Climate change and water resources in a tropical island system: propagation of uncertainty from statistically downscaled climate models to hydrologic models

Abstract

Many tropical islands have limited water resources with historically increasing demand, all potentially affected by a changing climate. The effects of climate change on island hydrology are difficult to model due to steep local precipitation gradients and sparse data. This work uses 10 statistically downscaled general circulation models (GCMs) under two greenhouse gas emission scenarios to evaluate the uncertainty propagated from GCMs in projecting the effects of climate change on water resources in a tropical island system. The assessment is conducted using a previously configured hydrologic model, the Precipitation Runoff Modelling System (PRMS) for Puerto Rico. Projected climate data and their modelled hydrologic variables versus historical measurements and their modelled hydrologic variables are found to have empirical distribution functions that are statistically different with less than 1 year of daily data aggregation. Thus, only annual averages of the projected hydrologic variables are employed as completely bias-corrected model outputs. The magnitude of the projected total flow decreases in the four regions covering Puerto Rico, but with a large range of uncertainty depending on the makeup of the GCM ensemble. The multi-model mean projected total flow decreases by 49-88% of historical amounts from the 1960s to the 2090s for the high emissions scenarios and by 39-79% for the low emissions scenarios. Subsurface flow contributions decreased the least and groundwater flow contributions decreased the most across the island. At locations critical to water supply for human use, projected streamflow is shown to decrease substantially below projected withdrawals by 2099.

Ecology and conservation of the American eel in the Caribbean region

“…Climate change has an overarching influence on Caribbean water resources and is an important driver to be considered in conservation planning and policy. In Puerto Rico, precipitation and river flow are projected to decrease in all regions of the island, exacerbating the current water management of this limited resource (Henareh Khalyani et al, 2016;Van Beusekom, Gould, Terando & Collazo, 2016). By contrast, the number and intensity of tropical cyclones has increased with warming sea surface temperature, leading to extreme flooding events (Webster, Holland, Curry & Chang, 2005).…”

Drought Facilitates Species Invasions in an Urban Stream: Results From a Long-Term Study of Tropical Island Fish Assemblage Structure

“…Caribbean islands are vulnerable to climate change and extreme climatic events (Nurse et al, 2014;Khalyani et al, 2016). Future rainfall projections include changes in monthly, seasonal, and annual rainfall by the end of the century under global climate change scenarios (Van Beusekom et al, 2016). Projections show that by 2071-2100, mean annual rainfall will decrease from 25 to 50%, primarily because precipitation is expected to decrease by nearly 35% from August to October (Campbell et al, 2011).…”

“…This decrease in precipitation will result in severe reductions of annual stream flow. For example, hydrologic models project total flow reductions of 49-88% under high greenhouse gas emission scenarios and 39-79% under low emission scenarios (Van Beusekom et al, 2016). The Greater Antilles have already begun to experience major reductions in precipitation during recent years (Comarazamy and González, 2011;Stephenson et al, 2014), with 2015 categorized the year with the strongest drought in the last 50 years (Herrera and Ault, 2017).…”

Multi-model Hydroclimate Projections for the Alabama-Coosa-Tallapoosa River Basin in the Southeastern United States

“…An ideal but non-pragmatic way to characterize these uncertainties would encompass producing ensemble hydroclimate projections using a complete sample of uncertainty sources. However, given the limited resources, most impact assessment studies can focus only on a subset of these choices, thereby resulting in underestimation of the uncertainties in hydroclimate projections 7,13 .Given the plethora of choices in the above-mentioned modeling framework and their significance in hydroclimatic projections, many studies have investigated the effects of individual sources of uncertainties [14][15][16] , as well as combined uncertainties due to different methodological choices within the modeling framework 7,8,[17][18][19][20][21][22][23] . Several studies at global and regional scales indicate that the uncertainties from climate models are a more important source of uncertainty than other factors such as greenhouse gas emission scenarios and hydrologic model structures 8,12,19,24 .…”

“…Similarly, Chegwidden et al (2019) demonstrated that choices of GCM and greenhouse emission pathways are the dominant contributors to annual streamflow volume, and the choices of hydrologic model and parameters are prominent in capturing low-flow uncertainties over the US Pacific Northwest 23 . While multiple climate models and greenhouse gas emission scenarios have been used to capture the ensemble of climate scenarios in the past two decades, such studies are often limited to the choice of a single hydrologic model 17,20,22,[25][26][27] . Despite studies indicating that choice of hydrologic model can produce substantial differences in hydrologic projections, at times exceeding the mean signal from climate scenarios 11 , the use of multiple hydrological models has only begun to gain traction 21,28,29 .The selection of appropriate hydrologic model(s) in the modeling framework remains a challenge, as decisions so subjective in nature require careful consideration of several factors, including model applicability, suitable spatiotemporal scale of implementation, availability of computational resources, quality of meteorological forcings and land surface parameters, and the overall technical feasibility 30 .…”