As the new home of TexPIRG’s environmental work, Environment Texas can be contacted with any questions regarding this report.
In the American West, no other effect of climate disruption is as significant as how it endangers the region’s already scarce snowpacks and water supply. With the inherent vulnerability of the dry West to even small changes in the snow-water cycle, these risks alone present ample reason for Westerners to take action to protect this special region.
The Likely Effects of Climate Disruption on the West’s Water
Scientists believe that climate disruption in the West likely will result in more heat, less snowpack, and earlier snowmelt and runoff. This may be accompanied by other adverse effects, including increased intensity, frequency, and duration of drought.
• More heat. Temperature increases in the West are likely to be even greater than the projected 3° to 10°F worldwide increase by the end of the 21st Century, compared to 1990. The heating is likely to be greater in the winter than in the summer and at higher elevations than in lowlands, with significant implications for snowpacks and water availability.
• Smaller snowpacks. It is very likely that more winter precipitation will fall as rain instead of snow, periods of snowpack accumulation will be shorter, and snowpacks will be smaller.
• Earlier snowmelt. Warming earlier in the year very likely will melt snowpacks sooner. Peak water flows would occur that much sooner than the summertime peak water needs of cities, farmers and ranchers, and others.
• More evaporation and dryness. Higher temperatures would increase evaporation from streams and reservoirs, soil dryness, and the needs of crops and other plants for supplemental water.
• More flood-control releases. Warming in the mountains in late winter and early spring very likely will increase snowmelt and river flows then, and reduce them later in the year. The risk of flooding likely will increase, and water managers may be forced to make flood-control releases more often from reservoirs, leaving less water to be stored for summertime needs.
• Less groundwater. Snowpacks also are essential contributors to the West’s groundwater, so reduced snowpacks could reduce groundwater supplies, too.
• More legal restrictions. Environmental constraints, which sometimes now limit the water available for consumptive use in the West, may be triggered more often as a result of climate disruption. Changes in water supplies also may trigger water-use restrictions under interstate compacts.
• More droughts. Climate disruption could lead to more intense, frequent, and longer-lasting droughts in the interior West.
More heat, less snowpack, less available water, and possibly more droughts are likely to lead to other changes across the West. Most significantly, wildfires are likely to increase in number and severity.
Climate Disruption Is Under Way In the West
It is now accepted by the scientific community that, worldwide, the climate is changing as a result of human activities. In the American West, too, climate disruption is under way.
• More heat. The United States, along with the rest of the world, has warmed, with temperature increases in the West greater than in other regions of the contiguous states.
• Less snowfall. As the West has warmed, less winter precipitation now is falling as snow and more as rain.
• Smaller snowpacks. At most snowpack-measurement sites across the West, snowpack levels have declined over the period 1950 to 2000.
• Earlier snowmelt. Across the West, springtime peak streamflows are earlier than 50 years ago. In many cases, the peak snowmelt advanced by 10 to 30 days.
• More wildfires. Wildfire in the West has increased, particularly in the last two decades. Researchers have identified climate factors as being a significant contribution to this trend.
For this report, the Rocky Mountain Climate Organization (RMCO) conducted a new analysis of government temperature and snowpack records for the upper basins of the Columbia River, Missouri River, Colorado River, and Rio Grande for evidence of human-caused climate change.
• Increased temperatures. In each river basin, the most recent five-year period was the hottest in the past 110 years. In the upper Columbia River basin, 2000-2004 was 1.5°F hotter than the historic average; in the upper Missouri basin, 1.5°F hotter; in the upper Colorado basin, 2.1°F hotter; and in the upper Rio Grande, 2.5°F hotter. These temperature increases coincided with and worsened the effects of the recent West-wide drought, by increasing evaporation rates from streams and reservoirs, soil dryness, and the water needs of crops and other plants.
• Greatest warming in winter and spring. In all four basins, the monthly pattern of the warming that occurred in 1995 through 2004 reveals what could be regarded as a signature of climate disruption: The warming has been greatest in January, February, and March. This timing is consistent with predictions that warming resulting from climate disruption will be greatest in winter and spring. Also, this is when warming has the greatest effects on the size of snowpacks and the timing of snowmelt.
• Reduced snowpacks. At government snowpack-measurement sites with records going back to 1961, from 1990 on snowpack levels have been below average for 13 of the last 16 years in the Columbia River basin, 11 of 16 years in the Colorado River basin, 14 of 16 years in the Missouri River basin, and 10 of 16 years in the Rio Grande basin.
In sum, the RMCO analysis offers further evidence that climate disruption is already under way in the West in ways that jeopardize the region’s snow and water resources.
Projections of Future Changes
Scientists believe that the changes in climate observed so far are just a mild foretaste of what is likely to come if global-warming emissions continue to increase. A few illustrative examples of climate projections for the West from recent scientific studies include:
• For the Colorado River basin, losses of 24% of the basin’s snowpack are predicted by 2010-2039 and 30% by 2040-2069.
• For the Columbia River basin, losses of 35% of the basin’s snowpack are predicted by 2050 and 47% by 2090. For the milderwinter Cascade Mountains, the predicted losses are nearly 60% by 2050 and 72% by 2090.
• For California, losses of 29 to 89% of the state’s snowpack are predicted by 2070-2099.
Changing the Odds
With all that the West has at risk, the region has good reason not only to do its share to deal with climate disruption, but also to be a leader in showing the rest of the nation and world what can be done. Encouragingly, there are growing signs of new western leadership and action in addressing climate disruption. Much more needs to be done, but these first steps suggest that Westerners are beginning to choose a new path to keep the region such a special place.