East Asia: Widespread water surpluses will persist in China

18 August 2020

THE BIG PICTURE
The 12-month forecast for East Asia through April 2021 indicates widespread, intense surpluses in the Yellow (Huang He) and Yangtze River Basins. Conditions will include exceptional anomalies in the upper basin of the Yellow River and the northern stretch on the Ordos Loop, as well as Anhui Province in the Yangtze Basin and along nearly all of the Yangtze’s path and in its upper basin.

In Tibet (Xizang), intense surpluses are forecast along the Yarlung River (Brahmaputra) and in the western and northeastern regions of the province.

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Deficits are forecast for China’s southern provinces from Yunnan through southern Guangxi and Hainan and pockets reaching Fujian and northern Taiwan. Deficits will be intense in Yunnan and Taiwan. Some northern tributaries in the Pearl River (Zhujiang) Basin can expect surpluses along with conditions of both deficit and surplus (pink/purple) as transitions occur.

In the north, Western Inner Mongolia will see severe to exceptional deficits, conditions that will reach west into Xinjiang and the Taklimakan Desert. Some conditions of both deficit and surplus are also expected in Xinjiang as transitions occur. Deficits of varying intensity are forecast for central Mongolia and pockets of surplus in the nation’s west and far east. Northeast China can expect surpluses of varying intensity and some moderate deficits near the Bohai Sea.

On the Korean Peninsula, deficits are expected in the northeast and surpluses along the peninsula’s central east coast and in the south. Surpluses are also forecast for central and southern Japan and will be exceptional west of Tokyo. Deficits are predicted for Hokkaido.

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

The forecast through October indicates that surpluses in China will shrink and downgrade overall but will remain widespread in both the Yellow and Yangtze River Watersheds. The extent of exceptional surplus will shrink considerably though large pockets are forecast in Anhui, southern Gansu, Qinghai, western Tibet, and along the upper reaches of the Yangtze. Surpluses will moderate in Guizhou, Hunan, and much of Hubei, and surpluses in Northeast China will shrink and downgrade.

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In southern China, moderate deficits are expected from southern Guangxi through Guangdong, Fujian, Hainan, and northern Taiwan. Deficits in Yunnan, while shrinking, will remain intense.

In the north, deficits will nearly disappear in Mongolia, but widespread deficits of varying intensity will emerge in China along the northern Bohai Sea through the extreme northern areas of North Korea. Moderate surpluses are predicted for the southern portion of the peninsula, and surpluses are also forecast in Japan from Kyushu through much of Honshu but anomalies will be more intense. Moderate deficits are expected in central Hokkaido.

From November through January, surpluses in China will continue to shrink and downgrade but will persist in a vast stretch across the breadth of the nation from the northern Tibetan Plateau and upper reaches of the Yangtze through the North China Plain to the Yellow Sea. Surpluses will be exceptional in parts of Tibet, western Qinghai, and southern Gansu, and moderate to extreme farther east in Shaanxi, Hubei, Henan, Anhui, Jiangsu, and Shandong. Deficits will moderate north of the Bohai Sea, become merely mild in Southeast China, increase in the south in Yunnan, Guangxi, Guizhou, and emerge in pockets of Sichuan. Nearly normal conditions are forecast for the Korean Peninsula and Japan.

The forecast for the final three months – February through April 2021 – includes persistent surpluses from Tibet to the Yellow Sea. Areas of deficit include northwestern China and pockets of the south.

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

IMPACTS
The toll from summer flooding in China has risen to over 200 deaths and US $25 billion in damages, as torrential rainfall challenged the nation’s major river systems, the Yellow and the Yangtze. Since June, around 3.7 million people have been displaced or evacuated and 5 million hectares of cropland destroyed. The estimated economic damages are nearly 16 percent higher than the average for flood-incurred losses over the past five years.

In northeastern Japan, the Mogami River overflowed its banks in late July turning roads into waterways, submerging vehicles, and temporarily suspending rail service in Yamagata Prefecture. In mid-July, torrential rainfall in the southwestern region of the nation pushed the Kuma River above flood stage, killing 64 people including 14 residents of a nursing home. Flood damage was widespread in the Kyushu region and the federal government has promised 400 billion yen (US $3.74 billion) in aid.

South Korea’s longest monsoon in seven years - 42 consecutive days of rain - left 14 dead and 12 missing after flooding and landslides. Flooding on the Han River backed up traffic in Seoul as roads and bridges became inundated.

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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