East Asia: Water surplus forecast in Pearl River Basin

27 April 2020

THE BIG PICTURE
The 12-month forecast for East Asia through December indicates surpluses in the Pearl River Basin (Zhujiang River) in South China that will reach extreme to exceptional intensity in Hunan near the border with Guangxi. Transitional conditions are expected in eastern Guangxi.

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Moderate surpluses are forecast in a pocket near Shanghai on the east coast. Surpluses will also be moderate along the Lower and Middle Reaches of the Yellow River (Huang River), but will be more widespread and somewhat more intense in the river’s upper basin. Moderate surpluses are expected along the path of the Tongtian River as it flows south from Qinghai through the western border of Sichuan.

Exceptional surpluses are expected in western Tibet (Xizang) and along much of the Yarlung River (Brahmaputra River).

Northeast China can also expect some large pockets of surplus, varying in intensity.

Exceptional deficits are expected in western Inner Mongolia, China. Deficits of varying intensity are forecast for the vast bulk of central Mongolia and far western Mongolia; anomalies will be severe around Ulaanbaatar. Deficits will be exceptional across much of the breadth of Xinjiang in western China, with some conditions of both deficit and surplus as transitions occur. In the south, moderate to severe deficits are forecast in Yunnan’s southern tip.

On the Korean Peninsula, a few scattered, small pockets of deficit are forecast in North Korea, including moderate anomalies around Pyongyang. Relatively normal conditions are forecast for South Korea, Japan, and Taiwan.

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

The forecast through June indicates that surpluses in the Yangtze River Basin will retreat considerably in the Lower and Middle Basin, transitioning to moderate deficit conditions in the Lower Basin. Moderate to exceptional surpluses are forecast in the river’s upper basin. Surpluses will increase in the Pearl River Basin in the south, becoming widespread, with exceptional anomalies in Guangxi between the Hongshui and Rong Rivers. Surpluses will emerge or re-emerge in the southeastern provinces of Guangdong and Fujian. Taiwan will transition from deficit to some surplus in the north. Deficits in Yunnan will shrink and downgrade considerably.

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Surpluses will persist in the Yellow River Watershed, with the intensity increasing in the Upper Reaches in Qinghai. Surpluses will shrink in Northeast China but will remain widespread. Intense surpluses are expected to persist in western Tibet and along the Yarlung River.

Exceptional deficits will increase in western Inner Mongolia, China, and will emerge in a widespread pattern in Mongolia’s eastern half while deficit conditions in southwestern Mongolia normalize. Surpluses are forecast to emerge in much of the country’s northwestern quadrant. In Xinjiang, China, intense deficits will increase in the eastern Taklimakan Desert and in northeastern Xinjiang, transitioning from surplus in the northeast.

Some mild to moderate anomalies are forecast on the Korean Peninsula: a few pockets of surplus in the northeast and some pockets of deficit near Pyongyang, North Korea and in western South Korea. Japan will transition out of surplus as deficits of varying intensity emerge in northern Honshu and in Hokkaido. Anomalies will be extreme to exceptional in Yamagata Prefecture and across its southern border.

From July through September, conditions throughout much of East Asia will become nearly normal. However, widespread moderate surpluses are forecast for the Upper Yellow River Basin and moderate surpluses along portions of the lower and middle reaches of the river through the eastern leg of the Ordos Loop. Intense surpluses will persist in western Tibet and along the Yarlung River in the west. Some pockets of moderate surplus will persist in southern China, and a few pockets of deficit will persist in Yunnan. Some deficits will also persist in northeastern Xinjiang.

The forecast for the final three months – October through December – indicates that widespread deficits will emerge in the Lower and Middle Yangtze Basin, dipping south into the western portion of the Pearl River Basin. Deficits will also emerge around the Bohai Sea. In western China, anomalies are expected to persist in a pattern similar to the forecast for July through September.

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

IMPACTS
The drought in China’s southern province of Yunnan continues, with around 1.5 million people and 417,000 large domestic animals facing drinking water shortages in mid-April, up from mid-March estimates. The provincial water conservancy reports that over 300,000 hectares of crop were damaged, 100 rivers were cut off, 180 reservoirs have dried up, and 140 irrigation wells have insufficient water. The province has allocated 546 million yuan (around US$77.1 million) for drought relief.

A drier, warmer spring and strong winds in Sichuan Province fed a wildfire that killed 18 firefighters and a forest guide. The blaze in a mountain region near the metropolis of Xichang occurred after a period of 20 days with no rainfall.

China’s Ministry of Emergency Management is urging regional authorities in the north and northeast to increase flood preparedness, warning that severe flooding is expected along several rivers including the Songhua that flows through Heilongjiang Province. At the end of March, the country’s worst tailings mine disaster in 20 years occurred when a mine dam leaked 2.53 million cubic liters of waste into the Yijimi River, a tributary of the Songhua in Heilongjiang. The local government where the mine is located suspended water intake from its water treatment plant that sources drinking water from the Yijimi.

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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