Historic and Future Droughts in the Big Bend Region of the Chihuahuan Desert

Abstract

The future of ecosystems in the Big Bend region of the Chihuahuan Desert largely depends on the response to future droughts. Most of the precipitation in the region falls in the 6-month period from May to October due in large part to the Southwestern United States monsoon. There is considerably less interannual variability in precipitation during these 6 months than in the rest of the year. The interannual variations tend to occur simultaneously throughout the region, indicating that drought is a regional-scale rather than a local-scale phenomenon despite the hit-or-miss nature of summertime convection. There is uncertainty in the future of precipitation in the region, but the interannual variability of precipitation is expected to far outweigh any change in the long-term trend. However, future temperatures are expected to significantly increase, so past precipitation and temperature records were examined to determine periods that would serve as analogs for drought in a warmer overall environment. The identification of analogs relies in part on a detailed assessment of station metadata to assess the quality of their precipitation and temperature records. There is a greater availability of quality precipitation records in the region than temperature records, which are more influenced by changes in the land surrounding an observation site. Several future drought analogs were identified for the region. Most of the analogs occurred in the late 1990s or early 2000s. It is likely that some future droughts will occur with temperatures well beyond what has previously been observed in the area.