Number of marine disasters in China in 2009

In 2009, there were storm surges, waves and red tides 132 times in China, of which 33 times caused disasters. Various marine disasters (including sea ice and Enteromorpha prolifera) caused direct economic losses of 10023 billion yuan, and 95 people died (including missing).

Compared with the average situation of marine disasters since 1989, the direct economic loss of marine disasters in 2009 was lower than the multi-year average, and the number of deaths (including missing persons) was also lower than the multi-year average (see figure 1).

Figure 1 1989 ~ 2009 Direct economic losses (100 million yuan) and deaths (including missing persons) caused by marine disasters.

In 2009, the worst-hit province was Guangdong Province, with a direct economic loss of 4.005438 billion yuan and 23 deaths (including missing persons). The provinces with serious direct economic losses are Zhejiang Province and Fujian Province, both exceeding 654.38 billion yuan.

See table 1 for marine disaster losses of coastal provinces (autonomous regions and municipalities directly under the Central Government) in 2009.

Table1Statistical Table of Major Marine Disaster Losses of Coastal Provinces (autonomous regions and municipalities) in 2009

Provinces (autonomous regions and municipalities directly under the Central Government)

The cause of the disaster

Number of dead (including missing)

Direct economic loss (100 million yuan)

Liaoning province

Storm surge, waves, sea ice

2.59

Hebei Province

Storm surge and sea ice

0.80

Tianjin

storm tide

nine

2.49

Shandong Province

Storm surge, sea ice, Enteromorpha

9.44

Jiangsu Province

Storm surge, waves

10

1. 13

Shanghai

sea wave

four

0.03

Zhejiang Province

Storm surge, waves

17

1 1.87

Fujian Province

Storm surge, waves, red tide

five

23.84

Guangdong Province

Storm surge, waves

23

40.0 1

Guangxi Zhuang Autonomous Region

storm tide

eight

0. 14

Hainan province

Storm surge, waves

19

7.89

Combination plan

—

95

100.23

This year, the main marine disaster losses in China are storm surges (including nearshore waves), among which Typhoon Morakot (including nearshore waves) caused coastal disasters in Jiangsu, Zhejiang and Fujian provinces, with direct economic losses of 3.265 billion yuan and 7 deaths (including missing); 09 15 Typhoon Jujue (including offshore waves) caused coastal disasters in Guangdong Province, Guangxi Zhuang Autonomous Region and Hainan Province, resulting in direct economic losses of 2.404 billion yuan and death 19 people (including missing).

See Table 2 for the losses of various marine disasters in 2009.

Table 2 Statistics of losses caused by various marine disasters in 2009

Types of disasters

Number of dead (including missing)

Direct economic loss (100 million yuan)

storm tide

(including nearshore waves)

57

84.97

sea wave

38

8.03

sea ice

not have

0. 17

Xiao Hai

not have

not have

blush

not have

0.65

Enteromorpha

not have

6.4 1

Beach erosion

not have

-

Seawater intrusion and soil salinization

not have

-

Salt tide invasion

not have

-

Sea level change

not have

-

Combination plan

95

100.23

Second, the storm surge disaster

(A) the overall disaster situation

In 2009, there were 32 storm surges in China's coastal areas, including typhoon storm surge [1] 10, which caused disasters for 5 times. Temperate storm surge [2]22 times, causing disasters for 3 times. The direct economic loss of storm surge disaster was 8.497 billion yuan, and 57 people died (including missing).

Characteristics of storm surge disasters in 2009: First, the number of temperate storm surge disasters is the highest since 2005; Second, the location of typhoon storm surge disasters is concentrated. Guangdong province suffered eight typhoon storm surges throughout the year, three of which caused disasters.

See Table 3 for disaster losses of storm surges (including nearshore waves) in coastal provinces (autonomous regions and municipalities directly under the Central Government).

Table 3 Disaster loss statistics of storm surge (including nearshore waves) in 2009

(2) Major storm surge disaster process

1.0908 Typhoon Morakot storm surge

Typhoon Morakot made landfall at Beibi Township, Xiapu County, Fujian Province on August 9 16: 20. Affected by storm surges and offshore waves, Fujian, Zhejiang and Jiangsu provinces suffered direct economic losses of 3.265 billion yuan.

The largest storm along the coast increased water by 232 cm, which appeared at Guantou Station in Lianjiang County, Fujian Province. There are 16 tidal stations along the coast of Zhejiang and Fujian, which increase water by more than 100cm, including 8 in Zhejiang and 8 in Fujian. There are 1 1 tide gauge stations along the coast, and the highest tide level reaches or exceeds the local warning tide level, of which Baiyantan Station in Changle City, Fujian Province exceeds the local warning tide level by 88 cm.

The affected population in Fujian Province is 6.5438+0.65 million, the farmland is flooded by 66,060 hectares, and the mariculture is damaged by 7,460 hectares, including 4,600 hectares of pond culture and 62,654 cages. Breakwater damaged 9.2km, revetment damaged17.92km, dock damaged165,438+067. 1 152 The ship was damaged. The outer dike of the Waiwenwu seawall in Changle City was damaged by about 35 meters, the wave wall was destroyed, and the top of the dike with a width of about 10 meter was shattered by huge waves. The Hongshan seawall in Yacheng Town, Xiapu County, Ningde City was damaged, and the culture in the seawall 1200 mu tidal flat was damaged. The province's direct economic loss was 654.38+98.3 million yuan.

In Zhejiang Province, 42,209 hectares of ponds were damaged, and 17474 cages were damaged, resulting in a loss of 66,473 tons of mariculture. Breakwater was damaged by 7.73km, revetment was damaged by 6.09km, and wharf was damaged 100. 920 ships were damaged. The province's direct economic loss is 1 1.85 billion yuan.

The aquaculture in Jiangsu Province was damaged by 20,262 hectares (12,830 tons); The breakwater was damaged by 40 kilometers, and 46 docks were damaged. The province's direct economic loss was 97 million yuan.

2.09 15 typhoon jujue storm surge

Typhoon Jujue landed near bei dou zhen, Taishan, Guangdong at 07: 00 on September 15. Affected by storm surges and offshore waves, Guangdong, Guangxi Zhuang Autonomous Region and Hainan Province suffered direct economic losses of 2.404 billion yuan.

There are 12 tide gauge stations along the coast of Guangdong province, where the storm surge is more than 100 cm, and the largest storm surge is 2 10 cm, which appears at Sanzao Station in Zhuhai City. The highest tide level of 9 tide stations exceeds the local warning tide level, and Sanzao Station exceeds the local warning tide level 109 cm.

33 1 villages and towns in 38 coastal counties and cities in Guangdong province were affected, with the affected population of/kloc-0 1.6782 million, three people died 13 and six people were missing. Crops affected area 1 17439.60 hectares; Mariculture loss 15900 hectares (4 1000 tons); 726 breakwaters, 624 ponds and 768 revetments were damaged. Some river and sea dikes in bei dou zhen of Taishan were washed away, and rice seedlings were flooded in a large area, which affected industry, agriculture, transportation and water conservancy. Many low-lying areas in our city were flooded, dike facilities were destroyed, and ten thousand mu fish ponds in Zhu Lei reclamation area were flooded. The province's direct economic loss was 2.393 billion yuan.

The coastal cities of Beihai, Qinzhou and Fangchenggang in Guangxi Zhuang Autonomous Region suffered 6,965,438+million people, with 283 tons of mariculture loss, 0.42 km of dike damage and 7 revetments damage. The province's direct economic loss is 0. 1 100 million yuan.

A ship in Hainan Province was damaged, resulting in a direct economic loss of 200,000 yuan.

3. "0415" temperate storm surge

On April 15, a strong temperate storm surge occurred along the coast of Bohai Sea, causing direct economic losses of 620 million yuan in Hebei, Tianjin and Shandong provinces.

The maximum storm surge along the coast appeared at Huanghua Station in Cangzhou City, Hebei Province, with a height of 176 cm, and the highest tidal level exceeded the local warning tidal level by 34 cm. The storm surge at tidal stations in Caofeidian, Jingtang Port, Tanggu, Tianjin and Longkou, Shandong Province exceeded 100 cm.

Cangzhou City, Hebei Province has 50,000 people affected by the disaster, with 7,000 hectares (1 10,000 tons) of aquaculture damaged, 3.5 kilometers of breakwater damaged and 3 revetments damaged. The province's direct economic loss is 70 million yuan.

Three people died in Tianjin, six people were missing, the breakwater was damaged by 3.7 kilometers, the slope protection was damaged by 350 square meters, and more than 630 oil wells of Dagang Oilfield Company stopped production. The city's direct economic loss was 249 million yuan.

There are 65,000 people affected by the disaster in Shandong Province, with 2,270 hectares (7,000 tons) of aquaculture damaged, 5.4 kilometers of breakwater damaged, 2 revetments damaged and 24 ships damaged. The province's direct economic loss is 306,543.8+0 billion yuan.

See Table 4 for the disaster process and losses of storm surge (including nearshore wave) in 2009.

Table 4 Disaster process and loss statistics of storm surge (including nearshore wave) in 2009

[1] Storm surges caused by tropical cyclones are collectively called typhoon storm surges.

[2] The storm surge caused by extratropical cyclones and cold air is called extratropical storm surge.

Third, the wave disaster

(A) the overall disaster situation

In 2009, there were 32 disastrous waves [1] in China's offshore waters, including typhoon waves 12 times and cold air and cyclone waves 20 times [2]. The wave disaster caused direct economic losses of 803 million yuan and 38 people died (including missing).

The direct economic losses caused by wave disasters are more than those in 2008, and the number of deaths (including disappearances) is less than that in 2008. Affected by typhoon waves, the Taiwan Province Strait and the coastal waters of the South China Sea suffered huge direct economic losses, accounting for more than 70% of the total losses.

See Table 5 for wave disaster losses in coastal provinces (autonomous regions and municipalities directly under the Central Government).

(2) The main wave disaster process

1.0903 Typhoon "Lotus"

Tropical storm 0903 "Lotus" was generated in the South China Sea on June 8, 2009 14. On June 22nd, huge waves and wild waves ranging from 4.0m to 6.0m appeared in the Taiwan Province Strait from 13 to 16.5438+0. Huge waves of 4.0 to 5.5 meters appeared in the southern part of the East China Sea. 1 1, a big wave of 3.5 meters was observed at Chongwu Station in Fujian Province, and a large wave of 2.5 meters was observed at several ocean stations in eastern Guangdong Province, Fujian Province and southern Zhejiang Province.

Affected by this, 256 fishing boats in Fujian coastal waters lost contact, with death 1 person, mariculture12,680 hectares, breakwater damage 1.76 km and bank protection damage of 2. 18 km. The disaster caused direct economic losses of 336 million yuan.

2. "10 29" cold air wave

The cold air wave process affected most of China's sea areas from1October 29th to1October 5th in 65438. Huge waves ranging from 4.0 meters to 6.0 meters appeared off the coast of China, of which 4.0 meters were observed by the Yellow Sea buoy and 5.5 meters by the East China Sea buoy. The cold wave process caused 400 hectares of mariculture loss in Liaoning province, 3.35 kilometers of breakwater and revetment damage, and many coastal docks and offshore engineering facilities were damaged. The disaster caused direct economic losses of 75.5 million yuan.

See Table 6 for the process and losses of wave disasters in 2009.

[1] Waves with a wave height of more than 4 meters are called disastrous waves.

[2] The waves caused by tropical cyclones are called typhoon waves; Waves caused by extratropical cyclones are called cyclone waves; The fluctuation caused by cold air is called cold air wave.

Fourth, the sea ice disaster

In the winter of 2008/2009, the ice conditions in the Bohai Sea and the northern Yellow Sea were [1] weak all the year round. Except Laizhou Bay, the initial glacial period in other sea areas of Bohai Sea is 20 ~ 30 days later than normal, and the final glacial period is earlier 10 ~ 20 days. The ice age is more than 30 days shorter than normal, and the ice situation in the whole winter is roughly the same as that in previous years.

From late October to early February, 2009/kloc-0, 65,438 was the most severe ice situation this year, and the sea ice coverage area is shown in Figure 8. The largest floating ice range in Liaodong Bay appeared in early February, which was 65 nautical miles. The average ice thickness is 5 cm to 15 cm, and the maximum is 30 cm. The largest floating ice in Bohai Bay appeared in late June of 1, which was 18 nautical mile. Generally, the ice thickness is 5 cm to 10 cm, and the maximum is 20 cm. The maximum ice floe range in Laizhou Bay appears in the last ten days of 1, which is 32 nautical miles. Generally, the ice thickness is 5cm to10cm, and the maximum is15cm. The largest range of ice floes in the northern Yellow Sea appeared in early February, which was 20 nautical miles. Generally, the ice thickness is 5 cm to 10 cm, and the maximum is 30 cm.

Sea ice has affected and lost ports in Bohai Sea and northern Yellow Sea to varying degrees, with a direct economic loss of170,000 yuan. Among them, Panjin City, Liaoning Province 1 dock closure 120 days, resulting in direct economic losses of 5 million yuan; Seven docks along the coast of Hebei Province were frozen for more than 60 days, and the loss of aquaculture was 6.5438+million yuan. In Changyi City, Shandong Province, the wharf 1 was frozen and stranded, and the ship 1 1 was damaged, resulting in a direct economic loss of 2 million yuan.

[1] refers to the average ice condition from 1978 to 2008.

Verb (abbreviation for verb) tsunami disaster

There was no tsunami disaster in China in 2009. The State Oceanic Administration released the tsunami information of 29 submarine earthquakes that occurred in China and other sea areas of the world. These earthquakes (Figure 9) and tsunamis did not affect China, and no tsunami waves were detected by coastal tide stations.

Focal distribution map of China earthquake and tsunami in 2009.

Six, the red tide disaster

(A) the overall disaster situation

In 2009, there were 68 red tides in China's coastal areas, with an accumulated area of 14 1002 square kilometers, resulting in direct economic losses of 65 million yuan. Among them, the Bohai Sea has four times, with a cumulative area of 5,279 square kilometers; Yellow sea 13 times, with a cumulative area of 1878 square kilometers; 43 times in the East China Sea, with a cumulative area of 6,554 square kilometers; 8 times in the South China Sea, with a cumulative area of 39 1 km2.

In 2009, the red tide occurred frequently from April to August (figure 10), and the high-incidence area was the East China Sea (the frequency and cumulative area accounted for 63.2% and 46.5% of the whole sea area respectively). Large-scale red tides mainly occur in Bohai Bay and Zhejiang coastal waters. Toxic red tides * * * occur 1 1 time, accounting for 16.2% of the whole sea area. The main species that cause red tide are noctiluca scintillans, Skeletonema costatum, Heteroscella akashiwo and Karenina. Some red tides consist of two or more red tide organisms.

Figure/10 2009 Number of red tides in China offshore in 2009.

Compared with the average frequency and average area from 200 1 to 2008, the number of red tides in the whole sea area in 2009 was less, and the cumulative area changed little. The frequency of red tides in Bohai Sea and Yellow Sea decreased slightly, but the cumulative area increased greatly. The frequency and cumulative area of red tides in the East China Sea have decreased. The frequency and cumulative area of red tides in the South China Sea have not changed much.

Compared with 2008, the number of red tides in the whole sea area remained unchanged in 2009, and the cumulative area increased by 364 square kilometers. The occurrence of red tides in Bohai Sea and Yellow Sea increased four times, and the cumulative area increased by 5,549 square kilometers. The number of red tides in the East China Sea decreased by 4 times, and the cumulative area decreased by 55 16 square kilometers. The frequency of red tides in the South China Sea was the same as that in 2008, and the cumulative area increased by 33 1 km2.

(2) Major red tide processes

In 2009, there were 20 red tides with an area exceeding 100 square kilometers, with a cumulative area of 12940 square kilometers, accounting for 29.4% and 9 1.8% of the total red tides in the whole sea area respectively. Among them, the red tide with an area of 1000 square kilometers occurred three times, with a cumulative area of 7290 square kilometers.

1. Red tides in the waters near Bohai Bay

On May 3 1 day, a large-scale red tide occurred in the sea area near Bohai Bay, lasting for 14 days, with a maximum area of about 4,460 square kilometers. The water body in the red tide occurrence area is red and purple, and the dominant species of red tide is Heteroscella akashiwo, which is the most frequent occurrence this year.

2. Red tide in the waters near Rinan Island, Putian City, Fujian Province

On May 17, a red tide occurred in the waters near Rinan Island, Putian City, Fujian Province, lasting for 8 days, with an area of 10 square kilometer. The red tide is dominated by night algae, and the red tide waters are distributed in red stripes. The red tide disaster caused a loss of 60 million yuan in marine aquaculture.

3. Red tides at Longwangtou Beach and Liu Shui Wharf in Pingtan County, Fujian Province.

On May 23rd, a red tide occurred in Longwangtou Beach and Liu Shui Wharf in Pingtan County, Fujian Province, which lasted for 2 days and covered an area of 20 square kilometers. The red tide is dominated by night algae, and the water in the red tide area is distributed in dark red stripes. The red tide disaster caused a loss of 50 million yuan in marine aquaculture.

See Table 7 for the red tide process with an area of 100 km2 in 2009.

Red tide process in China 100 square kilometers in 2009.

Start and end times

sphere of influence

Maximum area

(square kilometers)

Dominant species of red tide

April 9(th)

Yangtze estuary waters

100

—

April 28(th)

Taizhou peripheral waters

700

Gymnodinium

Gymnodinium

2 May-7 May

Yushan Islands-Taizhou Islands Sea Area

1330

—

May 7-May 12

Sea area near Rizhao, Shandong Province

580

Noctiluca scientillans

Noctiluca scientillans

May 7-May 12

Wenzhou Cangnan Dayuwan Sea Area

200

Prorocentrum donghaiense

Prodinoflagellate

May 10

North Zhoushan sea area

360

—

65438 May 2006 to 65438 May 2008

East of Dongjiao Island in Taiwan Province Strait

200

Noctiluca scientillans

Noctiluca scientillans

May 65438 to May 30, 2009

Outside the Yangtze River Estuary and North Zhoushan

1500

—

May 26th to June 1

Sea area near Haiyang to Rushan, Shandong Province

550

Noctiluca scientillans

Noctiluca scientillans

May 26th to June 1

Sea area near the new opening in Changli County, Hebei Province

460

Noctiluca scientillans

Noctiluca scientillans

May 3 1 to June 13

Sea area near Bohai Bay

4460

Heterocurva akashiwo

Heterocurva akashiwo

June 4th.

North Zhoushan sea area

celebrity

—

June 1 1

Jiangsu Nantong offshore waters

350

—

June 65438 to June 22, 2007

East of Zhoushan Zhujiajian Island Island

3 10

Skeletonema costatum and Chaetoceros spiralis

Skeletonema costatum,

Chaetoceros curvata

June 65438 to June 22, 2007

The southern waters of Shanxi Province

230

Skeletonema costatum and Chaetoceros spiralis

Skeletonema costatum,

Chaetoceros curvata

July 65438 to July 23, 2008

East-West Island of Lianyungang City and Northeast Sea Area of Seawall

2 10

Karen Michaelis

Michelangelina

July 27(th)

Eastern waters of Zhoushan Island

300

—

August 1 to August 3rd

North of Tianjin Port Channel to Hangu Offshore Area

300

Skeletonema costatum

Skeletonema costatum

August 4-August 5

Eastern waters of Zhoushan Zhujiajian Island Island

120

Spindle algae

Keratosporium

65438+1October 27th to165438+1October 9th.

Sea area near Qi 'ao Island in Zhuhai City

280

Spirogyra polycephala, Gymnodinium rubrum and Skeletonema costatum.

Spinosad, Gymnodinium, Skeletonema costatum

Seven, Enteromorpha disaster

Sporadic floating Enteromorpha prolifera was first discovered in the sea east of Lusi, Jiangsu Province on March 24th, 2009, and was discovered in the sea east of Yancheng, Jiangsu Province on June 4th, 2009, with a distribution area of about 6,550 square kilometers and a coverage area of about 42 square kilometers. With the drift and growth of Enteromorpha prolifera, the distribution area of Enteromorpha prolifera reached the maximum in early July, about 58,000 square kilometers, and the actual coverage area was about 2 100 square kilometers, increasing by 132% and 223% respectively compared with 2008, which mainly affected the coastal waters in southern Shandong Province, as shown in Figure 1 1. After entering August, Enteromorpha prolifera in the Yellow Sea gradually decreased, and by the end of August, Enteromorpha prolifera in Shandong coastal area disappeared.

The outbreak of Enteromorpha prolifera in the Yellow Sea has a large area and a long duration, which has a serious impact on fisheries, aquaculture, marine environment, landscape and ecological services. The direct economic loss of Shandong Province is 646,543.8+0 billion yuan.

Eight. beach erosion

The areas with serious sandy coastal erosion are mainly Yingkou Bayuquan coastal area in Liaoning Province and Suizhong coastal area in Huludao, Qinhuangdao coastal area in Hebei Province, Longkou coastal area to Yantai coastal area in Shandong Province, east coast of Minjiang Estuary in Fujian Province and Putian coastal area in Hainan Province, Wenchang coastal area and Nandujiangkou coastal area. The areas with serious erosion of muddy coast are mainly in Lianyungang-Sheyang estuary in Jiangsu Province.

In 2009, the coastal erosion monitoring of key coastal sections showed that the coastal erosion in Suizhong, Liaoning Province was mainly in the coastline from Liugu Henan to Xinlitun, with an average erosion rate of 2.5 meters per year. The maximum coastal erosion width is near Nanjiangtun, and the annual coastal erosion amount is 5 meters. Table 8 shows the monitoring results of coastal erosion in other key coastal sections.

Table 8 Monitoring results of coastal erosion in key coastal sections

Provinces (autonomous regions and municipalities directly under the Central Government)

Key shore section

Average annual erosion

Speed (m/year)

Liaoning province

Shandong Province

Jiangsu Province

Shanghai

Hainan province

Yingkou Gaizhou Bayuquan

From Longkou to Yantai

Lianyungang to Sheyang

Chongming Dongtan Bank Section

Zhenhai Village, Haikou City

0.5

4.6

13.2

1 1.2

5.0

Coastal and offshore sand mining, unreasonable coastal engineering construction, river water conservancy, sand interception by hydropower projects, coastal groundwater exploitation and mangrove felling are important causes of coastal erosion disasters, and sea level rise further aggravates coastal erosion.

Figure 12 The primary sandy coast in Suizhong City, Liaoning Province was eroded and destroyed.

Nine, seawater intrusion and soil salinization

Compared with the monitoring results in 2008, the areas with increased seawater intrusion mainly include Jinzhou and Huludao in Liaoning Province, Qinhuangdao and Tangshan in Hebei Province, Binzhou in Shandong Province, Changle City in Fujian Province and some areas in Zhangpu County. Seawater intrusion is increasing in Dandong Donggang, Liaoning Province, Chucun Town, Weihai City, Shandong Province, the coastal area of Zhang Cun Town, Chaozhou City, Guangdong Province and Beihai City, Guangxi Zhuang Autonomous Region. Drinking water wells and agricultural irrigation wells in some residential areas of Quanzhou City, Fujian Province and Yangjiang City, Guangdong Province are affected by seawater intrusion.

The areas with serious soil salinization are mainly distributed in Liaoning, Hebei, Tianjin and Shandong coastal plains. Compared with the monitoring results in 2008, the salinization scope in Gaizhou, Yingkou, Liaoning, east and west sides of Xiaoling River in Jinzhou, Longgang District, Huludao, Lishuyuan Village, Tangshan, Hebei, Nanbao Town, Nanpaihe Town, Bohai New District, Cangzhou, Weifang, Shandong and Zhang Cun Town, Weihai showed an expanding trend.

Salt tide invasion

In 2009, both the Pearl River Delta and the Yangtze River estuary suffered from salt tides many times.

Since June+10, 65438, the Xijiang River and Beijiang River Delta in Guangdong Province have suffered four severe salt tides. During the period, the maximum chlorine content of Zhuhai Pinggang Pumping Station in Modaomen Waterway in the lower reaches of Xijiang River reached 3820mg/L, among which the chlorine content exceeded 250 mg/L for 8 consecutive days, which had a great impact on the water supply in Zhuhai, Zhongshan and Macau. Salt tide in Dongjiang Delta has affected Xintang Waterworks, the main stream of Dongjiang River, and Dongguan No.2 Waterworks, the tributary of Dongjiang River. Up to 65438+February 7th, the maximum chlorine content at the water intake point of Dongguan No.2 Water Plant reached 650 mg/L. ..

Salt tide invaded the intake of Shanghai Baosteel Reservoir 12 times. Salt tide invaded in winter and spring from the first half of the year/KLOC-0 to April, ***7 times, lasting 5.2 days on average; In the second half of the year, from June 10 to February 12, the salt tide invaded in autumn and winter for ***5 times, lasting for 5 days on average. Among them, the longest and most serious salt water intrusion occurred from February 12 to February 22, lasting 9.7 days, and the maximum chlorine content reached 1334 mg/L on February 17.

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