5% significance level for the MMKT. The magnitude of the seasonal and annual rainfall was calculated using Sen’s Slope (SS), Simple Linear Regression (SLR) , Innovative Trend Analysis (ITA) , and Spearman ’ s Rho (SR). The variability of seasonal and annual rainfalls was studied using the Coefficient of Variation (CV) . The results of our analysis revealed both increasing and decreasing trends at various levels of significance during seasonal and annual rainfalls. The majority of the districts in the northern region showed increasing trends, while the districts in the southern region showed decreasing trends. CV was higher for seasonal rainfalls as compared to annual rainfalls. Our analysis of trends and variability will help the local stakeholders for efficient planning and understand the risk and vulnerability of the region at large.