Concurrent increases in wet and dry extremes projected in Texas and combined effects on groundwater

Abstract

The US state of Texas has experienced consecutive flooding events since spring 2015 with devastating consequences, yet these happened only a few years after the record drought of 2011. Identifying the effect of climate variability on regional water cycle extremes, such as the predicted occurrence of La Nina in winter 2017-2018 and its association with drought in Texas, remains a challenge. The present analyses use large-ensemble simulations to project the future of water cycle extremes in Texas and assess their connection with the changing El Nino-Southern Oscillation (ENSO) teleconnection under global warming. Large-ensemble simulations indicate that both intense drought and excessive precipitation are projected to increase towards the middle of the 21st century, associated with a strengthened effect from ENSO. Despite the precipitation increase projected for the southern Great Plains, groundwater storage is likely to decrease in the long run with diminishing groundwater recharge; this is due to the concurrent increases and strengthening in drought offsetting the effect of added rains. This projection provides implications to short-term climate anomaly in the face of the La Nina and to long-term water resources planning.