Mon, Mar 10, 2003 - Page 8 News List

It's time to think of droughts as normal

By Fan Kuang-lung 范光龍

Because El Nino was so evident last year, it is very possible there will be a drought this year. The government should immediately implement water-conservation measures.

Normally, the equatorial trade winds in the Pacific Ocean blow toward the west. These winds carry warm surface water to the west Pacific. A large portion of the western Pacific has a sea surface temperature of over 28?C. Because tropical depressions, which beget tropical storms and typhoons, are often formed in areas with sea surface temperatures higher than 27?C, most of them occur in the tropical region of the western Pacific.

There are an average of 27 typhoons per year. Each year, typhoons strike Taiwan 3.7 times on average. As the trade winds blow warm surface water to the west Pacific, the sea level in the western Pacific is 60cm to 90cm higher than that in the eastern Pacific.

Statistics show that El Nino, on average, happens once in two to five years and its strength varies each time, meaning that it has more to do with the yearly cycles of currents and trade winds. El Nino's effect on this country is notable because it causes fewer typhoons to hit the western Pacific -- although they are stronger ones. This is because the area where El Nino would have formed actually moves toward the east, sending the source of typhoons that hits Taiwan further away.

The frequency of typhoons striking the country, therefore, decreases because they have more places where they may roam -- and this gives Taiwan less rainfall. But, those typhoons coming from seas further east, having more time to build up strength, are more apt to form into medium or high strength typhoons. Strong winds and abundant rainfall increase the possibility of landslides in mountainous regions and floods in urban areas.

Records show that flooding in Taipei is more serious when the El Nino phenomena takes place. Those years in which El Nino occurs, we should take extra precautions to prevent disaster and damage.

The phenomenon of El Nino was evident last spring. There was little downpour from May's "plum rain" season and only one typhoon hit the country last year -- Typhoon Nakri in July. As a result, a drought made water-restrictions necessary.

Taiwan has an abundant rainfall that very few countries in the world can match. But it is also among the top 20 of countries with water shortages. It is densely populated and its industry thirsts for water. Nearly 75 percent of rainfall is concentrated from May to October. And because of the steep terrain and a dearth of reservoirs, over 70 percent of the rainwater flows into the ocean.

So droughts should be considered the rule, not the exception. Because El Nino was so evident last year, it would be unrealistic to hope for the plum rains to bring us some relief. The government should implement water-conservation measures soon. Otherwise, the water shortage problems will become quite serious this year.

Last September, Typhoon Sinlaku passed over Taiwan's northern seas and made its landfall in China's Fujian Province, killing more than 20 people there. Many people were not gratified to have been spared from the misfortune. Instead, they cursed the Central Weather Bureau for the inaccuracy of weather forecasts. But people must ask themselves: "Have I done everything I can to guard against disaster?"

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