Future Changes in Simulated Streamflow in Costa Rica from CMIP6 climate models

Abstract

Statistically downscaled daily data from an ensemble of five General Circulation Models (GCMs) from the Climate Model Intercomparison Program 6 (CMIP6) will be used to determine changes (with respect to a baseline historical scenario) in the magnitude of the 20-year return period streamflow for 34 basins covering Costa Rica at horizons corresponding to mid-century and end-of-century. The climate models used were selected according to Almazroui et al. (2021), which proved to have the lower biases in reproducing the region’s climate. The chosen downscaling method corresponds to a delta approach described in Navarro-Racines et al. (2020). The hydrological simulations were computed using the HBV model. The concentration scenario selected for this study is SSP5-8.5, considered a pessimistic scenario. Preliminary results show precipitation increases in the Pacific Slope, however, the increases in actual evapotranspiration due to warming over exceeds the precipitation effects, causing a future reduction in streamflow in basins in the Pacific Slope and reductions in the Northern Caribbean region of Costa Rica. This is important as it suggests that the North Pacific, a climatologically drier region, will experience significant increases in aridity. This region is known to present social and economic vulnerabilities, as it is part of the Central American Dry Corridor.