Analysis of the rainstorm and flood of 2003 in the Huaihe River Basin
Zhao Jin

Qian Mingkai

Xu HuiCheng Xingwu Xu Shijin(Huaihe River Commission, MWR, Bengbu, 233001 Anhui, Chinazhaojin@hrc.gov.cn)
Abstract: In the Meiyu period from June 20 to July 21 in 2003, a wide, heavy and lasting rainstorm occurred in theHuaihe River Basin as the complex result of synoptic system, caused a flood with a high water level in the main streamof the Huaihe River and its tributaries at the same time. The main stream of Huaihe River rose its the warning level, thehighest water levels for the reaches from Zhengyangguan to Huainan were higher than that in history and created therecorded ones. The maximal discharges in the reaches of downstream from wangjiaba were more than those in 1991.
This paper analyzed on the characteristics of the weather, the meteorological causation about the heavy rain, andthe condition of incident precipitation and subsequent discharge. The paper expatiated upon the conditions of the floodof 2003 by using the achievement of the restoring computation of runoff of the flood, comparing with the conditions ofthe historic flood (for example the flood of 1954 and 1991) in Huaihe River Basin. The result indicated that themaximal water quantity in moving 30 days and 60 days at main stations of the stream of the Huaihe River was about
once per 10~30 years (i.e. the return period is 10~30 years) respectively. It concluded that the flood of 2003 in HuaiheRiver Basin was the second largest since 1949 and it was less heavy than that in 1954.
Key Words: Huaihe River Basin Rainstorm and Flood
1Introduction
The Huaihe River Basin (HRB) is situated in the east part of China. It rises of the Tongbo and Funiu Mountains inwest, and faces to the Yellow Sea in east. It takes the south dike of the Yellow River and the Yimeng Mountain as
northern boundary, and the Dabie Mountain、the Jianghuai hill、the Tongyang canal and the Rutai canal as southernboundary. HRB totally covers 270,000km2 in area. The Huaihe River originates from the Tongbo Mountain of Henan
province and flows through four provinces, namely Henan, Hubei, Anhui and Jiangsu. Totally it is 1000km long and its
main stream empties into the Yangtze River at Sanjianngying of Jiangsu province. The Hongru River, the Shaying Riverand the Guo River are in the north of HRB, the Shiguan River and the Pi River are in the south. They all run into theHuaihe River as the major tributaries. There are many lakes in HRB such the major lakes as the Hongze Lake and theNansi Lake. HRB is located in the climate transition zone from north to south in China so that the climate is changed
acutely there. Into flood season, the floods occurred from mountains of the upper reaches of the Huaihe River quickly
run into the middle reaches. But the floods pass slowly and cannot be discharged on time in the middle reaches because
the declivity changes gradual. Thus the disaster of the flood is easy to be led once there be the rainstorm.So far the floodin 1593 is the biggest one in HRB by the historic recordation. Since the 20th century, there have occurred the rainstorm
and flood many times in HRB. And the bigger floods in 1954, in 1991and in 2003 are typical ones over HRB.
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Meteorological causation and synoptic characteristics
In 2003, the greatest flood had taken place in HRB among the flood season since 1954. The flood peak discharge
and flood level of the main river considerably exceeded the record set since 1949. According to the precipitation, theMeiyu period around HRB is defined as rainy period from June 20 to July 21,2003, the process of heavy rainfall can bedivided into five stages, the first stage is 20 to 23 June, the 2nd stage is on 25 to 26 June, the 3rd stage is from June 29
to July 5, the fourth stage is in 8th—12th and last is 19th –21st July. The flood-causing rainstorm occurred in three periods,
which were from June 29 to July 5, on July 8 –12 and from 19 to 21. The characteristic of heavy rainstorm in 2003 iswidespread area, long duration, uneven in spatio-temporal, stronger intensity and large amount of total.
During flood season around Yangtze-Huaihe river basin in 2003, the main circulation pattern of two ridges and one
trough was prevailing around Eurasia between in the middle and high latitude, especially from 20th June to 5th July. One
blocking high was located at the Ural mountain in Russia, another blocking high was located at the Okhotsk Sea,
(Fig.1), that is typical pattern of two ridges and one tough. The cold air from the Baikal Lake moved farther eastward
1and southward to HRB. The subtropical high of the west Pacific Ocean moved every now and then between 18ｏN-24ｏN
among June to August, but it markedly strengthened and become more stable during June 20 to July 5 and July 8 to21,as well as its ridge was between 21ｏN-24ｏN, HRB was influenced by the northwest edge of the house high, thatsituation led to the Yangtze-Huaihe Meiyu front to be stationary around HRB and persistent rainfall. This circulation
feature is the same as the flood season in 1991.The main factors result in heavy rainstorm in HRB included synopticsystems, such as the low-level southwest jet and Yangtze-Huaihe shear line, as well as meson-scale systems, such as

Fig.1 Contour chart at 500hPa on June 30

Fig.2 Synoptic chart at 850hPa on July 1

low vortex. As generally speaking, the low level southwest jet at 850hPa set up before heavy rain (Fig.2), it transported
a lot of moisture from Bay of Bengal to Yangtze-Huaihe river basin. During the period of flood-causing torrential rain
(June 29 to July 5, July 8 to 12), the shear line appeared at both 850hPa and 700hPa, and quasi-stationary. The heavyrain would stop when the shear line weakened or disappeared. The low vortex is the meson-scale system that lead tostrong heavy rainstorm directly in the Huaihe river, there were nine low vortexes among June to July and influenced
Huaihe river, they often formed over southwest part of China, then moved eastward along the shear line, when theyreached the Huaihe river region and become stronger, which resulted in persistent heavy rainstorm.

3The conditions of rainfall, flood and disaster
3.1 The conditions and characteristics of rainfall
It was the Meiyu period over the Yangtze-Huaihe River Basin from June 20 to July 21 in 2003. ( Fig.3) Due to theMeiyu front over there was quasi-stationary; five wide rainstorms were occurred in HRB. The major rainfall lied on thearea along the Huaihe River, the Dabie Mountain, the middle and lower reaches of the tributaries on the north of theHuaihe River and the partial Lixiahe area. The rainfall of the stage from 28 June to 5 July was the heaviest, the mostlasting and the most concentrative one in 2003. Maximum precipitation was 546.0mm occurred at the Taihe station ofthe Ying River and 534.6mm occurred at the Huji station of the Quan River. So that the first flood of HRB in the flood
50.0
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
19-Jun22-JunFig.3

25-Jun28-Jun

1-Jul

4-Jul

7-Jul

10-Jul13-Jul16-Jul19-Jul

22-JulDaily precipitation in M eiyu period of 2003 on Huaihe Water System2season of 2003 resulted from this rainfall.
It was the Maximum of the accumulated rainfall for moving 30days from 20 June to 21 July in 2003 (Fig.4). The
total rainfall in Dabie Mountain, the partial middle reaches of the Shaying River and the north area of the Hongze Lake
was more than 800mm. The precipitation was 940mm at the Liulaojian gate of the Lixiahe area, 937.3mm at theQianfan station of the Dabie Mountain and 879.4mmat the Guanji station of the Ci River.
The characteristics of rainfall of 2003 in HRB were: (1) lasting, and more concentrated on the time, (2) wide, but
uneven in spatio-temporal, (3) heavy, and the gross of precipitation being greater.
8000the Wangjiaba station
the Lutaizi station

7000

6000

5000

4000

3000

2000

1000

019-Jun 28-Jun 7-Jul 16-Jul 25-Jul

Fig.4

Isohyets during 22 June to 21 July 2003 in HRB

Fig.5

3-Aug 12-Aug 21-Aug 30-Aug 8-Sep 17-Sep 26-Sep

5-Oct 14-Oct 23-Oct 1-Nov 10-Nov

Daily discharge at the Wagjiaba and Lutaizi station in flood

3.2 The conditions and characteristics of flood
The rainfall resulted of eight floods in the middle reaches of the Huaihe River since onset of Meiyu. (Fig.5)
Through Henan, Anhui and Jiangsu provinces (about 750km long) at the major stations in mainstream as Xixian,Wangjiaba, Zhengyangguan, Bengbu, Hongze Lake and the stations in tributaries as the Huang River, the Hongru River,the Shiguan River, the Pi River, the Shaying River, the Guo River and so on, the water lever were about 0.16-3.35m
higher than the warning lever. The lever at the Wangjiaba, Zhengyangguan, Lutaizi station in the mainstream and thepartial stations of tributaries as the Pi River, the Hongru River, the Shaying River was 0.02-1.47m higher than theassuring lever. The peak water lever at the stations of Wangjiaba, Zhengyangguan, Bengbu and Zhongdu were 29.42m,26.80m, 22.05m and 14.37m. And at these four stations the peak water lever were 6th, 1st, 2nd and 2nd and the peakdischarge were 7th, 5th, 3rd and 2nd respectively since the found of the P.R.China. The peak discharges of the partial
tributaries were greater than that in history. According to the frequency analysis on the maximum flood magnitude ofmoving 30 days, the return periods decrease from upper to lower: 11years for the flood event at Wangjiaba, 23 years atBengbu and 29 years at Zhongdu station.
The characteristics of flood of 2003 in HRB were as follows: (1) the flood ran fast and high water lever was lasting,(2) the flood was higher water lever and greater discharge, (3) the flood met the rainfall so that the flood was occurredin the main reaches of the Huaihe River and its tributaries at the same time.
3.3 The conditions and characteristics of disaster
The rainstorm and flood of 2003 came into being the severe disaster in Henen, Anhui and Jiangsu provinces. There were
37.3×106 people in the disaster, 770×103 houses collapsed and 3.847×106 cropper being waterlocked. Those directcaused the RMB:28.6 ×109 economical losses.
The characteristics of disaster in 2003 were : (1) no man died because of the flood storage areas and flood detention
areas operation, (2) the waterlocked areas were not wide, (3) the economical loss was not great correspondingly.
4Comparison with the historic floods (in 1954 and in 1991)
4.1 Comparison the rainfall of 2003 with that of 1954 and 1991
The Maximum of accumulated rainfall for moving 30 days in 2003 compared with that in 1954 and in 1991 was little,and less than 1000mm. But maximum in 1954 and in 1991 was more than 1200mm. It indicated that the rainfall inpartial areas in 2003 was no heavier than in 1954 and in 1991. The area of the precipitation being more than 400mm in2003 was all narrower than in 1954 but wider than in 1991. But the area of the precipitation being more than 900mm in3

2003 was narrower than in 1954 and in 1991. The precipitation gross of the maximum of the accumulated rainfall formoving 30days in 1954, in 1991 and in 2003 were 981.7 ×108m3, 788.7×108 m3 and 959.2×108m3 respectively. Thus
the gross in 2003 was about 2.3 percent less than in 1954 and about 30 percent more than in 1991.
The mean precipitation for moving 30 days in 2003 was 475mm, 516mm in 1954 and 389mm in 1991. So it
indicated that the mean precipitation in 2003 was 8 percent less than in 1954 and 22 percent above in 1991.The mean
precipitation in 2003 in major areas except for the Lixiahe area was less than in 1954 and more than in 1991. (Table.1)
Table.1 Precipitation at the major areas of the Huaihe Water System in 1954, in 1991 and in 2003（unit：mm）
Area

Days

In 1954 In 1991 In 2003

No.1

RemarkHuaihe Water System

30516389475

In 1954

1991< That inWangjiaba

30623395471

In 1954

1991< That in 2003 < 1954

Zhengyangguan

30566380440

In 1954

1991< That in 2003 < 1954

Bengbu30533374438

In 1954

1991< That in 2003 < 1954

Zhongdu30

514378454

In 1954

1991< That in 2003 < 1954

Lixiahe area

30550

637592

In 1991

2003 < 1954

1954< That in 2003 < 1991

4.2

Comparison the flood of 2003 with that of 1954 and 1991
In 2003, the maximum discharge at the major stations of the Huaihe River was 1,230-5,120m3/s less than that in1954. and as well less than in 1954 at the main tributaries such as the Shaying River and so on. According to thefrequency analysis on the flood magnitude, the maximum of moving 30 days, 60 days and 120 days in 2003 were lessthan in 1954, and their frequency of 2003 were less than that of 1954 at the same. (Table.2)
The peak water lever and discharge of 2003 at the control stations of the lower reaches from the Huaibin station
were higher and greater than that of 1991. The water lever of the watercourse to Yangtze and the Lixiahe area aroundthe Hongze Lake in 2003 was higher than in 1991. Compared the flood magnitude at the major stations of the mainstream in the flood season of 2003 with which of 1991, the discrepancy of them was not large. The maximum ofmoving 30 days in 2003 was above in 1991, but the maximum of moving 60 days was udder in 1991 by the frequency
analysis on the flood magnitude. Otherwise there were 17 flood storage areas or flood detention areas operation in
1991,but only 9 areas operation in 2003.
Table.2 Return period of the Huaihe Water System in 1954,in 1991 and in 2003

StationsWangjiaba

Runheji

Zhangyangguan

BengbuZhongduIn 1954404851

56

68

In 1991

913121318

In 20031113152329

In 195432423740

In 1991

11111214In 2003

99101324

2122151824

Return period

30 days

60 daysIn 1954

120 days

In 1991
In 2003

Analyzing on the comparison the rainfall and flood in 2003 with that in 1954 and in 1991, it concluded that therainstorm and flood of 2003 in HRB was heavier than that of 1991, but less heavy than that of 1954. So it was thesecond largest flood in HRB since 1949.
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