Impacts of Precipitation Trends on Reservoirs and Rivers in Puerto Rico from 1990 to 2022

Monitoring hydrologic variables over rivers and reservoirs is crucial for gaining insight into, preparing for, and mitigating future extreme weather events. This study aims to determine whether rainfall activity has contributed to changes in the rivers and reservoirs of Puerto Rico. Data from 114 stations across 19 watersheds between 1990 and 2022 were used to evaluate historical precipitation, reservoir surface elevation, river discharge, and gauge height. The Mann-Kendall test was used to detect trends, Sen’s slope test was applied to assess their magnitude, and correlation was used to determine the relationship between hydrological variables. Trend results showed that precipitation has decreased on average over the past 30 years, while surface elevation in reservoirs has increased. A similar tendency was observed for discharge and stream gauges in rivers, where contradictory trends may be due to factors other than precipitation. Correlations reflected these observations, where precipitation had a weak relationship with surface elevation and a strong relationship with river variables, but not across a large number of stations. Factors such as inadequate maintenance or sediment accumulation may be more significant contributors to this trend.