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Salt evaporation pond facts for kids

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Salt evaporation pond in Manaure
Salt evaporation pond in Manaure, La Guajira, Colombia

A salt evaporation pond is a special shallow area built to get salt from sea water or other salty water. These ponds are wide and not very deep. This allows the sun to warm the water and make it evaporate. When the water disappears, the salt is left behind.

What Are Salt Evaporation Ponds?

These ponds are sometimes called salterns or salt works. They are like big, flat pools where salty water sits under the sun. People fill these ponds with seawater or very salty water. As the sun shines, the water slowly turns into vapor and goes into the air. What remains is the salt, which can then be collected.

Salt ponds are also important places for many waterbirds. They offer a safe spot for birds to rest and find food. Some of these birds might even be rare or endangered. However, building these ponds can sometimes harm natural areas like mangrove forests and mudflats. This can change the environment and make it harder for other plants or fish to grow.

The Colors of Salt Ponds

Have you ever seen a salt pond that looks green, orange, or even bright red? The amazing colors in these ponds come from tiny living things called microorganisms. The color tells us how salty the water is.

In ponds that are not too salty, you might see green algae like Dunaliella salina. These can sometimes look orange too. As the water gets saltier, different types of tiny organisms called Halobacteria take over. These make the ponds turn pink, red, and orange. Other tiny bacteria also add to these beautiful colors.

Where Can We Find Salt Ponds?

Salt evaporation ponds are found all over the world. Here are some famous examples:

  • The Salterns of Guérande in France, known for their special salt.
  • The Cáhuil salt ponds in Chile.
  • The Manaure salt ponds in Colombia.
  • The Salineras de Maras, Peru in Peru, high in the mountains.
  • The saltworks of Alcácer do Sal, Comporta, and Castro Marim in Portugal.
  • The El Caracol solar evaporator in Mexico.
  • The Sečovlje and Strunjan salt ponds in Slovenia, by the Adriatic Sea.
  • The San Francisco Bay salt ponds in the United States. Many of these are now being returned to their natural state.
  • South Bay Salt Works in San Diego, California.
  • The Dead Sea salt ponds in the Middle East.
  • The salt ponds in Salina, Malta, which is named after salt pans.
  • Many large salt ponds in Western Australia, like Port Hedland, Dampier, Lake McLeod, Useless Loop, and Onslow.
  • Yellow Walls, Malahide, Ireland; active from 1770 to 1837.
  • Lake Grassmere in New Zealand.
  • The ancient salt pans in Marsala and Trapani, Sicily. Salt has been farmed here since the Phoenician period.
  • The Nature reserve of Margherita di Savoia in Italy, one of Europe's largest. Flamingos often visit here.
  • The salt works on the island of Great Inagua, owned by Morton Salt.
  • The salt harvesting by the Tsonga women of Baleni in South Africa.

Before World War II, people in Egypt near Alexandria had a unique way to get salt. They put posts in shallow seawater. The water evaporated, leaving salt on the posts, which made it easier to collect.

How Is Salt Made in These Ponds?

Salt pans are usually shallow and open to the sky. Sometimes, metal pans are used to help the water evaporate faster. These salt-making areas are often built close to where the salty water comes from. For example, ponds that use seawater are usually right on the coast. If the salt comes from underground brine (very salty water), the ponds will be near the wells that bring the brine up. Sometimes, extra heat from fires is used to speed up the evaporation.

A Look Back: The History of Salt Making

Learning about ancient salt making can be tricky. Sea levels have changed, and old salt-making sites were often destroyed or changed over time.

Early Salt Making

People in Europe started making salt very early, from the Neolithic period (New Stone Age) through the Iron Age. They mostly used salty water from inland sources and heated it to make the water evaporate. Large coastal solar ponds were best for warmer, dry places.

Evidence shows that people in Western Europe were making salt from the sea as far back as 5,000 BCE. They likely used natural coastal lagoons to make the seawater saltier before heating it. By 3,000 BCE in France, there is clear proof of organized salt production using special ceramic pots for heating brine.

In China, people were making a lot of salt by 1,000 BCE, mainly by boiling salty water. Along the Chinese coast, ancient sites show sea-salt production adapted to changing coastlines. In India, the ancient Harappan site of Padri (around 2200–2000 BCE) was likely a special center for making sea salt. In ancient Mesopotamia (including Sumer), people got salt from natural salty areas and marshlands. In America, at El Salado in Mexico, salt production happened in two main periods: around 1400–1000 BCE and again around 650–1000 CE.

By classical antiquity, large marine salt ponds (called salinae) were used around the Mediterranean Sea. Seawater was guided into connected, shallow ponds. The water slowly became saltier in each pond until the salt crystallized and could be collected. Salt production was very important in ancient times for food preservation, raising animals, and crafts. Ancient texts also show that salt had special meaning in rituals, laws, and symbols across the ancient Near East. It was used in offerings, treaties, and even to curse lands. Early Christian writings used salt as a metaphor for goodness. Roman salt ponds have been found in places like Spain, Turkey, and near Rome. Along Israel's Mediterranean coast, ancient salt-producing sites with shallow evaporation basins and channels have also been discovered. In Oceania, ancient solar-evaporation salt pans were found at the Sigatoka Sand Dunes in Fiji, dating back to the seventh century CE. People used large clay dishes to evaporate seawater there.

Salt Making in the Middle Ages

During the Middle Ages, especially along the French Atlantic coast, people started building special solar salt ponds. In areas like Guérande, these pond systems were well-established by the 9th century and became the main way to make salt.

Outside France, medieval salt ponds were also common. In England, the Domesday Book from 1086 listed over 1,195 "salinae" (salt pans), mostly along the southern and eastern coasts. In Portugal, records from 959 mention salt pans at Aveiro.

From Medieval Times to Today

After the Middle Ages, European salt making continued to grow. Coastal solar salt ponds became even more common, and inland salt works became more efficient. For example, the Piran/Sečovlje salt system in the northern Adriatic Sea was reorganized under Venetian rule. It became very successful and continued to operate for a long time.

Gallery

See also

Kids robot.svg In Spanish: Salina para niños

  • Solar desalination
  • Seawater greenhouse
  • Evaporite
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