Assessing the Impact of Drought in Guanacaste, Costa Rica and Evaluating Potential Contributions of ECOSTRESS Evapotranspiration Data to Improve Drought Estimation

Date of Award


Degree Type


Degree Name

Master of Science in Geography



First Advisor

Christopher A. Williams

Second Advisor

Christine M. Lee

Third Advisor

Ron J. Eastman


First, this study quantifies the annual change in precipitation and analyzes historical rainfall patterns using the Standard Precipitation Index (SPI) with combined precipitation datasets from the Global Precipitation Climatology Centre and the Costa Rica Instituto Meteorologico Nacional. The research then assesses plant stress at a regional scale by examining annual and seasonal anomalies from 2000-2015 in normalized difference vegetation index (NDVI) data at 30m spatial resolution and comparing these results to the coarser 1km ET, potential evapotranspiration (PET) and evaporative stress index (ESI) anomalies in Guanacaste at 1km spatial resolution from PT-JPL. The third phase of analysis investigates the differences in plant stress and drought resilience observed across different categories of landscapes in Guanacaste, including forest, grassland and agriculture. Results from the SPI analysis suggest that Guanacaste experienced a long term negative trend in precipitation over the past 15 years relative to the historical rainfall data, with 2015 having the most severe drought conditions (annual SPI = -4.07). The NDVI, ET, PET and ESI analyses reveal that the greatest amount of plant stress experienced in the region during the drought occurred in 2014, particularly during the wet season. Furthermore, differences in drought response across land use categories varied significantly (p<0.001). The findings of this research illustrate how ECOSTRESS ET information can help improve drought estimation through complementing the current suite of precipitation-based drought indicators.