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Lake Powell Lake Powell is a reservoir on the Colorado River, straddling the border between Utah and Arizona (most of it, along with Rainbow Bridge, is in Utah). It is a major vacation spot that around 2 million people visit every year. It is the second largest man-made reservoir by maximum water capacity in the United States behind Lake Mead, storing 24,322,000 acre feet (3.0001×1010 m3) of water when full.  Lake Powell was created by the flooding of Glen Canyon by the Glen Canyon Dam, which also led to the creation of Glen Canyon National Recreation Area, a popular summer destination. The reservoir is named for explorer John Wesley Powell, a one-armed American Civil War veteran who explored the river via three wooden boats in 1869. In 1972, Glen Canyon National Recreation Area was established. It is public land managed by the National Park Service, and available to the public for recreational purposes. Drought Upon completion of Glen Canyon Dam on September 13, 1963, the Colorado River began to back up, no longer being diverted through the tunnels. The newly flooded Glen Canyon formed Lake Powell. It took 11 years for the lake to fill to the 3,700 feet (1,100 m) level, on June 22, 1980. The lake level fluctuates considerably depending on the seasonal snow runoff from the Rocky Mountains.[4][5][6] The all-time highest water level was reached on July 14, 1983, during one of the heaviest Colorado River floods in recorded history, in part influenced by a strong El Niño event.  In what locals nickname the “bathtub ring” runs for most of Lake Powell’s 1,900-mile shoreline, which is half as long again as the US west coast. The ring of white calcium carbonate absorbed into the rock from the water contrasts sharply with the deep colors of the sandstone (clearly visible in the video). These days, it also provides a dramatically visible marker of the crisis facing the Colorado river after years of diminishing snowfalls on the Rockies. Today the bathtub ring towers 100ft or more above the boaters as what federal officials are describing as the worst drought in the Colorado Basin in a century diminishes a river that provides water to 40 million people in seven states. Lake Powell – a crucial cog in the machinery of water delivery – is at only 45% of capacity currently and is larger than Lake Mead in total water capacity. The current 15-year drought is the worst drought in the last 100 years and based on tree ring studies going back to 1075 the region is now in fourth-worst drought since 1075. The longest drought seen in the last millennia was 60 years. So the drought and weather cycles have a natural variability to them but recent data is leading to a conclusion that warmer temperatures fueled by climate change are having a heavier impact on the region. Impact of Global Climate Change The current number of Americans relying on water from the Colorado river is 40M and growing annually and more than 4.5M acres of farm land. But flows in recent decades have been lighter than would have been expected given annual rain and snowfall rates — and a new study has pinpointed rising temperatures as the likely culprit. The newest research from the Geophysical Research Letters by academics and federal scientists, focused on the upper stretches of the river. It attempted to parse out the different roles of temperature, precipitation and soil moisture on the variability of yearly water flows since reliable record-keeping began in 1906. Annual Colorado River flows have naturally swung up and down over time, but the natural trends have been bucked in recent years and decades. The data seen in the region currently is now consistent with more of the global observations in terms of warming, that it’s not just a fluctuation that’s within that historical back and forth but that the Oscillation is now breaking away from normal variability ranges seen historically. Rising global temperatures appear to have been playing a larger role in reducing the flows of water down the Colorado River since the late 1980s. As temperatures initially increase more snow actually falls in lieu of rain. These earlier temperature rises cause the snow packs to melt earlier. The combined effects of this actually lengthens the growing seasons of riverside vegetation, which allows it to suck up much more water than normal as it grows, along with more water loss to due evaporation. However, as temperatures continue to rise scientists predict we could then then see a shift away from more snow pack and into more rain fall which would then lessen the total volume of snow pack and reducing the water volumes of the snow pack that that melt slowly to fill up rivers. It is further predicted that rising temperature will cause storms to shift southward which exacerbate the diminishing snow pack even more. Excerpted from Wikipedia, the Guardian, Climate Central, and Kenyon.edu