East Asia: Widespread water deficits to emerge in SE China

28 January 2021

THE BIG PICTURE
The 12-month forecast for East Asia through September 2021 indicates widespread water surpluses of varying intensity in the Yellow (Huang He) River Basin, reaching exceptional intensity in parts of Shaanxi and Gansu. In the Yangtze Basin, primarily moderate surpluses are forecast for the river’s middle and upper regions, with some deficits in the far reaches of the upper basin.

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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 Southeast China, deficits are expected, mild to moderate overall but more intense along the coast and in Taiwan. Moderate to severe surpluses are forecast in the central Pearl River Basin between the Hongshui and Rong tributaries. On the southern coast, surpluses will be extreme to exceptional in Guangdong’s Leizhou Peninsula and nearby in Hainan.

Tibet (Xizang) can expect a complicated patchwork of water conditions including surpluses in the center of the region, pockets of deficit in the east and west, and some areas in transition. In China’s vast northwest, intense deficits will dominate Xinjiang Province along with some transitional conditions. Deficits will reach into Qinghai, northern Gansu, and western Inner Mongolia.

Deficits are forecast in south-central and northwestern Mongolia, surpluses in the east and far north. Surpluses are expected in North Korea and will be extreme in the region north of Pyongyang. Moderate deficits are forecast for South Korea, and moderate to severe deficits for Hokkaido and central Honshu, Japan.

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

The forecast through March 2021 indicates that surpluses will remain widespread and intense in Northeast China dominating a vast area from the Russian border to the Bohai Sea. Surpluses will also remain widespread in the Yellow and Yangtze River Watersheds. However, surpluses will shrink south of the Yangtze in the middle portion of its basin, and the extent of exceptional deficits will shrink overall. Exceptional surpluses are forecast between the Hongshui and Rong Rivers, tributaries of the Pearl River, with transitional conditions to the south and exceptional surpluses picking up again in Guangdong’s Leizhou Peninsula and nearby Hainan.

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Widespread moderate to severe deficits will emerge in southeastern China while deficits in Taiwan moderate. Some pockets of moderate deficit are forecast in Yunnan. In Tibet, surpluses are forecast south of the Yarlung River (Brahmaputra) topped by a layer of deficits north of the river. Deficits are also forecast in western Tibet, surpluses in the central region, and transitions in the east. Widespread deficits will dominate much of Xinjiang in northwestern China and will be particularly intense in the Kunlun Mountains, but surpluses are forecast in the province’s northern regions. On the Korean Peninsula, exceptional surpluses will persist in the north and intense deficits will emerge in the south. In Japan, surpluses will retreat from Shikoku and deficits will intensify in eastern Honshu.

From April through June 2021, surpluses will persist in the Yellow River Basin and retreat from the Yangtze Basin. Surpluses in Northeast China will shrink but remain widespread and intense. Deficits in southeastern China will shrink but persist with intensity on the coast, retreating altogether from Taiwan. Deficits will also retreat from Yunnan and moderate surpluses will emerge. Anomalies in Tibet and in northwestern China will shrink. Surpluses will nearly disappear in North Korea and deficits in South Korea will shrink and moderate. In Japan, moderate to severe deficits are forecast for northern Honshu and Hokkaido.

The forecast for the final three months – July through September 2021 – indicates normal conditions in many areas of East Asia with surpluses in Northeast China and scattered pockets in the Yellow River Watershed. Deficits are forecast in northwestern China and surpluses in western Tibet.

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

IMPACTS
Despite recent rainfall, water storage in Taiwan’s Shimen Reservoir is insufficient to supply irrigation to paddies in parts of Taoyuan, prompting officials to suspend piped water for the spring harvest. To insure sufficient public supply, the suspension will last from 6 January through 21 February, affecting around 28,000 hectares (~69,000 acres) of arable land.

Heavy snowfall along the Sea of Japan left 13 dead, 250 injured, and 1,200 vehicles stranded on the Hokuriku Expressway in Fukui Prefecture, Japan. In Toyama Prefecture, 200 vehicles were stranded on the Tokai-Hokuriku Expressway, and 250 people were stuck on Niigata Prefecture's National Route 8.

Damages from China’s 2020 June through October flooding cost around $32 billion, according to estimates by a global charity organization.

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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