09-25-2008 15:00

This is a fine day in Daying County, Sichuan Province. Yan Changwu is pedaling a oddlooking wooden wheel machine. The wheel machine draws up a strong rope made of bamboo strips fastened to a long bamboo tube the diameter of a bowl. The tube seems to be very heavy. When the end of the tube is opened, a stream of milky water gushes out. A workman pedals the water lifting wheel machine, which lifts the water into a wooden container at the top of the bamboo shed. This is where the water is to be aired, filtered and finally put into a big pot to be boiled. The water evaporates and crystals gradually form. These crystals are the salt used daily by people in Sichuan for thousands of years.

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Yan Wuchang is practicing the oldest salt making technique with a small diameter well. These wells were ubiquitous in Sichuan Province 1000 years ago during the Song Dynasty. They’re called Zhoutong Wells. In over a thousand years, the Sichuan people have never suffered a salt shortage, even though they are far from the sea.

To make salt you must first have a brine source, which is usually found in a sea or a salt lake. Sichuan is 10,000 kilometers from the nearest salt water source. Where does the brine in Daying County come from? Why is the diameter of the well so small and the bamboo rope so long? What’s the secret under the well? To answer these questions, we first need to know how Zhoutong Wells are drilled.

This is the wooden support frame for drilling Zhoutong Wells. A round iron knife head is fixed at its end, serving as the drill bit. It looks like the head of a soldering iron and weighs over 50 kg. The driller raises it and lets it fall using a lever to punch the well bottom. This crushes rocks to create a small diameter hole. The punching continues to a depth of over 100 meters in order to reach the underground brine, much deeper than ordinary wells. The punching head opens a secret treasure underground. It’s an ancient “underground Dead Sea”.

The ancient drilling technology allowed ancient Daying residents to discover the rich reserves of salt underground. Now we’ve measured its depth to be over 3000 meters and the salt reserve is 4.2 billion tons. It’s actually a living ancient Dead Sea. It was formed by ancient geological movements. In the middle of the Triassic Period 237 million years ago, the Qinghai-Tibetan Plateau was under an ocean. Later, the earth’s crust at the west part of China began to rise. The sea water subsided continuously, and the remaining water formed an inland salt lake called Ba-Shu Lake by geologists. In later geological periods, the temperature rose greatly, and the rainfall decreased. The water evaporated and the concentration of salt increased to form a high salt inland lake like the Dead Sea in the Middle East. However, its area was much greater, reaching about 200,000 square kilometers.

An ancient Dead Sea has been buried under Daying County, containing vast quantities of brine. Ancient Chinese invented the technology of drilling Zhoutong Wells to remove resources. Now, the Zhoutong Wells have been replaced by a modern salt making industry, and only a few of them are left, representing an ancient marvel with their lonely figures.


Editor:Liu Fang