Spatio-Temporal Variability Assessment and Frequency Analysis of Precipitation over Northern Regions of Pakistan

Abstract

The hydro-meteorological factors of excessive rainfall are difficult to explain because of unexpected changes in climate and varying water demand as the population grows. The study aims to improve comprehension of the frequency and magnitude of total precipitation with the help of recent techniques and providing practical knowledge in making development strategies for water resource management in one of Pakistan's most significant climatic regions. For that purpose, spatio-temporal rainfall variability, trends analysis, and regional rainfall frequency analysis for multiple meteorological stations in Gilgit Baltistan are performed. The data of precipitation is acquired from Pakistan Meteorological Department spanning 1990 to 2020. Temporal and spatial trend analysis are performed using Man Kendall test and Sen’s Slope technique and linear moments technique are utilized to calculate regional frequency analysis. For regional frequency analysis data series are random, independent and identical distributed, and no site is discordant in the region. The selection of distribution is done by methods of L-moments ratio diagram and Z-statistics. Generalized Pareto Distribution (GPA) is appeared to be the most suitable distribution to represent the statistical properties of precipitation data. The results show that the station of Astore, Hushey and Khunjerab have observed annual trends. Astore has experienced a decreasing trend of 186 mm of rainfall whereas Khunjerab and Hushey have experienced an increasing trend of 230 mm and 252 mm over last three decades. Some of the stations have also experienced seasonal trends. Moreover, most of the stations have not observed any significant trends in rainfall. The results of regional frequency analysis have shown that the stations of Astore, Naltar, Rattu, Rama, Khunjerab and Hushey are at higher risk of observing extreme rainfall events 100 years return period event in any of coming year. The study could help in hydrological planning and irrigation water resources management, and in policy making in disaster prevention and mitigation.