Asian Journal of Geographical Research

Precipitation is a significant climatic variable as it changes in intensity and amount, affecting the occurrence of hydrological risks such as floods and drought. The rainfall variability assessment plays a vital role by applying the Precipitation Concentration Index (PCI), which accurately forecasts rainfall patterns, floods, and droughts across the regions. Therefore, the objective set for the current work is to assess the concentration of rainfall by employing the Precipitation Concentration Index (PCI) and the Standardized Rainfall Anomaly Index (SRAI). The monthly rainfall data of 76 years (1950-2025) were utilized for the Igatpuri, Aswali, and Wasali rain gauge stations over the Darna River Basin. Similarly, the Mann–Kendall (MK) trend test and Sen’s Slope Estimator (SSE) were developed to assess the trend in the precipitation concentration based on PCI. The PCI was computed at the annual and seasonal levels using annual and seasonal equations for the evaluation of the concentration of precipitation; similarly, SRAI was used to examine annual precipitation data to determine the number of dry and wet years over time. The spatial distribution of the PCI map was prepared by using the inverse distance weighted (IDW) technique in the GIS environment. The results reveal that all stations' annual average PCI values are >20, indicating that the annual rainfall distribution is strongly irregular. The seasonal breakdown shows that the actual rainy season (Monsoon) has a moderate, regular distribution, although the annual PCI signifying strong irregularity with high concentration. No statistically significant trend observed at Igatpuri throughout the period, whereas a highly significant trend was noted throughout the period at Aswali rain guage station. Annually Aswali station shows the highest (Z=12.03) PCI trend values. The notable severe positive anomaly that peaked at Aswali is 7.71 in 2021, followed by SRAI 3.37 in the year 1995, which interprets the extremely wet (flood) years. The remarkable negative SRAI values at Igatpuri station are -2.24 (1962), -1.97 (1965), and -1.90 (2024 and 2025), that indicates the extremely severe dry years associated with drought. The study is important to show the water potential of the study area. It is also essential to recommend to water managers, farmers, policymakers, and decision-makers to minimize risks and plan future water utilization, in addition to providing a scientific contribution for researchers.