EAST ASIA: WATER DEFICIT FORECAST TO INCREASE IN NORTHEAST CHINA

30 May 2018

THE BIG PICTURE
The 12-month forecast for East Asia (below) indicates widespread, intense deficits reaching exceptional severity in western Inner Mongolia, stretching west through Xinjiang, south into Qinghai, and north into Mongolia. Conditions of both deficit and surplus are also indicated for these regions as transitions occur.

Moderate to extreme deficits are forecast across Northeast China. A vast stretch of Southeast China will experience deficits ranging from moderate to exceptional, including Fujian, Jiangxi, Guangdong, Hunan, and Taiwan.

A pocket of exceptional surplus is expected at the central border of Shaanxi and Shanxi along the eastern arm of the Yangtze River’s Ordos Loop. Moderate surpluses are forecast in the lower and middle reaches of the Yangtze east of Wuhan, and much farther west in eastern Qinghai. Moderate to exceptional surpluses are forecast in western Tibet and along the Yarlung River (Brahmaputra) north of Nepal; deficits are forecast for eastern Tibet.

Moderate deficits are forecast for northern South Korea, North Korea, and eastern Hokkaido, Japan. Deficits may be severe north of Pyongyang, North Korea.

FORECAST BREAKDOWN
The 3-month time series maps below show the evolving conditions in more detail.

The near-term forecast through July indicates that the extent of exceptional deficits in Mongolia, Inner Mongolia, and Xinjiang will diminish considerably though widespread deficits of varying severity are expected and a large pocket of exceptional deficits will persist in western Inner Mongolia. Moderate to severe deficits will increase in Northeast China with some areas transitioning from surplus. Moderate surpluses are forecast for much of the Yellow River. Exceptional surpluses in eastern Qinghai will begin to moderate. Widespread, intense surpluses in the Yangtze River Basin will diminish and downgrade, leaving some areas of moderate surplus. In Southeast China, the extent of exceptional deficits will shrink, but severe to exceptional deficits remain in the forecast. Hainan will transition from surplus to near-normal conditions.

Deficits will retreat and downgrade in North Korea but severe deficits will persist north of Pyongyang. Moderate surpluses will expand in South Korea, covering much of the southern portion of the country. Near-normal conditions are forecast for Honshu, Japan, but Hokkaido will transition from surplus to deficit.

The forecast for August through October indicates that water anomalies throughout East Asia will downgrade overall. Some intense deficits will persist in western Inner Mongolia and throughout Xinjiang and northwestern Qinghai. Moderate to extreme deficits will persist in Southeast China, particularly in Guangdong. Moderate surpluses in the lower and middle reaches of the Yellow River are expected to retreat completely. Moderate deficits are forecast for Northeast China, much of the Korean Peninsula, areas of Japan along the Sea of Japan, and Hokkaido.

The forecast for the final months – November through January – indicates an uptick in the intensity and extent of deficits in the region.

(It should be noted that forecast skill declines with longer lead times.)

IMPACTS
At least three people were killed in flooding caused by torrential rain in Guangxi Zhuang Autonomous region in southern China this month. The flooding also displaced 6,100 people and damaged nearly 4,500 hectares (11,000 acres) of crops.

The neighboring territory of Hong Kong, meanwhile, has had less than half the average rainfall for this time of year amid the longest heatwave for the month of May since 1963.

Below-normal precipitation levels in southern Taiwan have prompted its Water Resources Agency (WRA) to recommend first-stage water rationing. First-stage rationing entails reducing water pressure at night and suspending superfluous water use by administrative agencies and state-owned businesses. Though Taiwan is generally considered a rain-soaked state, its water supply is limited by storage capacity. With current maximum capacity of roughly a month and a half’s water requirements, Taiwan relies on regular rainfall. Erosion and silting in reservoirs have worsened matters, displacing storage by up to a third. Taiwan’s WRA is assessing the need for temporary desalination plants for the archipelago county of Penghu ahead of its peak tourism season.

Dry weather and over-exploitation of groundwater have depleted the water table in the North China Plain by six to eight billion tons each year since 2002, according to recent research.

As of mid-May, drought has affected 2.33 million hectares (5.75 million acres) of farmland in northeastern China's Jilin Province and Liaoning Province this season.

Since the late 1990s, prolonged spring-summer droughts have become more common in North China, a top grain-producing region and home to nearly half the country's population. A recent study published in the Journal of Climate describes the climatological patterns which determine these droughts. Scientists report that the drought events are driven by a transition from La Niña to El Niño - two key circulation anomalies - when preceded by a negative North Pacific Oscillation phase in winter.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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