East Asia: Water surpluses in S China will retreat

19 June 2020

THE BIG PICTURE
The 12-month forecast for East Asia through February 2021 indicates widespread surpluses in the Yellow River Basin (Huang He River), primarily moderate in the lower and middle regions but more intense in the upper portion of the watershed.

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In the Yangtze River Basin, surpluses will be moderate in the lower watershed and east of Nanchang, while surpluses along the upper reaches of the river itself will be moderate to exceptional. Surpluses are also expected in the Pearl River Basin (Zhujiang River) in southern China and will be severe to extreme in northern Guangxi. Farther south in Hainan, however, intense deficits are forecast and moderate deficits are expected in southern Yunnan. Northeast China can expect surpluses as well, as can western Tibet (Xizang) where anomalies will be exceptional including along much of the Yarlung (Brahmaputra) River.

Western Inner Mongolia will see severe to exceptional deficits, conditions that will reach north well into the center of Mongolia and west through the Taklimakan Desert in Xinjiang. Some conditions of both deficit and surplus (pink/purple) are also expected in Xinjiang as transitions occur.

Nearly normal conditions are forecast for the Korean Peninsula and Japan with some pockets of moderate deficit in northeastern North Korea.

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

The forecast through August indicates that surpluses will persist in the Yellow River Basin, downgrade in the Yangtze, and retreat from the Pearl River Basin with conditions returning to near-normal. Anomalies will be severe in the region of the Lower Yellow River and will reach exceptional intensity in the upper region. In the Yangtze Basin, moderate surpluses will increase in the lower portion, downgrade to mild in the middle region and primarily moderate in the river’s upper basin. Some pockets of moderate surplus will linger in the Pearl River Basin in Guangxi. Surpluses in Northeast China will shrink. Intense surpluses will persist in western Tibet.

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In southern China, deficits in Yunnan will moderate overall. Severe deficits will increase in Hainan and nearby on the mainland in southern Guangdong. Across the north, deficits will re-emerge in western Inner Mongolia and persist in the Taklimakan Desert of Xinjiang amid transitions. Deficits in central Mongolia will shrink and moderate. Nearly normal water conditions are forecast for Taiwan, the Korean Peninsula, and Japan.

From September through November, near-normal conditions are forecast for many regions in East Asia. Surplus anomalies will form a path from the Han River Basin, a tributary of the Yangtze at Wuhan, leading northwest into Gansu and eastern Qinghai. Moderate deficits in the middle of Qinghai will connect to a wide path of intense surpluses reaching into western and southern Tibet. Moderate deficits and transitional conditions are expected in Xinjiang. In Northeast China, surpluses will persist in Inner Mongolia but shrink in Heilongjiang and Jilin. In Mongolia, severe deficits are forecast in the north-central province of Arhangay. A pocket of moderate surplus is forecast in northern Taiwan. Conditions on the Korean Peninsula and in Japan will be nearly normal.

The forecast for the final three months – December through February – indicates that mild to moderate deficits will emerge in southern and southeastern China and the Shandong Peninsula, and in pockets of Korea and southern Japan. Deficits will increase and intensify in Xinjiang and western Inner Mongolia. Surpluses are forecast in a pattern similar to the prior three months.

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

IMPACTS
Nearly half of Inner Mongolia in northern China is suffering drought, affecting over 44 million hectares in the central and western parts of the autonomous region. Spring precipitation in Wushen Banner (Uxin Banner), an administrative division in the region, measured 50 percent less than in previous years, and until 20 May there had been no precipitation for 81 days. On 7 June, a temperature of 40C (104F) was recorded in Inner Mongolia.

In late May downpours forced the evacuation of 53,000 people in Hunan, China and damaged 140,000 hectares of crops. Torrential, prolonged rainfall in early June produced flooding in many other areas of the south, affecting over 2.5 million people and resulting in direct economic losses of CNY4.04 billion (US $570 million). In Guangxi the Lijang River breached its banks in Guilin City, rising a half meter above the warning level. The Lijang was one of 110 rivers in 11 provinces that overflowed. Qingshitan Reservoir in Guangxi also overflowed, causing flooding, landslides, and power outages.

South of Guangxi many areas of Hainan are reporting various levels of drought.

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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