International Journal of Scientific Research and Engineering Development

Water resources, agriculture, flood risk and climate adaptation are the sectors and issues greatly impacted by rainfall variability and extreme rainfall events, especially in low lying coastal areas. The current study investigates the variability and extremes of rainfall over coastal Guyana for the period 1981 to 2025. Rainfall characteristics, long-term trend, structural breaks, and extreme rainfall behaviour were assessed using descriptive statistics, rainfall anomaly analysis, Mann–Kendall trend test, Sen's slope estimator, Bai–Perron structural break analysis and the Generalized Extreme Value (GEV) model. The results revealed that there is a significant variation in time, mean annual rainfall of 2278.91 mm and coefficient of variation of 21.79%. The rainfall showed a distinct bimodal seasonal distribution with main wet season between May and July and secondary wet season between November and December. Trend analysis showed a weak positive trend (Sen's slope = 4.03 mm year−1) but not significant at the Mann– Kendall p level (> 0.286), indicating that the longitudinal variability is the prevailing feature of the behaviour of rainfall. The results of the structural break analysis showed that the year 2003 was the year of a major shift in rainfall pattern. There were further changes in 1985 and 1987 as detected by the PELT change-point detection, which reveals episodic changes in rainfall pattern. The GEV analysis revealed that high magnitude rainfall events are possible and that estimated return periods of 2,958.66 mm, 3,390.99 mm and 3,731.46 mm for 10 year, 25 year and 50 year rainfall return periods respectively. The results of this study provide a detailed understanding of the rainfall characteristics over coastal Guyana and are of great value for monitoring climate conditions, flood risk management, water resources planning, and climate adaptation.

Bibi Sherriza Ali, Jason Phillips, Shemuel Carmichael, "Rainfall Variability and Extreme Rainfall Events in Coastal Guyana (1981–2025)" International Journal of Scientific Research and Engineering Development, V9(4): Page(250-258) May-June 2026. ISSN: 2581-7175. www.ijsred.com. Published by Scientific and Academic Research Publishing.