Spatio-Temporal Variability and Trend Analysis of Long-Term Rainfall in Parbati River Basin, Rajasthan

The examination of rainfall variability and trends can provide valuable insights for climate risk assessment and agricultural water management. This study aims to assess the spatial and temporal variability and trends in annual, seasonal, and monthly rainfall of Parbati River basin, Rajasthan, using 43-year (1981-2023) data. The original and modified Mann-Kendall tests were employed to analyze the trends. The modified Mann-Kendall test was employed when lag-1 auto-correlation was present in the rainfall time series, thus taking care of presence of persistence in rainfall data series. Sen’s slope estimator was utilized to quantify the magnitude of rainfall trends. Results of trend test revealed that annual rainfall exhibited an increasing trend at three stations (Bayana, Baseri, and Karauli), with trend magnitudes ranging from 0.40 to 6.37 mm year^-1, whereas the other three stations did not show any discernible trends. Seasonally, significant increase in rainfall occurred at Bari, Bayana, Karauli, and Sapotra stations during the pre-monsoon season, and at Baseri and Bayana stations during monsoon season. No significant trends were observed in post-monsoon and winter seasons at any station. In case of monthly rainfall, a significant positive trend was detected at Baseri station in September, Bari station in March, Bayana and Karauli stations in January, and Sapotra station in January and April. This study emphasized on the use of variance-corrected Mann-Kendall test in order to take care for the presence of serial correlation in time series. The outcomes of the study could play a vital role in ensuring sustainable use and conservation of water resources under changing climate conditions.