Salt evaporation ponds, also known as salt pans or salt flats, are human-made or naturally occurring shallow ponds designed for the production of salt through the evaporation of seawater or brine. Salt ponds have been used by humans since ancient times, and flourish today for salt production. These ponds are commonly found in coastal areas that provide the water, and with warm and arid climates, which enable the evaporation.
The process of salt production in these ponds typically relies on natural evaporation (which can take up to years in some cases), leaving behind salt crystals that can be harvested. There are around 4-5 ounces of salt in a gallon of seawater, which is roughly 3% saline. The aim is to remove the water and thus increase the salinity. As this happens, and water becomes saltier, it also changes color, in quite beautiful ways that can be seen from aerial and even satellite observation.
Evaporation ponds are typically arranged in a series (often referred to generally as a saltern), with water being pumped progressively from one to the next as it becomes more saline. Evaporation slows down as the water becomes more saline, but eventually salt crystals accumulate in the final, harvesting pond. Once the final pond is completely evaporated, the dry salt is harvested using large raking equipment, and then rinsed and prepared for distribution.
Salt pond liners can be used in the initial ponds and even the harvesting pond, depending on liner material used. Many ponds are created simply on coastal soil that is relatively impermeable, but a geomembrane pond liner may be used where environmental concerns arise, to prevent leaching into the ground. Using a suitable synthetic liner can also result in a higher quality product.
Salt producers obviously prefer bodies of water with a higher salinity to begin with. Pond evaporation and salt harvesting tend to occur around super-salty bodies of water, as well as shallow coastlines with easy access to both land and seawater.
Notable areas in the USA where you can find salt ponds include San Francisco Bay, which has long had commercial salt production. The Salton Sea, also in California, is a very saline body of water and has also long been used for salt evaporation.
On the Texas coast, Galveston Bay contains naturally occurring salt ponds and marshes used for salt production. And Laguna Madre, a super-saline lagoon along the Texas coast, also hosts a number of salt ponds for commercial salt production.
The southern portion of Florida has salt evaporation ponds used for salt production, and its Atlantic coast is also prolific for this, particularly in the Everglades region. And in Utah, the Great Salt Lake, as the name suggests, is a highly saline lake, which can produce salt naturally in the shallower areas, as salt crystallizes during periods of low water levels. Salt from different regions and from around the world can vary considerably. Beyond the simple sodium chloride of basic table salt, sea salts and specialty salts may contain trace minerals, valued for their health aspects or for their distinct flavors and colors.
