Cosmos: A Journal of Geography

Annual and seasonal spatio-temporal analysis of rainfall gridded data (1950-2023) over Darna River Basin, India

The present paper attempts to analyse the rainfall distribution, variability, and trends in annual and seasonal scales over the DRB, India. The high-resolution (0.25° x 0.25°) daily gridded datasets for 74 years (1950-2023) have been procured from the India Meteorological Department (IMD). To assess the basic trends of the rainfall data, statistical techniques such as standard deviation (SD), non-parametric method Mann–Kendall (MK) trend test, and Sen’s Slope Estimator (SSE) have been performed for annual and seasonal scales. In addition to understanding the station-wise temporal rainfall change (%), and departure from the mean of the annual and seasonal rainfall data has been computed for further analysis. Lastly, all thematic maps have been prepared by using the inverse distance weighted (IDW) technique in the GIS environment. The study revealed that the CV in the case of the winter season was computed the highest, 521% at Wasali, followed by 400 % in pre-monsoon at Asvali, indicating high variability of rainfall. The annual trend shows that a significant increasing trend was observed towards the east part at Asvali (Z=3.35) and Wasali (Z=2.74) rain gauge stations than the west. Likewise, a significant increasing trend was noted (at a 99% significance level) in the monsoon season (June-September) at Asvali (Z=3.30) and Wasali (Z=3.02) as compared to the Igatpuri station. During the pre-monsoon season remarkably significant decreasing trend was noted at Wasali (Z= -2.39), whereas no trend was noted in the post-monsoon season at Wasali. It also figured out that the Asvali station recorded rainfall departure from the mean at the annual scale was highest, +221.5% (2005), followed by +150.3% (2008). The approach adopted in this paper will be greatly advantageous for flood and drought risk management and could be helpful for policymakers associated with sustainable water resource and agriculture management. Keywords: gridded data; trend and magnitude; flood; drought; darna river basin