East Asia: Water surplus to persist in Yellow, Yangtze, & NE China

23 October 2020

THE BIG PICTURE
The 12-month forecast for East Asia through June 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 severe to extreme surpluses in the lower and middle areas of the basin.

In the Yangtze region, exceptional surpluses will dominate the lower watershed and the southern portion of the middle watershed. Surpluses as well as transitional conditions (pink/purple) are expected in the river’s upper basin. Between the Yellow and Yangtze Rivers surpluses of varying intensity are forecast.

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Northeast China can expect widespread extreme to exceptional surpluses, and surpluses are expected on the Liaodong Peninsula in the northern Bohai Sea reaching well into Liaoning Province.

In southern and southeastern China, nearly normal conditions are forecast with moderate deficits in coastal Fujian but more intense deficits in pockets of Taiwan, particularly in the north. Exceptional surpluses are expected in northern Guangxi.

In Tibet (Xizang), intense deficits are forecast in the west, surpluses in the central region, and transitional conditions in the east. In China’s vast northwest, surpluses are expected in northern Xinjiang Province, intense deficits and transitional conditions in the Taklimakan Desert, and moderate deficits in the northeastern region of the province leading to exceptional deficits in northern Gansu.

Exceptional deficits are also forecast in central Mongolia, and surpluses in the east and northwest. Surpluses are forecast for most of the Korean Peninsula and will be exceptional in North Korea. In Japan, deficits are predicted for Hokkaido and pockets of central and southern Honshu and Shikoku. Surpluses and transitional conditions are forecast for Kyushu.

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

The forecast through December indicates that surpluses in China will remain widespread in the Yellow and Yangtze River Watersheds though the extent of exceptional anomalies will shrink overall and transitional conditions will replace surpluses in western Sichuan and parts of Tibet. Exceptional surpluses will remain dominant along the lower and middle reaches of the Yangtze River itself, and south of the river in Guizhou and northern Guangxi Provinces. In Northeast China, widespread extreme to exceptional surpluses will persist. Deficits in southern and southeastern China will nearly disappear, transitioning to surplus conditions in southern Guangdong and nearby Hainan. Conditions will be complicated in Tibet and Xinjiang with intense deficits increasing in western Tibet and southern Xinjiang, and surpluses in northern Xinjiang. Deficits are forecast for western Qinghai and northern Gansu. Surpluses will cover the Korean Peninsula, downgrading in the south but remaining exceptional in North Korea. Deficits are forecast in Japan with some lingering surpluses in southern Kyushu.

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From January through March 2021, surpluses in China’s Yellow and Yangtze River Watershed will downgrade. Surpluses will be severe to extreme in the Yellow River Watershed and moderate to severe in the Yangtze region with pockets of exceptional deficit in primarily the upper regions of both basins. Normal conditions are forecast for southeastern China and some surpluses in coastal regions of the south. Exceptional deficits in Xinjiang will decrease and mild deficits will increase. Widespread surpluses will persist in northeastern China. Normal conditions will return to South Korea, but surpluses will persist in North Korea, though the extent of exceptional anomalies will decrease. Some pockets of deficit are expected in Japan, and moderate surpluses will emerge in western Hokkaido.

The forecast for the final three months – April through June 2021 – indicates normal conditions in southern China and the Korean Peninsula, surpluses in the Yellow River Watershed and in China’s northeast, and deficits in Xinjiang, central Mongolia, and Japan.

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

IMPACTS
Authorities in Taiwan have instituted water restrictions due to drought. Rainfall from June through September was the second lowest recorded in over 70 years, forcing farmers in some regions to stop irrigating. Water-saving measures include reduced tap flow and limited use of outdoor water.

Widespread flooding in China over the past months affected over 70 million people, killing over 200, and caused an estimated $32 billion in damages.

Torrential rainfall hit Northeast China in September. In Heilongjiang Province, ship traffic was suspended on the Songhua River as water levels reached flood peak, threatening the metropolis of Harbin and its 10 million inhabitants. Flooding closed Harbin’s Qunli Bund Park, submerging benches and street lamps. The Nanhu Sanchang Dam in Daqing City burst, destroying 70,000 hectares of rice.

Summer and fall flooding also affected the Korean Peninsula. Rainfall in North Korea from January through September of this year was twice that of the same period in 2019. On 2 September, Typhoon Maysak destroyed over 2,000 homes and public buildings with damage to another 1,000. Limited reporting indicates that during DPRK’s rainy season from June through September, 39,296 hectares of crops were damaged, 16,680 homes and 630 public buildings were destroyed or flooded, and roads, bridges, and a dam were compromised.

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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