Seeding the way out of our continuing water problems

Taiwan is a land of water contradictions. Although we get far more water than we can use, the southern part of the island actually gives up more water to the air than it gets seven months out of the year, meaning that drought is in fact more or less normall. In recent days the government has been attempting to alleviate drought in southern Taiwan, where in some places it hasn't rained since typhoon Morakot in August of last year. Water is so scarce that in some places in southern and central Taiwan the spring rice planting was suspended. The China Post reported last month:

Although Taiwan has already entered the wet season of spring, until March 22, the total rainfall of Tainan in March is only 0.3 mm. Tainan's average rainfall in March in previous years is 35.4mm. Kaohsiung records only one mm of rainfall in March till March 22. If there is no rain before the end of March, the two areas will have the lowest amount of rain in history, according to Central Weather Bureau (CWB).

In Hengchuen (恆春), there were only 0.2 mm of rain in Feb., the second lowest amount of rain in Feb. in a century. Dawu (大武) had 11.3 mm of rainfall in Feb., the third lowest record of rainfall in Feb. since the station set up 70 years ago.

The CNA via Taipei Times described the cloud seeding attempt, which failed:

At 11am on Friday, a squad of C-130 transport aircraft released about 4,000 liters of water from an altitude of 4,500m and targeted it at the water catchment areas of Tsengwen, Wushantou and Nanhua reservoirs in Tainan and Chiayi counties. At the same time, a team from National Taiwan University (NTU) tried to seed clouds to create rain over the same areas, but neither approach worked.

The CNA report said a calcium chloride based aerosol was used in the attempt. The China Post report above noted that the problem is global warming:

Liu said the decrease in rainfall in Taiwan is influenced by the global climate change. In the past century, the surface temperature of the earth had increased by 0.6 degree Celsius and that had changed the raining patterns.

“The most pressing impact of climate change in Taiwan is the extreme rainfalls,” said Liu. “Central and southern districts of Taiwan had already suffered from draft for eight years in the last decade.”

According a research done by Liu and his team, in the last 45 years, the days with drizzles in Taiwan are halved. For central and southern districts in Taiwan, where the main water source is drizzles, would face drought much more often. And as the days with torrential rain are doubled that of 45 years ago, the risks of water hazard and landslides are also doubled.

The number of rain days annually is also declining in the north, though it is not as obvious.

REF: Wiki on cloud seeding.
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