The Great Salt Lake in Utah Is Divided Into a Blue and a Red Body of Water – Here’s Why

The Great Salt Lake, a shimmering expanse in Utah, has a surprising feature. A giant railroad causeway slices through its center, creating two distinct bodies of water with vastly different characteristics. On one side, a vibrant blue beckons, while the other boasts a mysterious red hue.

The culprit behind this aquatic split is the Lucin Cutoff, a 102-mile railroad shortcut built in the early 1900s. Prior to the causeway, trains navigated the Promontory Mountains, adding significant distance and time to the journey. The shortcut, however, came at a cost.

Originally a wooden trestle bridge, the causeway hindered the natural water flow within the lake. In the 1950s, it was replaced with a solid rock-fill causeway, further restricting water exchange and leading to the formation of two distinct arms – north and south.

The south arm, bathed in a brilliant blue, receives a constant freshwater infusion from three major rivers: the Bear, Weber, and Jordan. This dilutes the salt content, making it much less concentrated than ocean water.

The north arm, on the other hand, tells a different story. Cut off from the freshwater influx, it has become a hypersaline haven – almost ten times saltier than the ocean!  This extreme environment thrives with unique, salt-loving organisms like brine shrimp, brine flies, nematodes, and several forms of algae. These tiny creatures are responsible for the north arm’s striking red color, a breathtaking contrast to its southern counterpart.

The wetlands along the eastern and northern edges of the Great Salt Lake, on the other hand, provide crucial habitats for millions of migratory shorebirds and waterfowl in western North America. These areas account for approximately 75% of Utah’s wetlands.

The Lucin Cutoff undeniably revolutionized railway transport, but its impact on the Great Salt Lake ecosystem cannot be ignored. Efforts are underway to mitigate the causeway’s effects. In 2016, a breach was created beneath a newly constructed bridge, allowing for some water exchange and hopefully restoring a more natural balance to this fascinating, divided lake.

That’s all the more important as the Great Salt Lake has shrunk dramatically since 1987 due to drought, climate change, and overuse of snowmelt, with its area decreasing from about 3,300 square miles to just 950 square miles as of July 2022. The lake’s surface elevation has also fluctuated significantly, reaching its lowest recorded level in December 2022. Without policy changes, scientists estimate the lake could dry up by 2028, threatening local ecosystems.

Sources: 1, 2, 3, 4