Beyond the Great Lakes that surround my native Michigan, the next largest lake in the United States is the Great Salt Lake in northern Utah. Although the lakes of both states share similarly impressive surface areas they are incredibly different in their geologic processes and resulting ecosystems and economic impacts.
The Great Lakes are the continent’s largest bodies of fresh water and teem with a massive array of fish and other interrelated organisms. This region receives a generous amount of annual rainfall, and all that water makes its way through streams and rivers across a vast watershed and eventually reaches the Great Lakes. There it collects and waits before it finally makes its way out to the Atlantic Ocean via the Saint Lawrence Seaway between the US and Canada. The constant flow of water ensures that salts and other minerals are continuously flushed out to sea and the system as a whole remains fresh. The abundance of fresh water lakes, rivers, and estuaries provide countless homes for a staggering array of invertebrates, fish, amphibians, reptiles, birds and mammals. Tourism and sport fishing are multi-billion-dollar industries, and the open channels to the sea provide billions of dollars in economic transportation benefits.
The Great Salt Lake, in contrast, harbors an entirely different yet equally fascinating environment borne of its unique geography. Located in the Great Basin of the intermountain west, this area is defined by its watersheds having no connection to the ocean. Runoff from relatively dry mountains and valleys collects in streams and rivers and makes its way to lakes, but from there the water has no outlet. Instead of flowing out to the sea it just sits and evaporates in the hot desert sun. Since salts and other minerals are not flushed out to the ocean they instead collect in these basins. They accumulate over time, increase the salinity of the lakes, and amass substantial mineral deposits. While the average salinity of the world’s oceans is around 3.5%, the salinity of the Great Salt Lake can fluctuate between 5% and 27% depending on location and environmental factors.
The unique hydrologic cycle of the Great Basin gives the lakes within its borders some novel characteristics. The most common life forms within the water tend to be brine shrimp, brine flies, and salt-loving or salt-tolerant species of algae and bacteria. These novel yet abundant organisms provide a vast food source for a wide variety of migrating birds. Although the Great Salt Lake appears inhospitable to life, it actually hosts a complex web of organism interactions.
The abundant salt and other mineral accumulations within the Great Salt Lake have also offered opportunities for industry. Deposits of sodium chloride, magnesium chloride, potassium sulfate, and other minerals have been significant for such uses as water-softening, ice melt, salt lick blocks for livestock, dust suppressants, fertilizers, magnesium metal, and chlorine gas. The Great Salt Lake and other lakes of the Great Basin have proved not only invaluable to unique organisms, but to unique human needs as well.