Concurrent Changes in Extreme Hydroclimate Events in the Colorado River Basin

Abstract

Extreme events resulting in catastrophic damage have more than doubled in the last five years, costing hundreds of lives and thousands of homes, and heavily undermining regional economic stability. At present, most of these hydroclimatic extreme events are documented by the media as individual events; however, in scientific terms, many are better understood as concurrent events—concurrent extremes of both temperature and precipitation (e.g., drought, floods). This paper considers concurrent changes in hydroclimate extremes, including heatwaves, drought, flooding, and low flows, in six historical-to-future (1970–1999, 2070–2099) Earth System Model (ESM) climate scenarios for the Colorado River basin. Results indicate that temperature-driven Impacts (heatwaves, drought) have the strongest responses while precipitation-drive Impacts have weaker responses. All Impacts exhibit an increase in magnitude from synoptic to annual time scales, with heatwaves increasing in strength about three times at the annual time scale versus the synoptic, while low flows only increase slightly. Critical watersheds in the Colorado were identified, highlighting the Blue River basin, Uncompadre, East Taylor, Salt/Verde watersheds, locations of important water infrastructures, water resources, and hydrological research. Our results indicate that concurrent extreme hydroclimate events are projected to increase in the future and intensify within critical regions of the Colorado River basin. Considering extreme hydroclimate events concurrently is an important step towards linking economic and social effects of these events and their associated instabilities on a regional scale.

Three-decade assessment of dry and wet spells change across Iran, a fingerprint of climate change

“…Moreover, a growing body of evidence confirms that global warming can create or intensify compound climate extreme events, leading to more significant impacts on hydro-ecological systems than individual extremes alone 32 . Despite a wide range of extreme compound events, drought, coupled with heat waves, is a typical example of compounding extremes in arid and semi-arid regions 33 , 34 . Confirming the importance of assessing such hydro-climate extremes for decision making, precipitation and temperature trends have been studied simultaneously by recent literature 35 – 40 .…”

Expectations of Future Natural Hazards in Human Adaptation to Concurrent Extreme Events in the Colorado River Basin

“…For this work, we used synoptic time scale (maximum daily values extracted for 5 days periods, with 73 5-day intervals in each year) data for each of three extreme flooding indicators following the work described in Bennett et al [29]: maximum soil moisture in the entire soil column, maximum precipitation, and maximum runoff. We consider a historical period S1).…”

“…In the Southwest climate region (Arizona, New Mexico, Colorado, and Utah), flooding, drought, freezing events, severe storms, and winter storms events cost approximately 36 billion dollars and resulted in 770 deaths between 1980 and 2020 ( [28]). The importance of the Colorado and the potential impact of changing extremes on the economy of the basin highlights the need for closer examination of changing concurrent extreme events ( [29][30][31]).…”

Limits of thermal and hydrological tolerance in a foundation tree species (Populus fremontii) in the desert southwestern United States

“…The lower Colorado River corridor that extends from Lake Mead near Boulder City, Nevada, to the river's terminus at the Sea of Cortez in northwestern, Mexico, is among the warmest regions in North America, experiencing temperatures that approach, or even exceed 50°C in midsummer, with more frequent and intense heat waves predicted (Tillman et al ., 2020; Bennett et al ., 2021). As a consequence of these novel climate conditions, the highly heat adapted riparian flora that persist along the lower Colorado River corridor are at risk of rapidly becoming maladapted to their local environment.…”