Great Salt Lake Causeway

September 05, 2012


: Brent Watson
Summary Author: Brent Watson

The photo above shows the causeway that cuts across Great Salt Lake in Utah. The original transcontinental railroad was built to the north of the lake and completed in 1869. In 1904, the Southern Pacific Railroad created a shorter route directly across the lake called the Lucin Cutoff, reducing the distance of the railway by 42 mi (68 km). The original rail was built with a 12 mi (19 km) open trestle in the middle of the lake. This trestle allowed free flow of the brine from the north arm of the lake to the southern portion. However, by the 1950s the trestle became too expensive to maintain and was replaced with an earth-fill causeway. The causeway has impeded the free exchange of water from the north and south. Most of the inflow of water into the lake comes into the south arm. By 1988, the south arm of the lake was several feet higher than the north arm, and the salinity of the south arm had fallen significantly. A 100 ft (30 m) breach in the causeway installed in 1988 allowed the elevations and salinity to equalize to a certain extent. Further modifications to the breach along with lake level fluctuations have kept the salinity in the north arm at saturation levels (about 27 percent salt) while the south arm fluctuates between 5 and 15 percent.

The lower salinity of the south arm creates a different ecosystem than that of the north arm. The south arm is dominated by blue-green algae, which colors the water green. However, the higher salt content of the north arm allows the growth of the alga Dunaliella Salina which accounts for the distinctive wine red color. Photo taken on April 12, 2008.

Photo Details: Camera: NIKON D80; Focal Length: 50.0mm (35mm equivalent: 75mm); Aperture: f/7.1; Exposure Time: 0.0050 s (1/200); ISO equiv: 100; Software: Adobe Photoshop CS4 Windows.