According to a new study by the U.S. Geologic Survey, warmer springs over the past 30 years have cost the Rocky Mountains about 20 per cent of their snow cover, putting water supplies at risk, and increasing the dangers of both flooding and wildfires.
The annual runoff from the Rocky Mountain snowpack supplies between 60 and 80 per cent of the water that the residents of the western United States use every year, according to the USGS report. When this runoff starts, and how long it lasts, is very important for farmers who need the water to irrigate their crops and for hydroelectricity production. The timing is also a big concern for anyone who may be affected by flooding, wildfires and other disasters.
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If the spring melt starts early and is over quickly, the first problem this creates is a greater chance of flooding, especially in the lowlands along the rivers that funnel the water away from the mountains. Streams and rivers that were carved when the runoff happened over a much longer period of time just can't handle the increased flow, and anyone living along those waterways is in danger when the waters spill over their banks.
An added concern of all that snow melting is an increased risk of avalanche, as rapidly-melting snow further down the mountain can destabilize the snowpack higher up. Landslides can be more common as well, especially in areas where logging occurs or have been ravaged by wildfires, as the increased flow of water through the topsoil can produce a shifting mass of earth that quickly succumbs to gravity and destroys everything in its path.
On the economic side, earlier spring runoff forces municipalities to build larger reservoirs, as water that once flowed in at much slower rate suddenly becomes a deluge that can quickly overwhelm existing reservoirs. This can cost taxpayers millions, or billions, of dollars.
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Once this quick, early melt is over, a whole new set of issues emerge.
Water levels in both rivers and reservoirs drop, reducing the amount of electricity that can be generated at hydroelectric plants along the waterways, and putting water supplies for area residents at risk. Low water levels in rivers and streams also threaten wildlife populations, such as salmon, who depend on the water levels, not only to reach their spawning grounds, but also to reproduce when they get there. Wildfires are another major issue from all this, as forests become drier and more vulnerable, due to lower water levels later in the season. According to the National Interagency Fire Center, nine of the top ten largest wildfires in the United States happened in the last 10 years, and 2013 is projected to be bad as well.
According to the study, the reason for the decline isn't clear, though. There are natural temperature trends to consider, as well as the influences of large-scale weather patterns, such as El Niño-La Niña in the Pacific Ocean and the Arctic Oscillation in the North Atlantic, and also the effects of climate change. However, "disentangling" their influences, to tell how much each contributes, isn't easy to do in cases like these, even when looking at longer time periods.
A previous USGS study of the Rocky Mountain snowpack did reveal a trend that showed, up until the 1980s, a deeper snowpack in the southern and central Rockies was 'balanced' by a lesser snowpack in the northern Rockies, and a larger snowpack in the northern Rockies would mean a less snow in the central and southern Rockies. This new study builds upon that, and shows, even as this 'balanced' trend continues, there has been a general decline in snowpack depth across the entire mountain range over the past 30 years.
"Each year we looked at temperature and precipitation variations and the amount of water contained within the snowpack as of April," Greg Pederson, the scientist with the USGS who led the study, said in a statement. "Snow deficits were consistent throughout the Rockies due to the lack of precipitation during the cool seasons during the 1930s — coinciding with the Dust Bowl era. From 1980 on, warmer spring temperatures melted snowpack throughout the Rockies early, regardless of winter precipitation. The model in turn shows temperature as the major driving factor in snowpack declines over the past thirty years."
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Western Canada is also going to be affected by these same issues.
According to the B.C. government, unseasonably warm weather at the beginning of May this year caused a rapid melt of the snowcap, and flood watches were issued on May 12th and again on May 23rd. The situation was even worse in 2012, as a higher-than-normal snowpack for that year in the Fraser River basin raised concerns about flooding, and these were confirmed as hot, rainy weather in late April forced evacuations in the Okanagan-Similkameen region due to rising flood waters.
We've already seen alerts and evacuations due to wildfires in British Columbia and in Alberta this year, with Alberta going so far as to declare an early start to the season. Also, although the wildfire seasons in the past two years were fairly quiet, 2009 and 2010 were two of the busiest seasons in the past 10 years for both BC and Alberta.
Although figuring out the exact contribution of the various factors causing this is going to prove difficult, the natural temperature variations and shifts in El Niño have both been going on for a very long time. The newest influence being exerted on the whole system is human-enhanced climate change, which is the one influence we actually have the power to do something about. Faced with the prospect of losing our homes due to flood or fire, with dwindling water supplies for not only ourselves but the food we grow, and in reduced electricity production to keep our society running smoothly, this is an issue we should be addressing sooner rather than later.
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