Heavy Rain Threaten Crops and Cities in the Yangtze River Basin

• Rainfall has been heavier than normal in July across central China.  This followed a month of excessive rain and flooding in southern China during June.
• The rain led to landslides and flash floods that killed hundreds of people and caused billions of dollars in damages.
• Water levels in the Yangtze River and its tributaries reached the highest level since 1998, when catastrophic floods killed thousands of people in the region.
• The largest city endangered by floods is Wuhan, Hubei province.  It has a population of more than 9.0 million.
• The Three Gorges Dam on the upper Yangtze River has been very effective in controlling the river and preventing downstream flooding. So far, only a few small dikes have failed, and the major dikes along the Yangtze and other rivers are intact.
• China is now entering the peak tropical storm season.  Two storms have landed in southern China this month, causing additional damage and loss of life. 
•  The Chinese government estimates that 400,000 to 800,000 hectares of crops have been destroyed by flooding this year, with a significantly larger amount of crops hurt by excessive rainfall and water-logging.  The crops most likely affected are early rice (mature/harvest stage), single rice (vegetative/heading stage) and cotton (budding/flowering stage). 

National summary

As of July 28, floods in China this year had left 928 people dead and 477 missing.  Floods had affected a total of 134 million people in 28 provinces, municipalities and autonomous regions, causing a direct economic loss of 176.5 billion yuan (26.04 billion U.S. dollars), said the State Flood Control and Drought Relief Headquarters (SFDH).  A total of 875,000 homes had collapsed, 9.61 million people had been evacuated and 8.76 million hectares of crops had been flooded nationwide, according to the SFDH.

Weather summary

Rainfall in many parts of China has been much heavier than normal in July 2010.  The most concentrated rainfall was reported in mountainous areas of Sichuan, northern Hunan, eastern Hubei, and near the Jiangxi/Anhui border.  Rainfall amounts in these areas have exceeded 500 millimeters (20 inches).  Property damage from landslides, flash floods, broken dikes, and rising water has been extensive.   Soil moisture is very high in the Yangtze basin and most of southern China from the weeks of heavy rain, so any additional rainfall will likely cause additional flood risks. 

                     Total Rainfall, July 1-26, 2010

Although the heaviest rain in July was located in central China, rainfall was also heavier than normal in northeast China (Jilin and Liaoning) and southwest China (Yunnan).  There are reports of damage from flash floods and high water in these areas as well. 

                  Total Rainfall, July 1-26, 2010

The distribution of rainfall in the Yangtze basin itself has not been uniform.  Very heavy rainfall in the mountainous areas of Sichuan, Shaanxi, and Hunan caused local rivers and reservoirs to swell to near-record levels, and this water has now flowed into the Yangtze river itself, threatening major downstream cities such as Wuhan (Hubei province).  Very high rainfall was also reported in the Wuhan area and at the Anhui/Jiangxi border near Poyang Lake.  The total rainfall in July is the highest since 1996 in Hubei and southern Anhui.  Elsewhere in the region, rainfall amounts, though higher than normal, were similar to other recent years. 

Rainfall in the Yangtze basin was near to above normal in the spring, but much above normal in the first 20 days of July.  The heavy rain caused the Yangtze and its tributaries to rise to the highest level since 2000.

High Flood Danger in the Yangtze River Basin

Floods have hit 27 provinces and municipalities since the start of the 2010 flood season in April, affecting 110 million people, according to the State Flood Control and Drought Relief Headquarters and the Ministry of Civil Affairs.  More than 7 million hectares of farmland were affected and 645,000 houses were destroyed.  Direct economic losses had reached 142.2 billion yuan (20.88 billion U.S. dollars).  These figures include flood damage in southern China during May and June as well as the losses from the July storms.

The scale of the rainfall and flooding this year has recalled the catastrophic 1998 Yangtze River floods in which 4,150 people died and 18 million were evacuated.  (Special report - Flooding in China, Summer 1998, NCDC/NOAA).  However, government officials report that the threat of major flooding remains lower than in 1998, though some sections and lakes are approaching or have exceeded warning levels.  The construction of the Three Gorges Dam and other flood control improvements since then has helped to prevent a repeat of that disaster.  To date, flood waters have overtopped several small reservoirs and officials have deliberately breeched a handful of dikes to prevent downstream flooding.   

Three Gorges Dam - Source:  Xinhua

On July 28, China's Three Gorges Dam was tested by the highest water flow of the year.  Flow rates as high as 56,000 cubic meters per second hit the dam at 8 a.m. Wednesday, and the dam discharged water at a rate of 40,000 cubic meters per second, meaning water continued to accumulate in the reservoir.  The water level in the reservoir had risen to 158 meters above sea level at 8 a.m. Wednesday, about 17 meters below its maximum capacity of 175 meters.

Thousands of soldiers, emergency workers and residents are on guard at dikes near Wuhan, the capital of Hubei Province, as flood peaks of the mainstream of the Yangtze River and the Hanjiang River, the Yangtze's longest tributary, were expected to converge in Wuhan on Thursday, July 29.  The city has a population of about 9.1 million and is a major transport and economic hub in central China. The level of Hanjiang River, the highest in two decades, rose to 35.39 meters as it approached Wuhan at midday Wednesday.  Authorities are considering a plan to divert water from the Hanjiang River to an emergency reservoir for the first time since 2005, sacrificing thousands of hectares of farmland and fishponds to protect the dikes around Wuhan and other cities downstream.

 Weather Forecast – through August 4

The latest precipitation forecast by the Climate Prediction Center calls for moderate to heavy rain (1-3 inches) to continue in the Yangtze basin, adding more water to the already-saturated soils and brimming rivers.  Lighter rainfall in the coming week should benefit early rice harvesting/late rice planting in southeast China and the development of cotton, corn, and other summer crops on the North China Plain. 

On July 27, China Meteorological Administration published its 10-day weather forecast, which predicted moderate rain in the northern part of the North China Plain and northeast China, as well as southwest China and southeast coastal areas.  Rainfall totals were forecast to be equal or higher than normal, reaching 1 – 3 inches widely and up to 6 inches in some areas.  Temperatures are expected to be higher than normal for the next 4 to 7 days over most of the country. 

The tropical storm season normally starts in July, and two moderate typhoons (Chanthu and Conson) have already come ashore in Hainan and Guangdong.  The China Meteorological Administration said six to eight more typhoons are expected to land later this year. 

Impact on Rice and Cotton

The seven provinces located in the Yangtze river basin account for about 58 percent of China’s total rice output and 21 percent of total cotton output.  The region is also an important producer of peanuts, rapeseed, wheat, tea, vegetables, and other cash crops.  Rapeseed and wheat had already been harvested when the excessive rain arrived in July and thus were not directly affected.  The cotton crop, planted a week or two behind schedule in June, was in the vegetative/early reproductive stage.  The early rice crop (grown mostly south of the Yangtze) was ripening and nearly ready for harvest, while the single rice crop (grown in Sichuan and north of the Yangtze) was in the vegetative/heading stage.

Source:  National Bureau of Statistics

Rice

On July 21, the China Grain Reserves Corporation (formerly known as Sinograin) reported that China’s rice output could fall by 10 to 20 percent due to torrential rains, flooding, and the outbreaks of pests and diseases in the Yangtze River basin.  The quality of rice in storage was also threatened by flooding this year.  The report didn’t make clear if the estimated yield reductions referred to the entire 2010/11 rice crop or just the early rice crop, which accounts for about 16 percent of China’s total output. 

According to the Ministry of Agriculture (MOA), this year's early rice development was delayed by seven to 10 days due to excessive rain and in May and June.  Harvesting normally takes place from mid to late July.  The crop was also impacted by drought in southwest China in early spring.  However, some of the projected early crop yield losses could be offset by higher planted area.  MOA reports that China has increased its acreage of double-cropped rice by 1.2% this year in an effort to ensure another bumper rice harvest for the full year. 

Late rice transplanting was delayed due to the slow development/harvest of the early rice crop.  At this early stage, it is too soon to make a yield forecast for the late crop.  It should also be noted that China managed to produce a near record rice crop of 139.1 million tons in 1998/99 despite devastating flooding in the Yangtze basin that year.

Cotton

Officials in Hubei province have reported that as of July 22, more than 176,000 hectares of cotton were impacted by heavy rain this year, with 87,750 hectares suffering damage and 11,700 hectares destroyed.  Hubei normally plants around 550,000 hectares of cotton each year.   Crop losses from flooding in June and July were also reported in northern Jiangxi, which has an annual production around 100,000 tons, and northern Hunan province (annual production averaged at about 250,000 tons.  Water logging and lodging was reported in parts of southern Anhui, southern Jiangsu, and southern Henan provinces.   However, the weather has been favorable for cotton in other areas of eastern and northwestern China and the crop appears to be growing well.  

Current USDA area and production estimates for grains and other agricultural commodities are available on IPAD's Agricultural Production page or at PSD Online