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9.1 Ecological Environment Monitoring of Wanzhou Model Zone
Runoff plots trial for the study and monitoring of ecological environment of Wanzhou model zone continued in 2004. The trial carried out comparison observation on soil water content and soil erosion under different modes of land use. Moreover, efforts were made to promote the application of ecological agricultural techniques such as compound farming of grain crops, cash crops and fruit trees on ridges in slope farmland and the establishment of biological fence on steep slopes. As a result, good economic and ecological benefits had obtained.
9.1.1 Trial of compound farming of grain crops, cash crops and fruit trees on ridges of slope cropland
The patterns of compound farming of grain crops, cash crops and fruit trees on ridges of slope farmland (Pattern I), compound farming of grain crops, cash crops and fruit trees on flat farmland (Pattern II) and the planting of grain and cash crops on flat farmland (Pattern III) have been operated for three years. The comparison trial findings showed that Pattern I enjoys the best effects in soil water retention with the highest soil water content, followed by Pattern II and Pattern III. The lapse rate of soil water content and the variation of soil water contents at different soil layers after rainfall was the highest in Pattern III, followed by Pattern II and Pattern I. Under the same land-use mode, the changing rate of soil water content is smaller in spring, autumn and winter as compared with that in summer. Compared with the previous year, soil water retention capability of Pattern I improved with some reduction of the lapse rate of soil water content. Soil water retention capability did not have much change in Pattern II, but had some rise in the pattern of flat cultivation of crops along the slope.
In comparison, Pattern I achieved the best results in reducing soil erosion and run-off with highest concentration of various nutrients in eroded soil. Pattern II had less good results while Pattern III the worst. If we compared with that of 2003, the level of various nutrients of the eroded soil from Pattern I rose to different extent. For example, the concentrations of organic matter, total nitrogen, total phosphorus, total potassium, quick-acting nitrogen, quick-acting phosphorus and quick-acting potassium rose by 9.98%, 11.46%, 10.98%, 5.37%, 8.20%, 22.58% and 13.91% respectively compared with that of 2003.
9.1.2 Trial of the pattern of steep slope with biological fence
Comparison trial was continued to observe the effect of steep slope cropland fenced with shaddock-king grass hedgerows (Fence Pattern) and the pattern of flat cultivation of pure grain crops along the slope (Pure Grain Crops Pattern). The findings indicated that both soil water content and the changing rate of the moisture in different soil layers of the 3-year-long Fence Pattern were higher than the Pure Grain Crops Pattern. The soil under the hedgerows enjoyed the highest soil water content with relatively small change rate (or variations) after rainfall. The water content of the soil up to the hedgerows and down to the hedgerows was similar and had relatively big variations after rainfall.Compared with the previous year, the post-rain lapse rate of soil water content of the Fence Pattern decreased while its water retention capability improved. However, there was no significant change in both the post-rain lapse rate of soil water content and water retention capability for the pattern of flat cultivation of pure grain crops along the slope.
Compared with Pure Grain Crops Pattern, Fence Pattern was more effective in preventing soil erosion and surface runoff with higher concentrations of various nutrients in eroded soil. The concentration of such items as organic matter, total nitrogen, total phosphorus, total potassium, quick-acting nitrogen, quick-acting phosphorus and quick-acting potassium were all higher than that of previous year, rising by 14.20%, 15.96%, 17.07%, 2.67%, 16.33%, 26.43% and 6.88% respectively.
9.2 Ecological Environment Monitoring of Zigui Model Zone
Zigui Ecological Environment Experimental Station continued the monitoring and study on soil erosion and soil fertility of arid slope cropland in Zigui area at the head of the Three Gorges Reservoir in 2004. It also further promoted the demonstration project of comprehensive technical trial of pollution-free navel oranges.
9.2.1 Soil and water erosion monitoring
The monitoring results on soil and water erosion of arid-slope orchard plot and forage grass-grain cropland plot under different water conservation measures showed that high natural biological fence like orchard and forage grass-grain crop fence could not only conserve water and soil, but also effectively reduce the loss of nitrogen in the runoff. Compared with intercrop pattern of wheat-peanut planting, high biological fence like orchard could reduce soil erosion modulus by 90.8% and reduce the loss of nitrogen by 81.7%. And a comparison between forage grass-grain crop fence and wheat-peanut pattern found that the former could reduce soil erosion modulus by 89.8%~91.2% and nitrogen loss by 47.7%¡«53.4%.
The coverage of vegetation may reduce soil erosion to some extent, but it was not the absolute factor. Different soil disturbance under different management measures would also impose evident impacts on soil erosion. Ploughing and low vegetation coupled with rainfall were the fundamental cause for heavy soil erosion.
9.2.2 Soil fertility monitoring
Straw mulching and white clover vegetation applied in orchard proved to be effective to enhance soil fertility. Compared with wheat-peanut intercrop pattern, the two techniques enabled the content of organic matter to increase by 44.7% and 26.3% respectively, total nitrogen by 24.0% and 26.0%, but no evident change in toal phosphorus and total potassium in the surface soil layer (0~20cm) of the orchard. There was no significant increase in nutrient contents under orchard-biological fence pattern. Compared with wheat-peanut farming pattern on arid slope cropland, the pattern of wheat-peanut-Chinese toon biological fence had increased content of organic matter, total nitrogen, total phosphorus and total potassium by 1.5%, 51.7%, 12.8% and 12.6% respectively. Alfalfa pattern and the ryegrass-amaranth pattern had a poor growth and unsatisfactory soil improving effect due to their poor resistance to drought.
9.2.3 Demonstration of comprehensive culture technique for pollution-free navel orange
The comprehensive culture technique for pollution-free navel orange was further promoted in 2004. Major technical measures of this technique included water-saving irrigation, the application of organic fertilizers, grass vegetation, hanging lamps, applying predator mites to control harmful mites and hanging bottles on tree crown.
A total of 1,000 mu (15mu= 1 hectare) of land applied water-saving irrigation technique, 530 mu for sprinkler irrigation, 100 mu for drip irrigation and 370 mu for low-micro sprinkler irrigation. The organic fertilizer demonstration projects applied a total of 500 tons of organic biological fertilizers. In grass vegetation demonstration projects, such techniques of planting and growing grasses on orchard were employed. Such grass species as bahiagrass, white clover and ageratum conyzoides were planted between lines in orchards. In the lamp hanging demonstration projects, 80 resonant frequency killing lamps were installed with one lamp per 30 mu of land, covering an effective area of 2,400 mu. In the mite control demonstration project, 14,400 bags of predator mites were distributed among the region.
9.3 Groundwater Table and Soil Gleization Monitoring
The monitoring on groundwater table from Xiaogang to Shimatou around the "four lakes"at the middle reaches and the observation on gleization indicators of soil at different gleization degree continued in 2004.
9.3.1 Groundwater table monitoring
The groundwater monitoring section consisted of 10 long-term observation boreholes in 5 groups. The distances from the 5 groups of borehole marked with the code of A, B, C, D and E to the Yangtze River bank was 1.5 km, 3.0 km, 5.0 km, 8.5 km and 13.0 km respectively. The depth of boreholes of confined water was about 35m while that for phreatic water observation was 5m~7m deep.
The average annual groundwater level of all observation boreholes ranged from 21.12 m to 22.33m in 2004 with fluctuations of 0.83m~2.50m within the year. The phreatic surface changed from 20.63m to 23.14m with maximum fluctuation margin of 2.51m. And the water table of confined groundwater varied from 20.73m to 23.49m with the maximum change margin of 2.76m. Be it confined or phreatic water, the highest groundwater table mostly occurred in August and the lowest in February. Compared with past few years, the annual average groundwater tables of both the confined and phreatic water had some decrease in general and the decline of phreatic water level was rather evident. The drop of groundwater level would impose certain influence on soil gleization.
Table 9-1 Water table of each observation borehole in 2004
Unit: m
|
Borehole |
Confined water table |
Phreatic surface |
|
A |
B |
C |
D |
E |
A |
B |
C |
D |
E |
|
Annual average |
22.27 |
21.45 |
21.86 |
21.45 |
21.9 |
22.04 |
22.33 |
22.15 |
21.96 |
21.89 |
|
Maximum |
23.49 |
22.3 |
22.85 |
22.02 |
22.36 |
23.13 |
23.14 |
22.8 |
22.59 |
22.48 |
|
Minimum |
21.04 |
20.73 |
20.99 |
20.73 |
21.53 |
20.63 |
21.46 |
21.41 |
21.4 |
21.54 |
|
Change margin |
2.45 |
1.57 |
1.86 |
1.29 |
0.83 |
2.5 |
1.68 |
1.39 |
1.19 |
0.94 |
Table 9-2 Annual average water table of each borehole during 2001-2004
|
Borehole |
Confined water table |
Phreatic surface |
|
Year |
A |
B |
C |
D |
E |
A |
B |
C |
D |
E |
|
2001 |
22.38 |
21.73 |
21.78 |
21.41 |
21.76 |
22.53 |
22.6 |
22.26 |
22.02 |
21.74 |
|
2002 |
22.53 |
21.76 |
21.93 |
21.45 |
21.9 |
22.45 |
22.64 |
22.33 |
22.17 |
21.88 |
|
2003 |
22.51 |
21.72 |
21.83 |
21.45 |
21.95 |
22.04 |
22.57 |
22.25 |
22 |
21.94 |
|
2004 |
22.27 |
21.45 |
21.86 |
21.45 |
21.9 |
22.04 |
22.33 |
22.15 |
21.96 |
21.89 |
9.3.2 Soil gleization indicators monitoring
Indicators of soil gleization at soil sections affected by different degrees of gleization were monitored continually in 2004 from the groundwater observation sections from Xiaogang Farm to Shimatou. The monitoring work was carried out once in winter and once in summer. Indicator parameters monitored included oxidation reduction potential, total amount of reduction materials, active reduction materials and ferrous iron, etc.
Monitoring results indicated that compared with the previous year, all gleization indicators were obviously lower, particularly in winter. In view of the overall soil sections, it was found that all the gleization indicators had evident seasonal variations. The amount of total reduction materials, the concentration of active reduction materials and ferrous iron were bigger in summer than that in winter and the order of content spacial distribution in soil sections from big to small was: surface layer > subsurface layer > subsoil layer. However, pH and Eh values showed a reserve order. In view of different layers of a soil section, seasonal change of indicators was big in surface layer and small in subsoil layer. The change margin of soil gleization indicators of different layers and sections was bigger in summer than in winter.
9.4 Special Monitoring on Terrestrial Plant Community
A special monitoring was undertaken in 2004 in order to accumulate vegetation baseline information during initial impoundment period of the Three Gorges Reservoir, analyze the status of plant communities and give objective assessment on the conditions of terrestrial eco-system of the reservoir area. The main activities of this special monitoring included data collection, identifying investigation samples and quadrat of plant community, collecting field samples and conducting site visits to the eastern and central parts of the reservoir area.
9.4.1 Identifying fixed monitoring sample plots
The investigation of plant communities of the reservoir area was carried out by identifying and setting up fixed monitoring sample plots and quadrats. Sample plots were selected according to different community types (biome), taking account of the representativeness of their geographical location, administrative jurisdiction and natural environment. In 2004, a total of 193 fixed sample plots with a total area of 4.18 ha were identified in 12 counties (cities) in the reservoir area and 377 quadrats were set up, collecting over 1,500 botanical samples and 193 soil samples. The sample plots could be divided into two groups by geographical location, 83 to the south of the Yangtze River and 110 to the north. When classified according to their altitude, 76 were in low altitude areas, 43 in middle altitude and 74 in high altitude.
9.4.2 Investigation on vegetation type
In 2004, 69 vegetation types were investigated including 41 forest types, 15 shrub types and 13 herbosa types.
¡ñ Forest
The distribution area of natural vegetation of the reservoir area, especially forests, has been narrow and small due to strong influence of long-term human activities, most of which were secondary forest. The zonal vegetation of evergreen broad-leaved forest only remained in a few areas. Forest vegetation concentrated in Shizhu County and Wulong County, which were to the south of the Yangtze River while natural forests (excluding Chinese red pine and cypress, etc.) to the north of the Yangtze River were mainly distributed in mountainous areas, such as Longmenhe Forest Farm of Xingshan County, Baiguo Forest Farm of Wuxi County and Dalaoling Forest Farm of Yichang, which were near Shennongjia forest zone.
The low altitude areas below 600 meters were mainly reclaimed farmlands and orchards with few forests due to relatively high density of population. Most forests were distributed in steep mountainous areas above 1,000 meters. Areas at middle altitudes of 600 ~ 1,000 meters were transitional belts where forest coverage gradually increased while farmland decreased from low to high altitudes.
¡ñ Shrubs and grasses
Most of shrubs and grasses in the reservoir area were degraded secondary ones. Vitex negundo, cotinus coggygria and coriaria intermedia were most common bush types covering the majority of the reservoir area and were distributed in a wide range of altitudes. The most common grass species were heteropogon, imperta cylindrica and arthraxon, etc., most of which were pioneer communities evolved on the degraded heathland.
9.5 Ecological Environment Monitoring of Estuary Area
In 2004, monitoring on river mouth eco-environment continued to focus on the monitoring on the change trends of water and salt concentration at land-sea interface and the comprehensive monitoring on biological and non-biological environment of river mouth waters.
9.5.1 Water and salt concentration trend
Three monitoring sections were established at the land-sea interface at the northern tributary estuary of the Yangtze River in 2004, which located at Yinyang Town, Daxing Town and Xinglongsha Seed Multiplication Farm of Qidong City, Jiangsu Province. The distance of the three sections to the northern tributary estuary was 4 km, 22 km and 35 km respectively. Three monitoring sites (from south to north) were placed at each section with their distance to the Yangtze River bank being 200 m, 500 m and 1,000 m respectively. Major monitoring items included soil conductivity, soil negative pressure, groundwater table and groundwater conductivity of the tributary estuary areas.
The water table of Yinyang section has risen by 15cm in spring and declined by about 10 cm in autumn and winter compared with the historical average of previous years. But the change of water table was smoother in comparison with that of past record. Soil water content was closely related to water table and varied with different seasons. Groundwater conductivity has gradually decreased since the power plant was established in 1997. However, the river water conductivity and groundwater conductivity both increased in 2004 compared with that of 2003 and the increasing margin was particularly obvious in autumn and winter.
The dynamic change of water table at Daxing section was in line with the change of water level of the Yangtze River. Compared with past record, the groundwater table did not change much in spring but had a sharp drop in autumn and winter. The groundwater conductivity has decreased by 0.8 mS/cm as compared with the historical average. The dynamic change of groundwater conductivity of full section was similar to that of the water of the Yangtze River. The farther the location of groundwater from the Yangtze River bank, the lower the groundwater conductivity was. This reflected evident influence of river mineralization on groundwater mineralization. The change pattern of the salt concentration of inland river water was similar to that of the Yangtze River. The average conductivity of 2004 has dropped somewhat compared with the historical average, but increased a little bit as compared with that of 2003. The soil conductivity also kept increasing in 2004.
The groundwater table of Xinglongsha section was a little higher in spring compared with that of the same period of the previous year, and also 10 cm higher than the historical average. Groundwater conductivity had some reduction compared with historical average since the establishment of the power plant, but was higher than the conductivity of 2003. The mineralization of inland river water was similar to that of the previous years. In 2004, the water conductivity of the Yangtze River was higher than that of inland river water. The conductivity of both the Yangtze River and inland river water had substantial fluctuations. However, the fluctuation of soil conductivity was relatively small.
Along the Yangtze River, the conductivity of the sections of the Yangtze River, inland rivers and groundwater varied as they were subject to different tidal influence. The monitoring results of Yinyang section (downstream) and Daxing section (upstream) showed that the change of the conductivity of the Yangtze River, inland river water, groundwater and soil presented similar pattern in line with the distance from the section to the estuary, that is, the nearer it was to the estuary, the higher the monitored value was. However, the changing margin of these monitored elements was different. The conductivity fluctuation of the Yangtze River was bigger than that of inland river water, and that of groundwater bigger than that of soil.
9.5.2 Non-biological environment of waters
¡ñ Hydrographic elements
The monitoring results of each season showed that the temperature of sea waters under investigation was from 7.96¡æ to 28.50¡æ with the maximum in August. In spring the average temperature of the Yangtze River estuary and its adjacent sea waters was 20.86¡æ on surface and 18.46¡æ in the bottom. The average water temperature did not change much in autumn compared with that of 2003. The minimum value of salinity was below 3 and the maximum being 34.49. The salinity showed the trend as being low at the estuary and adjacent sea waters, high in offshore waters; low on the surface and high at the bottom. However, there were some variations at different seasons and marine waters.
¡ñ Hydrochemical items
In 2004, the average values of the eight monitored indicators of the investigated marine waters were all bigger than that of the previous year. These 8 indicators included pH value, dissolved oxygen, COD, phosphate, silicate, nitrate, total nitrogen and total phosphorus. The average value of NH3-N was slightly lower than that of 2003 while the average concentration of nitrite did not have any change.
¡ñ Deposition items
The concentration of suspended matter in the investigated sea waters in the autumn of 2004 was between 1.7~320.6mg/L with the average of 17.8 mg/l, lower than that of the previous year. The concentration of suspended matter gradually decreased from the inland side of the Yangtze River estuary to the coastal side, and was higher at the bottom than in the surface layer. On the inland side of the estuary, the average concentration of suspended matter was 65.6 mg/l, forming a high-concentration area of suspended matter in the marine waters southeast to the mouth of the Yangtze River. But on the whole, whether on the inland side or coastal side, the concentration of suspended matter had an obvious reduction compared with that of 2003.
9.5.3 Biological environment of the waters
¡ñ Chlorophyll a
The concentration of chlorophyll a at the estuary of the Yangtze River in the spring, summer, autumn and winter of 2004 was 1.74?2.71 mg/L, 0.74?0.76 mg/L, 0.53?0.26mg/L and 0.44?0.18mg/L respectively.
¡ñ Phytoplankton
A total of 92 kinds of phytoplankton were collected and identified during the survey in 2004. Among them, 64 were diatom, 25 were dinophyta, 2 were chlorophyta and 1 was chrysophyta. Skeletonema costarum dominated all phytoplanktons and there were also a great deal of ditylum brightwellii and nitzschia pungens. Compared with 2001, there were 29 new species or subspecies of phytoplankton.
The amount of phytoplanktons in the investigated sea waters was 1.75¡Á104/m3 ¡« 1.11¡Á109/m3 with big regional difference and the average of 5.34¡Á107/m3.
¡ñ Zooplankton
A total of 123 kinds of zooplanktons were collected at the Yangtze River estuary in 2004. Maximum zooplankton density of the area was 725.3/m3 and the minimum 107.5/m3. The density of copepoda, jelly fish and arrow worms had some increase compared with that of the previous year.
¡ñ Benthos
Investigation and analysis identified 215 species or subspecies of benthos, including 112 species of hairy organisms, 54 species of mollusks, 27 species of crustaceans, 7 species of echinoderm and 15 other species. Hairy organisms dominated all benthos, followed by mollusks. There were relatively fewer species of crustacean and echinoderms. The overall density of benthos in the water was 19,543/m2 in maximum and 6,253/m2 in minimum. Among all the benthos, hairy organisms had highest density, reaching 12,000/m2 in May and 15,640/m2 in November. The density of mollusks ranked the second, which was over 1,000/m2.
Compared with the same period of previous years, the total species and total average biomass of benthos did not have any significant change in spring but showed some decline in autumn.
¡ñ Ichthyic plankton
Biological investigation at the Yangtze River estuary had obtained 734 samples of 44 species of ichthyic planktons in 2004. The dominant species were lion fish, lizard fish, taperail anchovy, engraulis japonicus and anchoviella commersonii.
¡ñ Fishery resources
The fishery resources investigation in 2004 identified 83 species of biological resources, including 52 fish species and 31 invertebrate species. The dominant fish species included setipinna taty, harpodon nehereus,tapertail anchovy, hairtail and Psenopsis anomala while the dominant species of invertebrate were crangon affinis, palaemon gravieri, palaemon carincauda, sanderia, jelly fish, charybdis bimaculata and portunus.
Compared with past years, both the species and amount of fishery resources have declined and only accounted for half of previous years' record in spring and two thirds of that in autumn. In spring the estuary and adjacent sea waters were filled with jelly fish, mostly sanderia of little economic value. The stock of economic fish species and invertebrates has dumped to a record low. In autumn this year, the dominant species underwent some change and the dominant fishery species in past years, i.e. cyanea capillata Linnaeus, did not appear.
9.6 Study on Endemic Fish Species
In 2004, study on special fish species was conducted to observe the early stage growth of such fish species as Procypris rabaudi, Sinilabeo rendahli and Ancherythroculter nigrocauda. Meanwhile, a series of experiments were conducted. The experiment and trial focused on the artificial propagation of Procypris rabaudi and Sinilabeo rendahli, the duplication of artificial propagation on Ancherythroculter nigrocauda and the continuous accumulation of the information about artificial propagation of other endemic fish species.
9.6.1 Study on early stage growth
On the second day when the fry of Procypris rabaudi was born, the swim bladder I appeared and inflated. It was found that melanin appeared in its eyes. The fry was 8.9 ¡À 0.4 mm long on the third day of its birth and 33.3¡À0.9 mm on its 56th day, with average daily growth of 0.45 mm. On the fourth day of its birth, the fry's intestine was developed and the fry began to take food. On the 27th day of its birth, the fin was fully developed and the fry reached to its juvenile stage.
The total length of Ancherythroculter nigrocauda fry was 4.04 ¡À 0.09 mm. It began taking food on the fourth day of its birth. The growth of the fry slowed down as the time for initial food serving was postponed. On the 30th day, the squama appeared on its body. As all the fins reached full growth with just abdominal creases remained, the fry grew into the advanced fry stage.
9.6.2 Experiment of artificial propagation
A total of 31 artificial propagation experiments were conducted on 12 endemic fish species through drug fecundation and artificial insemination in 2004. Drug fecundation was successful for such species as Procypris rabaudi, Sinilabeo rendahli, Ancherythroculter nigrocauda, Onychostoma sima, Spinibarbus sinensis, Leiocassis longirostris and Culter alburnus. And the fry of Procypris rabaudi, Sinilabeo rendahli, Ancherythroculter nigrocauda, Onychostoma sima and Spinibarbus sinensis were raised. The successful artificial propagation of Sinilabeo rendahli was the first time in China.
Seven artificial propagation experiments were carried out on Procypris rabaudi, four of which were successful. The total fecundation rate was not high and the total amount of fry was not many. Over 60,000 Procypris rabaudi fry were produced during the whole year and about 18,000 juvenile fishes were raised apart from those used for observation and study. All the three artificial propagation experiments on Sinilabeo rendahli were successful, obtaining over 1.08 million fry. Apart from those used for study and for sale, about 1,000 were raised to young fishes. Artificial propagation experiment on Ancherythroculter nigrocauda was repeated once, breeding 50,000 fry with the average fry fecundation rate of 33.33%.
Host organization:
Department of Reservoir Management, the General Office of the State Council Three Gorges Project Construction Committee
Chief compiling organization:
China National Environmental Monitoring Center
Compiling members:
Hubei Provincial Office for Assisting Three Gorges Construction
Hubei Provincial Statistics Bureau
Chongqing Municipal Statistics Bureau
Chongqing Municipal Environmental Monitoring Center
Geological Hazards Monitoring Center of Three Gorges Reservoir, Ministry of Land and Resources
Environmental Protection Center of the Ministry of Communications
Water Conservation Committee of the Yangtze River
Office of the Fishery Resources Management Committee of the Yangtze River
Agriculture Ecological and Environmental Protection Station of Hubei Province
Institute of the Aquatic Resources of the Yangtze River, the Ministry of Agriculture
Chinese Center for Disease Control and Prevention
Ecological and Environmental Monitoring Center of the State Forestry Administration
Institute of Hydrobiology, Chinese Academy of Sciences
Institute of Soil Science (Nanjing), Chinese Academy of Sciences
Institute of Oceanology, Chinese Academy of Sciences
Institute of Geodesy and Geophysics, Chinese Academy of Sciences
Institute of Mountain Hazards and Environment (Chengdu), Chinese Academy of Sciences
Institute of Botany, Chinese Academy of Sciences
National Climate Center
Institute of Earthquake Science, China Seismological Bureau
Department of Financial Planning, the General Office of the State
Council Three Gorges Project Construction Committee
China Three Gorges Project Corporation
Approval organization:
State Environmental Protection Administration
General Office of the State Council Three Gorges Project Construction Committee
Release organization:
State Environmental Protection Administration
Translation:
Department of International Cooperation, State Environmental Protection Administration
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