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5.1 Basic situation of Water Environmental Monitoring
In 2003, the monitoring of water environmental quality in the Three Gorges reservoir area included water quality monitoring in annual water season, monitoring of pollution belt along the riverbank in urban area and water quality monitoring in the second-stage water storage in the Three Gorges project. The assessment standard and test method were according with "the Water Quality Standard for Surface Water Environment"(GB3838 - 2002).
5.1.1 Annual water quality monitoring in the reservoir area
In 2003, 18 monitoring sections were set up in the Three Gorges reservoir area, including 15 mainstream sections and 3 subsidiary stream sections. 6 times of monitoring on water quality of rivers in urban areas in the reservoir area were conducted during three periods: dry season (February), normal season (May) and flood season (August). Three vertical lines, left, middle and right, were set up at each section to collect water sample from 0.5m deep under the surface for analysis.
5.1.2 Water quality monitoring in the second stage of water storage
On June 1, 2003, the Three Gorges reservoir started the second stage of water storage. In order to master the water quality status in the second stage of water storage in time, the State Environmental Protection Administration conducted synchronous monitoring on the water quality in the reservoir area day by day from May 25 to June 20. 6 monitoring sections were set up from Chongqing to the front of dam in Zigui, Hubei Province. There were 8 indicators monitored including dissolved oxygen, permanganate index, ammonia nitrogen, total phosphorus, volatile phenol, oil, lead and fecal Coliform bacteria.
5.1.3 Monitoring of pollution belt along the riverbank of urban area
In 2003, water quality monitoring along the river bank of the Yangtze River in the urban area of Fuling, Wanzhou and Zhongxian County during two periods: dry season (end of February) and normal season (end of May). 18 sections for sample collection were set up in the 29 km river course including 8 in Wanzhou urban area, 6 in Fuling urban area and 4 in Zhongxian urban area. 6 sample collection points were set up with different intervals in each section according to the actual situation of pollutant dispersion and water flow to collect surface water sample from 0.5m depth under the water surface for analysis. The water depth, flow speed and the distance to the bank of the sample collection points were also measured.
 Location of Water Quality Monitoring Sections of the River in the Three Gorges Reservoir Area
5.2 Water Quality in the Reservoir Area
5.2.1 Water quality in the reservoir area
The assessment of water quality in the reservoir area included 15 indicators: pH, dissolved oxygen, permanganate index, BOD5, ammonia nitrogen, oil, volatile phenol, total phosphorus, COD, cyanide, mercury, lead, cadmium, arsenic and hexad chromium. The results of the monitoring showed that in 2003, the overall water quality in the reservoir area was good and met or excelled the water quality standard for Grade III in all sections. There was no section where the water quality was under Grade I. Sections where the water quality met Grade II and Grade III accounted for 22.2% and 77.8% of the total area of all sections respectively.
Dry Season: The overall water quality in the Three Gorges reservoir area was generally good. There was no section where the water quality was under Grade I. Sections where the water quality met Grade II, Grade III and Grade IV accounted for 33.3%, 55.6% and 11.1% of the total monitored sections respectively. The exceeding standard factor was total phosphorus.
Normal Season: The overall water quality in the reservoir area was fairly good. There was no section where the water quality was under Grade I. Sections where the water quality met Grade II and Grade II accounted for 33.3% and 66.7% of the total monitored sections respectively.
Flood Season: The overall water quality in the reservoir area was fairly good. There was no section where the water quality was under Grade I. Sections where the water quality met Grade II and Grade II accounted for 33.3% and 66.7% of the total monitored sections respectively.
5.2.2 Annual variation
Compared with 2002, the water quality in the Three Gorges reservoir area had no obvious change in 2003, mostly meeting the water quality standard for Grade ¢ó.
Table 5-1 Assessment Result of Water Quality in the Three Gorges Reservoir Area in 2003
|
River nature |
City |
Section |
Dry |
Normal |
Flood |
Whole Year |
|
Season |
Season |
Season |
|
Main stream |
Yongchuan City |
Zhutuo |
¢ò |
¢ò |
¢ò |
¢ò |
|
Jiangjin City |
Huangqian |
¢ó |
¢ó |
¢ó |
¢ó |
|
Yuzhong District |
Wanglongmen |
¢ò |
¢ò |
¢ó |
¢ó |
|
Jiangbei District |
Cuntan |
¢ó |
¢ó |
¢ó |
¢ó |
|
Changshou District |
Huangcaoxia |
¢ò |
¢ó |
¢ó |
¢ò |
|
Fuling District |
Yazuishi |
¢ò |
¢ò |
¢ó |
¢ò |
|
Fuling District |
Qingxichang |
¢ò |
¢ó |
¢ó |
¢ó |
|
Fengdu County |
Mishiquan |
¢ó |
¢ó |
¢ó |
¢ó |
|
Zhongxian County |
Jiutiaohe |
¢ó |
¢ò |
¢ó |
¢ó |
|
Zhongxian County |
Lianerqi |
¢ó |
¢ó |
¢ó |
¢ó |
|
Wanzhou District |
Tongziyuan |
¢ô(×ÜÁ×0.03) |
¢ó |
¢ò |
¢ó |
|
Wanzhou District |
Shaiwangba |
¢ô(×ÜÁ×0.08) |
¢ó |
¢ò |
¢ó |
|
Yunyang County |
Xiayansi |
¢ó |
¢ó |
¢ó |
¢ó |
|
Fengjie County |
Baidicheng |
¢ó |
¢ó |
¢ó |
¢ó |
|
Wushan County |
Beishi |
¢ó |
¢ò |
¢ó |
¢ó |
|
Tributaries |
Yuzhong District |
Daxigou |
¢ó |
¢ó |
¢ò |
¢ó |
|
Fuling District |
Maliuzui |
¢ò |
¢ò |
¢ò |
¢ò |
|
Beibei District |
Beiwenquan |
¢ó |
¢ó |
¢ò |
¢ó |
Note: 1.The times exceeding the standard were calculated based on the standard for Grade III in the Water Quality Standard for Surface Water Environment (GB3838-2002)2.Fators and their exceeding the standard was put in the brackets.
Table 5-2 Comparison of the Annual Variation of Water Quality of River in Urban Areas in the Three Gorges Reservoir Area
|
Season |
Dry Season |
Normal Season |
Flood Season |
WholeYear |
¡¡ |
|
Year |
2002 |
2003 |
2002 |
2003 |
2002 |
2003 |
2002 |
2003 |
|
Total number of |
16 |
18 |
16 |
18 |
16 |
18 |
16 |
18 |
|
monitored sections |
|
Percentage of sections with Grade I and II water quality (%) |
68.8 |
33.3 |
0 |
33.3 |
25 |
33.3 |
43.8 |
22.2 |
|
Percentage of sections with Grade III water quality (%) |
25 |
55.6 |
87.5 |
66.7 |
56.2 |
66.7 |
50 |
77.8 |
|
Percentage of sections with water quality meeting or excelling Grade III (%) |
93.8 |
88.9 |
87.5 |
100 |
81.2 |
100 |
93.8 |
100 |
5.3 Water Quality in the Second Stage of Water Storage
The results of monitoring conducted from May 25 to June 20, 2003 showed that water quality in the reservoir area had no obvious change. The whole water quality mostly belonged to Grade III. The monitored value of volatile phenol, oil and lead met the requirement for Grade I water quality; dissolved oxygen, permanganate index and ammonia nitrogen met the requirement for Grade II water quality and total phosphorus basically met the requirement for Grade III water quality. With consideration of the index of fecal Coliform bacteria, the water quality belonged to Grade IV or sub-V as a whole.
Figure 5-1 Trend of Daily Change of Comprehensive Pollution Index
Figure 5-2 Trend of Daily Change of Permanganate Index Density
Figure 5-3 Trend of Daily Change of Ammonia Nitrogen Density
Figure 5-4 Trend of Daily Change of Total Phosphorus Density
Figure 5-5 Trend of Daily Change of Dissolved Oxygen Density
Figure 5-6 Trend of Daily Change of Fecal Coliform Bacteria Density
5.4 Pollution Belt of Urban Area Along the Riverbank
The factors of monitoring on the pollution belt of urban area along the riverbank were permanganate index, total nitrogen and total phosphorus. The results of monitoring showed that there were obvious riverbank pollution belts in urban areas of Wanzhou County and Zhongxian County. The riverbank pollution belts in Fuling urban area were relatively narrow.
¡ñ Dry Season
The pollution belt with pollution exceeding the baseline level in Wanzhou urban area was about 12,600m long (permanganate index) and 110m wide, accounting for 70.4% of the total length of monitored sections and 25% of the average width of the river surface. The pollution belt with pollution exceeding the standard was about 300m long (permanganate index),and 5m wide, accounting for 1.7% of the total length of the monitored section and 2% of the average surface width of the river, mainly spreading around the sewage outlets of big cities with a distance about 10m away from the outlets.
The pollution belt with pollution exceeding the baseline level in Zhongxian urban area was 1,200m long ((permanganate index) and 40m wide, accounting for 25.5% of the total length of the monitored sections and 8.6% of the average surface width of the river. There was basically no pollution belt exceeding standard.
The pollution belt with pollution exceeding the baseline level in Fuling urban area was about 4,500m long (total phosphorus) and 120m wide, accounting for 75% of the total length of the monitored sections and 30.2% of the average surface width of the river. There was no pollution belt exceeding standard.
¡ñ Normal Season
The pollution belt with pollution exceeding the baseline level in Wanzhou urban area was about 14,100m long (total phosphorus) and 110m wide, accounting for 78.8% of the total length of the monitored sections and 17.1% of the average surface width of the river. The pollution belt exceeding standard was about 900m (total phosphorus) and 15m wide, accounting for 5.0% of the total length of the monitored sections in the urban area and 2.3% of the average surface width of the river.
The pollution belt with pollution exceeding the baseline level in Zhongxian urban area was about 3,950m long (permanganate index) and 105m wide, accounting for 84.0% of the total length of the monitored sections and 16.8% of the average surface width of the river. The pollution belt exceeding standard was about 2,990m (total phosphorus) and 80m wide, accounting for 63.6% of the total length of the monitored sections in the urban area and 12.8% of the average surface width of the river.
The pollution belt with pollution exceeding the baseline level in Fuling urban area was about 2,900m long (total phosphorus) and 20m wide, accounting for 48.3% of the total length of the monitored sections and 4.0% of the average surface width of the river. The pollution belt exceeding standard was about 2,900m (total phosphorus) and 20m wide, accounting for 48.3% of the total length of the monitored sections in the urban area and 4.0% of the average surface width of the river.
Table 5-3 Scope of Pollution Belts of Urban Areas of Wanzhou, Zhongxian and Fuling Along the Riverbanks
|
River section |
Number of large scale discharge outlets |
Season |
Pollution |
Pollution belt exceeding the baseline level 5% over density of the inflow background |
Pollution belt exceeding standard over Grade III |
|
indicator |
Length (m) |
Width (m) |
Area (m2) |
Length (m) |
Width (m) |
Area (m2) |
|
Wanzhou section |
9 |
Normal |
Permanganate index |
12300 |
100 |
1230000 |
300 |
10 |
3000 |
|
Total nitrogen |
7600 |
70 |
532000 |
/ |
/ |
¡¡ |
|
Total phosphorus |
14100 |
110 |
1551000 |
900 |
15 |
13500 |
|
Dry |
Permanganate index |
12600 |
110 |
1134000 |
300 |
5 |
1500 |
|
Total nitrogen |
1200 |
45 |
54000 |
/ |
/ |
/ |
|
Total phosphorus |
7200 |
45 |
324000 |
250 |
10 |
2500 |
|
Zhongxian section |
3 |
Normal |
Permanganate index |
3950 |
105 |
414750 |
150 |
5 |
750 |
|
Total nitrogen |
3950 |
80 |
316000 |
/ |
/ |
/ |
|
Total phosphorus |
2990 |
80 |
239200 |
2990 |
80 |
239200 |
|
Dry |
Permanganate index |
1200 |
40 |
48000 |
/ |
/ |
/ |
|
Total nitrogen |
/ |
/ |
/ |
/ |
/ |
/ |
|
Total phosphorus |
/ |
/ |
/ |
/ |
/ |
/ |
|
Fuling section |
6 |
Normal |
Permanganate index |
/ |
/ |
/ |
/ |
/ |
/ |
|
Total nitrogen |
/ |
/ |
/ |
/ |
/ |
/ |
|
Total phosphorus |
2900 |
20 |
58000 |
2900 |
20 |
58000 |
|
Dry |
Permanganate index |
/ |
/ |
/ |
/ |
/ |
/ |
|
Total nitrogen |
1600 |
45 |
72000 |
/ |
/ |
/ |
|
Total phosphorus |
4500 |
120 |
540000 |
/ |
/ |
/ |
5.5 Comparison Analysis between Clear Water and Muddy Water
In 2003, the analysis results of the comparison between clear water samples and muddy water sample indicated that the contents of seven measured indicators (permanganate index, total phosphorus, mercury, As, lead, copper and cadmium if found) in muddy water samples were obviously higher than those in clear water samples, in which the difference of total phosphorous, permanganate index, copper and lead etc. was even more outstanding. And the differences between clear water samples and muddy water samples in the main stream of the Yangtze River were bigger than that in the tributaries. The concentration of monitored indicators in muddy water samples differed obviously with the change of the water period, having some relations with the existing of water seasons. However, the content in clear water sample was rather low and stable without obvious relation with water seasons.
Figure 5-7 Variation Trend of Annual Average Value of Permanganate Index along the Course in Mainstream of the Yangtze River in 2003
Figure 5-8 Variation Trend of Annual Average Value of Lead along the Course in Mainstream of the Yangtze River in 2003
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