East Asia: Surpluses on Yellow and Yangtze Rivers to diminish, surpluses to persist in Zhejiang & Fujian

October 25, 2016

The Big Picture
The 12-month forecast map for East Asia ending June 2017 (below) shows a complex patchwork of water anomalies. Deficits are forecast for a pocket in Northeast China; central and northeast regions of the Korean Peninsula; in China from the Shandong Peninsula on the Yellow Sea southwest to the Tibetan Plateau; and in eastern Yunnan. Water surpluses are forecast in China along the Yellow River, along the middle and lower reaches of the Yangtze River, north of Tibet, and in Tokyo and Hokkaido, Japan. Both deficits and surpluses are forecast in Mongolia and northwestern regions of China.

Impacts
Drought in central China's Hubei province has resulted in a shortage of drinking water for 237,000 residents, damaged 123,000 hectares of crops, and affected 170,000 head of cattle. September precipitation in the area was only 10 percent of normal, and provincial officials are concerned about the impact on this year's harvest.

Much farther north, this summer's drought in the Hulunbuir grasslands of China's Inner Mongolia - exacerbated by record high temperatures - has sheep herders in debt and facing losses. A reduced hay harvest has left them with insufficient winter feed, and in August several herders were injured and dozens of sheep killed in a dispute over grazing lands. Over the last two decades a bigger picture has emerged in which the combined forces of climate change, overgrazing, and pollution have led to severe degradation of the grasslands.

Heavy rain from Typhoon Megi caused flooding and landslides in Taiwan and in Zhejiang, Fujian, and Jiangxi provinces. Parts of Fujian recorded 800 mm (31.5 inches) of rain between September 27th and 30th, according to China's Ministry of Civil Affairs. Four people died in Taiwan, five in Fujian, and six in Zhejiang, with dozens more unaccounted for and presumed dead. Around 15,000 people were evacuated in Taiwan. More than 10,000 homes were damaged in Zhejian, Fujian, and Jiangxi, and 900 homes were destroyed.

Forecast Breakdown
The 3-month maps (below) show the evolving conditions in more detail.

The October through December map shows a transition from deficits in Northeast China to near normal conditions, and diminished severity of deficits on the Shandong Peninsula. Though the extent of exceptional deficits in Yunnan and Guangxi is forecast to shrink somewhat, deficits are forecast to emerge from that region in a line leading north to Sichuan. Surpluses on the Yellow River are expected to diminish in extent, as will surpluses on the Yangtze. However, surpluses will continue to emerge in Zhejiang, Fujian, and southern Taiwan, increasing in extent and severity. Surpluses in Hokkaido, Japan are forecast to become less severe, transitioning from exceptional to moderate; moderate surpluses will emerge in Honshu.

Most noticeable in the January through March forecast is the near absence of the widespread water surpluses that have dominated the Yellow and Yangtze River watersheds in recent months, leaving only a pocket of moderate surplus near Nanjing, Jiangsu. Deficits are forecast to persist from the Shandong Peninsula southwest to Sichuan and south from there to Yunnan/Guangxi, but the severity of deficits will be primarily moderate with pockets of extreme deficits rather than exceptional. Deficits on the Korean Peninsula are expected to linger though the extent and severity should diminish somewhat.

After March surpluses are forecast to emerge on the Yellow River and in the Tibetan Plateau.

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