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Magazine digest -- Changhua explores untapped underground water

2011/08/26 14:40:23

Central Taiwan's Changhua County, which has been overpumping groundwater to meet local demand, has found an untapped water source that according to researchers will not lead to land subsidence.

Although Taiwan has average annual rainfall of 2,500 millimeters, uneven distribution and high density concentrated during late spring and the summer typhoon season often leads to water shortages in some parts of the country.

As a result, farms, especially rice paddies, even though they use only 16.5 percent of the overall water supply, are often forced to delay or skip a growing season.

By tapping into what is known as underflow water, the use of which has only been developed in Taiwan in recent years, Changhua Magistrate Cho Po-yuan hopes to obtain an additional 60 million tons of water to augment the annual supply.

Gan Chun-e, an emeritus professor at National Taiwan University, said research has shown that besides evaporation or leaching into the water table, some of the water from rainfall stays on the surface layer of soil.

This water, which flows horizontally above the harder layer of plow sole -- usually found two meters down -- Gan said, is the so-called underflow water.

Gan's experiments at a beach in Miaoli County since 2008 have successfully found a way to intercept the underflow water to grow windbreak forests on salty soil by building barriers in the ground.

A breakthrough in lowering the costs of building such barriers from NT$2,000 (US$68.89)-$4,000 per square meter to less than NT$100 further allows the measure to be introduced on a large scale, said Fan Shih-yi, director-general of Changhua's Department of Water Resources.

After the success of the NT$1.5 million, 50-hectare pilot project in Hsichou Township, Fan said, the county plans to introduce the technology around the Zhuoshui River's old river course, currently called the Dongluo River.

With a plan to rejuvenate the polluted river with underflow water, the county aims to improve the public's accessibility to the area, besides increasing the water supply. (Business Today 764)(translated by Kay Liu)