An advanced approach for Assessment of Spatiotemporal Variation in Rainfall and its Impact on Stream Flow Discharge in Chaliyar River Basin of Kerala

Understanding the precise spatiotemporal movements of rainfall and its relationship with streamflow moment is crucial for effective water resource management in the Western Ghats region, particularly in the Chaliyar basin where extreme events have increased, resulting in repetitive disasters. To investigate the impact of rainfall variations on stream flow discharge in the basin, it is necessary to conduct a long-term analysis of rainfall and stream discharge data. To conduct this study, daily rainfall and stream discharge data were collected from three rain gauging and one streamflow gauging station over a period of 30 years. Data were subjected to analysis using different statistical methods such as the Modified Mann-Kendall test, Innovative Polygonal Trend Analysis (IPTA), and cross correlation analysis. The results revealed significant differences in rainfall and subsequent discharge data, with September rainfall showing a significant trend across the basin. Extreme events such as consecutive wet days and 20mm/day rainfall exhibited an increasing trend in all stations, and IPTA results indicated a significant shift in successive transition of rainfall in the South West Monsoon months. Stream flow analysis indicated an increasing trend in stream flow during September, with discharge higher than normal during this month. The cross-correlation analysis showed a delay of approximately 13, 8, and 11 days, respectively, for the rainfall to reach the stream gauge at these stations during September. These findings highlight the need to re-plan effective water resource management strategies in the Chaliyar river basin, taking into account the delay between rainfall events and the corresponding rise in stream-flow.