Every year, streams and rivers are fed in the spring by fresh cold water given off by the melting snowpack. Since the 1950s, snowpack for spring snow melt in the mountains of the U.S. Northwest is declining, and this trend is projected to continue as the climate warms further this century. While precipitation has increased throughout the 1900s-2000s, temperature increases have had the overpowering affect on the snowpack (Hamelt 4559). Reduced snowpack and early snow melts in areas such as the Rockies, Sierras, and Cascades is likely to hurt hydropower during parts of the year, and to place other stresses on the region's water supply (Serreze 35). Rivers that rely on the snowpack melt later in the spring such as the Columbia River or the Colorado River are losing large portions of their usual spring snow melt (Stewart 1). Growing demand and decreasing supply has the Colorado River running dry before the flow makes it to supply the water deprived areas of Mexico. Runoff from winter snowpack accounts for about 70 percent of the annual water supply for more than 30 million people living in the western United States, nearly 10% of the U.S.’s population (doi.usgs). This rapid change in the snowpack decreasing yields and melting earlier in the season has a domino effect on all aspects of the region. Agriculture, fresh water supply, wildlife, landscape and hydropower are all seeing direct results from the warmer winter months changing western North America’s snowpack.
The snowpack is a necessary piece of nature. The yearly recurrence of winter mountain snowfall is a critical backbone for water resources in western North America. The mountain snowpack provides natural storage of fresh water from the cold season until it gradually melts during the spring, replenishing rivers and aqueducts. Western North America relies heavily upon this fresh water source. A huge amount (sometimes more than 70%) of stream flow in the western United States begins as melting mountaintop snowpack. The climate of western United States receives more precipitation in the winter. Although this water is stored directly in groundwater and soil, snow accumulation is the leading method by which winter precipitation is held for the dry summer months (Mote 30). When these areas experience milder temperatures in the winter, this stored resource is released to early for its use during the summer months. The already low flows of late summer are projected to decrease further due to both earlier snowmelt and increased evaporation and water loss from vegetation.
Image 1. Columbia River in the state of Washington.
Agriculture is a very important sector in economies across western North America. California is one of our nation’s leading producers in fruits and commodities such as wine. States such as Colorado still have agriculture but run most of their revenue through livestock, which still remains water demanding. However, these cannot be properly run without the help of irrigation. The region does not receive enough consistent precipitation nor does it have great natural sources of freshwater for agriculture. Large fresh water sources such as the Colorado River lose one third of their flow to agriculture in the region. Arizona has 25 percent of its water provided by the Colorado River. Of this water, 80 percent of it is used for agriculture. The river is responsible for providing 15 percent of U.S. crops and about 13 percent of their livestock (CRWUA). Some areas of California could only have access to 30 percent of the water ordered for farming this year as stated in April 2012 by the Business Journal. Therefore, this water is taken along great distances from rivers supplied by the spring melt of the snowpack. As far as a fresh water supply, the northwestern area of North America is not in as much trouble as the southwest. The southwest relies heavily on lakes, streams, and rivers that are refilled every spring by the...
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