East Asia: Water surpluses to persist between Yellow & Yangtze

20 September 2021

THE BIG PICTURE
The 12-month forecast for East Asia through May 2022 indicates widespread extreme to exceptional water surpluses in Northeast China in the vast Songhua River Watershed and extending north to the Russian border. Surpluses of varying intensity are expected throughout the North China Plain, along the Lower and Middle Yellow (Huang He) River, and in the river’s upper basin.

In the Yangtze Basin, surpluses will be widespread throughout the Basin with exceptional surpluses in the lower watershed and the nearby Fuchan River watershed. Surpluses will also be exceptional in a vast area from Chongqing north into Shaanxi, and along the Min, Dadu, and Tongtian Rivers.

East_Asia_Composite_Adjusted_202106-202205_12mo_twitter.png

In South and Southeast China, deficits are forecast in eastern Guangdong, Guangxi, southern Fujian, and southern Jiangxi. Anomalies will be exceptional in Guangdong. Exceptional deficits are also forecast from western Inner Mongolia through northern Gansu. Deficits of varying intensity are expected in eastern Xinjiang, surpluses in the west, and transitional conditions in the Tarim Basin. Much of Tibet (Xizang) will see surpluses with severe to exceptional anomalies tracing the Yarlung (Brahmaputra) River.

Taiwan can expect moderate deficits in its northern tip and moderate surpluses along the southwestern coast.

In Mongolia, normal conditions are expected in Ulaanbaatar and deficits west of the city. Surpluses are forecast in many pockets in the nation’s eastern half and in the north where anomalies will be intense around Lake Khövsgöl.

Nearly normal conditions are forecast for the Korean Peninsula with some intense surpluses in the northeast. Exceptional deficits are expected in Hokkaido, Japan; mild to moderate deficits in northwestern Honshu; and surpluses of varying intensity in remaining regions of Japan.

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

The forecast through November indicates that surpluses will remain widespread and intense in Northeast China though the extent of exceptional anomalies will shrink north of the Heilongjiang River and deficits will emerge in Jilin. Severe to exceptional surpluses will persist in the North China Plain and Lower and Middle Yellow River Watershed, while surpluses in the Upper Basin shrink and downgrade. Widespread surpluses will also persist in the Yangtze Basin with extreme to exceptional surpluses in the Lower Basin and along parts of the river’s path. Deficits in Southeast China will downgrade though anomalies in Guangdong will be severe to extreme. In the south, deficits will retreat from Hainan but increase and intensify in Guangxi. Moderate surpluses will emerge in western Yunnan as deficits retreat. Intense deficits from western Inner Mongolia into Xinjiang will downgrade, leaving some lingering mild to moderate anomalies. Transitions will increase in the Tarim Basin, and surpluses will continue in much of Tibet.

East_Asia_Composite_Adjusted_202106-202205_3mo_twitter.png

On the Korean Peninsula, deficits will retreat, and surpluses are forecast in the far northeast and the coastal south. Surpluses will remain widespread from central Honshu through southern Japan, intensifying along parts of the southwestern coast. Deficits will disappear from northern Honshu but will persist with intensity in Hokkaido, shrinking slightly in southern regions.

From December 2021 through February 2022, surpluses will remain widespread and intense in Northeast China though moderate deficits will increase in Jilin. Surpluses will persist in the North China Plain; Lower Yellow River Basin and eastern Qinghai in the Upper Basin; and Lower and Middle Yangtze Basin, downgrading as stretches of the Yangtze moderate. In South and Southeast China, severe to extreme deficits will persist in Guangdong and Guangxi, with mild to moderate deficits elsewhere. Surpluses will shrink in Yunnan. Deficits will increase and intensify in eastern Xinjiang. In North Korea, surpluses will continue in the northeast. Moderate deficits will emerge in South Korea’s southern extreme. In Japan, deficits in Hokkaido will downgrade. Much of Honshu will return to normal but moderate deficits will emerge on its east coast and through the other islands.

The forecast for the final three months – March through May 2022 – indicates surpluses in Northeast China and the North China Plain. Surpluses will shrink south of the Yangtze but will persist in the Yellow River Watershed, increasing in the Upper Basin. Near-normal conditions will return to South and Southeast China, the Korean Peninsula, and southern Japan. Deficits are expected in northern Japan, Inner Mongolia and south-central Mongolia, and eastern and central Xinjiang.

Please note that WSIM forecast skill declines with longer lead times.

IMPACTS
Beijing’s 2021 flood season - June through August - was its highest in 20 years, with the region receiving about 70 percent more precipitation than average.

In late August, over 100,000 people were affected by flooding in Ankang in Shaanxi Province after the city received 171.8 mm (6.76 inches) of rainfall.

Mid-August flooding in Hubei Province claimed 21 lives after a deluge brought 20 inches of rain. Over 280,000 people were affected, 2,700 structures suffered damage, and 63 bridges were destroyed. In early September, inflows into Three Gorges Reservoir in Hubei hit 54,000 cubic meters per second. At the same time, flooding hit Chongqing in southwest China.

In Japan, at least 8 people died during August flooding that struck particularly hard in Kyushu where over 1,000 mm (39 inches) of rain fell during 7 days. Throughout the nation, many rivers overflowed and landslide damage was reported.

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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