The role of physical geography on Puerto Rico’s water budget

Abstract

Study region: Puerto Rico, a tropical island in the Caribbean Sea. Study focus: This study examines how water stress in Puerto Rico is influenced by its physical geography using a new USGS Soil-Water-Balance Model (Version 2.0) applied to three periods: a baseline climatology (1981–2010), a recent decade (2010–2019), and multiple drought years (1991, 1994, 1997, 2015). New hydrological insights for the region: Oceanic islands often experience chronic water stress due to their size, population, land use, and geomorphology. Yet more severe, acute stress arises due to atmospheric forcing droughts, in which decreased precipitation is accompanied by increased temperatures, evapotranspiration, and water withdrawals. Based on our analysis of the physical geography of Puerto Rico, we find that water stress is more likely in southern Puerto Rico during both baseline and recent decade conditions due to reduced net infiltration within the rain shadow of the Cordillera Central. On the contrary, chronic stress is lower in mountainous and vegetated areas on the remainder of the island, as well as where coastal aquifers are available for augmenting surface water. During drought events, water stress is more common in central and eastern Puerto Rico mainly due to reductions in precipitation and net infiltration, increased evapotranspiration, and limited groundwater availability. Drought imposes additional chronic stresses by reducing recharge to coastal aquifers. These coastal aquifers are recharged by direct rainfall and streamflow from central Puerto Rico; the decreased precipitation and net infiltration in those areas constrain water availability during drought.

Keywords

• Drought
• Water stress
• Tropical climate
• Puerto rico
• Caribbean islands