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The Likely Effects of Climate Disruption on the West's Water

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  • mtneuman@juno.com
    Sept. 2005 Executive Summary In This Chapter: Introduction The Likely Effects of Climate Disruption on the West s Water Climate Disruption Is Under Way In the
    Message 1 of 1 , Dec 6, 2005
      Sept. 2005
      Executive Summary
      In This Chapter:

      Introduction
      The Likely Effects of Climate Disruption on the West's Water
      Climate Disruption Is Under Way In the West
      New Findings
      Projections of Future Changes
      Changing the Odds

      Introduction
      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. 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
      "Today, in some areas of the West, existing water supplies are, or will
      be, inadequate to meet the water demands of people, cities, farms, and
      the environment even under normal water supply conditions." - U.S.
      Department of the Interior, "Water 2025: Preventing Crisis and Conflict
      in the West" (2003) 1
      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
      "What this work shows is that, even with a conservative climate model,
      current demands on water resources in many parts of the West will not be
      met under plausible future climate conditions - much less the demands of
      a larger population and a larger economy." - Dr. Tim P. Barnett and
      others, "The Effects of Climate Change on Water Resources in the West:
      Introduction and Overview" (2004)56
      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.

      New Findings
      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 milder-winter 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.

      http://www.cleartheair.org/waterinthewest/pdfs/waterinthewest.pdf
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