Abstract:A scientific expedition on the Dongting Lake area in the middle Yangtze reaches was carried out shortly after heavy flooding of the Yangtze River in 1998.Based on the investigations and long-term studies concerning Dongting Lake, the authors point out that the interrelation between Dongting Lake and the Yangtze River is becoming more worsened during the past decades, resulting more frequent heavy flooding in the area.Furthermore, solutions to flood control and post-flood reconstruction for the flood-stricken areas are put forward, i.e., (1) techniques for the restoration of the reclaimed land in lakeside areas of Dongting Lake;(2) realignment of agricultural modes in the areas of the low-lying paddy fields which should be restored to the former state and reconstructed villages for cultivation purposes;(3) management as to make the most of the built water conservancy works;and (4) establishment of harmonious relationship between the lake and the river, etc.

Abstract:By using the hydrological and topographical data collected from hydrological stations around Dongting Lake, the amount of sediment deposition and erosion from the lake(1956-1995) is analyzed with sediment budget method and topographical method. The results demonstrate that the inflow from the Lishi River, Yuanjiang River, Xiangjiang River and Zishui River contributes 57.8% of the total water into Dongting Lake, while the runoff from the Yangtze River through 4 intakes and channels which connect the Yangtze River and the lake occupies 33.6%.Among the sediment transported into the lake, 79.5% is from the Yangtze River, 18.2% from the four tributaries and only 2.3% from the local area.Up to 74% of the sediment into the lake is deposited in the lake, with the rest carried out of the lake to the Yangtze River. The runoff flowing from the Yangtze River into the lake has been reducing because of the siltation of the lake. Hence the siltation rate and the flow returning into the Yangtze River decrease. The total amount of sediment deposition in the lakes in the past 40 years (1956-1995) was calculated at 4.93 billion cubic meters that made the lake silled up by 0.63-0.74 m. The rate of siltation is estimated at 0.018 m/a¹ with the sediment budget method and 0.016 m/a¹with the topographical method. Sedimentation in the period 1983-1995 led eastern part of Dongting lake shrank by 1.5%, southern part of Dongting Lake by 2.5%, Muping Lake by 5.4% and Qili Lake by 22.5%.In the past 40 years, the East and West branches of the Songzi River, the lower reaches of the Zishui River, the Caowei River, the south and north outlets of Dongting lake have exhibited a bed degradation by 1.03m, 0.5m, 0.26m, 0.67m, 0.15m and 0, 52m respectively, whereas the rest have silted up. In the main outlet of the lake, Chenglingji Station, erosion has been observed since 1988.The impoundment of the Three Gorges Reservoir will probably reduce the inflow of water and sediment to lake and the rate of siltation of the lake will slow down.

Abstract:The Tibetan Plateau plays a major role on modern atmospheric circulation of Northern Hemisphere, especially with respect to the Tropical Easterly Jet and monsoon circulation.Understanding the past climate in the plateau, especially during the late Pleistocene when the Tibetan Plateau uplifting accelerated, will be very important.A 310m core(RM) (33°57'N, 102°21'E) collected from the central part of Zoige Basin, east Tibetan Plateau was analyzed.The upper 31m provide a continuous palaeoclimate information in the past 140ka, which is reconstructed on the basis of stable isotope analyses (δ^l8O and δ¹³ of authigenic carbonate), content of carbonate, organic matter and pollen, etc.The results reveal significant changes of palaeoenvironmental condition, induced by climate changes and/or local hydrological factors.Five stages are identified.Stage 5(140-82kaBP) equivalent to Last Interglaciation was warm and wet.The primary productivity was high due to the optimum associaton of heat and moisture.5 substages (5a-5e) can be divided, moreover, 5e can be further divided into 5 subordinate substages (5e₁-5e₅).In the record, 5e is the warmest substage among them, while 5a is the optimum, and 5c is a weakly warm period.A series of cooling events have been recorded since stage 4 (82-l0kaBP).i.e.66, 51.5, 33, 28, 21 kaBP, equivalent to H6, H5, H4, H3, H2 event reported in deep-sea sediment.Comparison study has been done for the RM core record with the other records adjacent and in the world.The result also shows that the stage 3 was a conspiciouvs period, when the climate was very optimum.The basin Was cut off by the Yellow River ca 30kaBP, correspondingly the lacustrine deposits were replaced by fluvial and swamp deposits.

Abstract:Statistical frequencies of plentiful and scanty runoff of different time series, including annual runoff, runoff of flood period, dry and irrigation seasons, in Hongze Lake, Luoma Lake and Nansihu Lake were analyzed on the basis of historical runoff data.For all of these time series' estimated encountering frequencies of high-flow or low-(low in both Hongze Lake versus Luoma Lake and Hongze Lake versus Nansihu Lake were presented in this paper.Finally, statistical analysis of high-flow year group or low-flow year group and encounitering frequencies of annual and flood season runoff were studied.Some ideas of optimum development and comprehensive utilization of water resources in the Huaihe and Changjiang river basins were suggested for the East Route Project of South to North Water Transfer in China.

Abstract:According to the basic theory of water flow motion and the solution of Canadian Hydraulic Model, a hydraulic model applied to the characteristics of Taihu Basin network is established.By using the model to make hydraulic calculation in the network of the Wangyu River and ils branch rivers, the results indicate that the solution of the model is effective and the calculation accuracy is higher.

Abstract:A preliminary study on the advance and retreat of Qingtu Lake, Hexi Corridor and the sedimentary climatic records of Zhiyun Village profile has been made through comprehensive analysis.The study shows that the modes characteristics of climatic change in Eastern Hexi Corridor was provided with the corresponding relationship of warm-moist and cold-dry during the scale longer than hundreds of years.As a result of periodicity of climatic change and human activities, Qingtu Lake cycle has undergone a cycle since 600aBP with four lake-retreat and three lake-advance stages.In brief, the evolution of lakes in Eastern Hexi Corridor is characterized by sedimentary continuity, faster sedimentary rate and higher resolution, which not only can indicate the paleoenvironmental and climatic change in Holocene, but also can reflect the intensity of Eastern Asia monsoon.

Abstract:The historical changes of river channel (river floods) in the lower reaches of the Yellow River has been holly debated by the historians in China. In Nansihu Lake area, the sedimental environment has undergone great change, since the evolutionary history of the lake was strongly af fee led by floods of yellow River in historical times. High-resolution lacustrine sediments, reflecting the history of lake evolution, could be used Lo decipher the changes of river channel (river floods) in tne Lower Reaches of the Yellow River. Two sedimentary cores (DS₁ and DS₂) are taken by Livingstone in Dushan Lake, one of the sub-lakes of Nansihu Lake, 1996.The analysis of environmental indexes including pigments, TOC, TN and magnetic susceptibility, frequency dependent susceptibility, of lake sediments in the cores of DS is synthesized to indicate the environment changes in Nansihu Lake in the past 3000 years. About 2400aBP a clear environmental change occurred in the catchment of Nansihu Lake. From BC400s to ADI 70's and AD1200s-1870s are two main floods periods on the lower reaches of the Yellow River. Before 2400aBP the lake was not formed in the area which may be a depression in the edge of fluvial fan of the Sihe River and the Chenghe River. After 2400aBP the lake came into being and was enlarged due to the alluvial fan emerging from the overflow of the Yellow River, especially in BC400-AD170 and AD1200-1870.The link-up of the Grand Canal and the requisition for canal transportation from Lo AD1870 accelerated the lake expansion. From 1872, Nanyang Lake, Dushan Lake and Weishan Lake were united into one large lake-Nansihu Lake.

Abstract:This paper, based on the historical literature and field observations, outlines the formation and evolution of Hongze Lake and the Huaihe River mouth along the lake.Hongze Lake was the result and component part of the engineering of regulating the Yellow River and protecting the Grand Canal.The present Hongze Lake mainly formed at the end of the 17th century, when Jin Fu harnessed the Yellow River and the Grand Canal by lifting the water level of the Huaihe river.After the lake formed, its level began lo rise continually at an average rate of about 4,0cm.a 1 for more than 100 years. At the same time, the lake level changed with an annual range of 4.lm, which resulted in strong backward flow in the upstream, whose uplimit moved backward gradually. Accompanying the lake-level rising and lake-volume increasing, the lake current changed evidently, especially the Hongze Lake influent-effluent current became weaker and weaker from the 18th century. Although there were absolute proofs about the sub-delta and mouth sand bar in the 18th century, the present Huaihe River delta along Hongze Lake was formed since the 1850s AD under the stable lake level and current. In 1128-1851 AD, the lower Yellow River captured the Huaihe River and a great quantity of sand was accumulated in the middle Huaihe drainage, some of which was carried into the Huaihe River channel afterwards, and became the Huaihe delta, s material base. The river counter-S-shaped valley from Fushan down to the lake has contributed to the river current wearing and sand accumulating. The evolutional model of the estuary may be summarized as follows:(1) formation of shoals;(2) fluvialization of the lake; and (3) anastomosing of the channel.

Abstract:The aromatic hydrocarbon fraction of the surface sediment in the west and east part of Taihu Lake was analyzed by GC-MS.As a result, a series of long chain falty acid methyl esters was first found. Distribution of the carbon number of fatty acid methyl esters in the samples was from C₁₄ to C₃₄ maximizing at C₁₆ with a strong even to odd carbon preference.Their mass spectrum characteristics are that base peaks were M/Z 74, 87 and characteristic ions were M/Z 143, 199, M⁺, M-43⁺.These ion existence was confirmed by fragmenting analyses of fatty acid methy esters.The origin of the long chain fatty acid methy esters in the sediment of Taihu Lake was also studied, which may be related to biochemical process. The result showed that the long chain fatly acid methyl esters was probably an important biological marker to study the acidity of the lake sediment.

Abstract:The layer system of 48 targets was studied by using R-cluster analysis methods with fishery resource data (investigated from 1980 to 1992) of 55 reservoirs of 20 provinces in China. After comparing with the results of the two analysis methods, the target layer system for the fishery trophic classification of reservoirs in China was established. The 48 targets could be divided into 3 layers. The first layer includes 6 sub-levels: geography level (latitude-LN, illumination hours-IH), climatology level (annual no frost days-NFD, annual mean air temperature-AT, annual rainfall-RF), water depth level (maximum depth-MAXD, mean depth-MD), area and volume level (fishery area-FA, total storage capacity-TSC, profit storage capacity-PSC, dead storage capacity-DSC), soil level (catchment area-CA, draw-down area-DDA, DDA to FA index-DFI) and hydrology level (ratio of water exchange-RWE, CA to FA index-CFI, CA to TSC index-CCI).The second layer includes 5 sub-levels: major ions level, electrical conductivity-EC, total alkalinity-TA, total hardness-TH, value of pH-PH, TA to TH index-AHI), phosphorus level (phosphate phosphorus-P0_4-P, total phosphorus-TP), organic matter level (chemical oxygen demand-COD), dissolved gas level (dissolved oxygen-DO) and nitrogen level (ammonium nitrogen-NH_4-N, nitrite nitrogen-N0₂-N, nitrogen level nitrogen-N3, total nitrogen-TN).The third layer includes 4 sub-levels: phytoplankton level (density-DP, biomass-BP), zooplankton level (density-DZ, biomass-BZ), primary productivity level (phytoplankton primary productivity-PP), fish growth level (body length-SL and weight-SW and fatness-SFAT of two years silver carp, body length-BL and weight-BW and fatness-BFAT of two years bighead carp).

Abstract:The recovery of submerged macrophyte community is important to the purification of water quality and the restoration of beautiful landscape, and also to the sustentation of the lake fishery with high quality and high economic benefit because the fishery species with high market-price, such as Chinese mitten crab Eriocheir sinensis H. Milne-Edwards and mandarin fish Sini-perca chuatsi (Basilewsky), do not grow well without the densely submerged macrophyte community. By catching the herbivorous fishes (grass carp Ctenopharyngodon idellus, MegaLobrama amblycephala Yih, Cyprinidae) and the omnivorous fishes (common carp Cyprinus carpio L., crucian carp Carassius auratus L.) which are harmful to the submerged macrophyte growth, and transplanting the aquatic plants (Vallisneria natans, Potamogeton macckianus, MyriophylIum spicatum, Ceratophy Lurn demersum ) on the calm days in early spring when the water depth was 0.1-1.0 m, the submerged macrophyte community was recovered in Xiao-si-hai Lake (area is 133.3 ha) near to the middle reach of Yangtze River, China in 1995.Because of the recovery of submerged macrophyte community, the traditional fishery type which applying fertilizer to culture the plankton feeder (silver carp HypophthaLmichthys molitrix and bighead Aristichthys nobilis ) with low market price was given up, and began with a new fishery by stocking the crab and the mandarin fish to gain a great benefit in Xiaosihai Lake. The biomass, cover rate of submerged macrophyte is 2730g/m², 100%, respectively, in autumn in 1997, and the crab production is 4739.5kg in 1997.

Abstract:Erhai Lake is located in the west of Yunnan Province. It plays an important role in the Dali regional economic development. However, with the development of economy and increase of population in the region, the impacts of human activity on ecological environment of Erhai Lake have been strengthened. Based on the investigations on Erhai Lake from 1996 to 1997 and data of the past 40 years' research, this paper gives a detailed analysis on the succession of its aquatic communities. From 1957 to 1997, the density and biomass of phytoplankton increased nearly 10 times and this change was more intensive in the last 15 years. The dominant species have also changed greatly. The non-pollution resistant species such as Ceratium hanclelli Skuja, Psephone-ma aenigmaticum Skuja, Lyngbya Limnetica Lemm. have disappeared, while the species which can indicate eutrophication such as Anabaena spiroides Klebahn and Microcystis fios-equae (Wit-tr.) Kirch increased. Because of the transformation of “Four Domestic Fishes” and ice fish, the density and biomass of zooplankton have been decreasing.However, organic pollution resulted in the rise of density and biomass of limnitic oligochaeta and chironomid larvae. The density of zoobenthos has increased nearly 8 times. There are two apparent variation periods of aquatic vegetation. From 1957 to 1985, distribution of aquatic vegetation tended to expand. From 1985 to 1997, it tended to reduce because of unreasonable utilization. With the transformation of extra fishes, rapid decrease of water level, over capture of fish resources etc., the fish community of Erhai Lake has changed greatly. In the 1950s and 1960s, the fish community was dominated by aboriginal fishes. In the 1970s, the fish Ctenogobius cliffordpopei was dominant. In the 1980s, the dominated fish turned to Carassium auratus.In the 1990s, the ice fish and common carp become main economic fish of Erhai Lake.fishes tend to die out. The fish of Schizothorax taliensis has disappeared.

Abstract:In water ecosystems, enzymes play a key role in the processes of nutrient cycling and energy transformation. The origin, characteristics and ecological significance of the phosphatases in lakes, as an example, are reviewed in this paper. The enzymes, extracellular and dissolved, are mainly from bacteria, phytoplankton and zooplankton. They show stability and suitability towards the variations in pH value, temperature and other physical and chemical factors. Planktons seem to compensate for their phosphorus deficiency not only by an increase in enzyme production but also by an improved ability to use low substrate concentrations, which implies the potential significance of enzymes in environmental monitoring. Some ecological relationships might be explained from the points of view of enzymatic reactions. In short, the special and integrated functions of the enzyme in natural waters, in terms of nutrient supplying, nutrient status indicating and cycle mediating, have made it an essential part of the ecological enzymology.

Abstract:The content of nutrients which are composed of protein, Amino acid and fatty acid etc of Artemia (including assess the quality of nutrients and brine brine shrimp eggs) is the main criterion to Artemia, because the food value of animal of prey depends on the constituent and content of amino acid and fatty acid.The nutrient of the Artemia in Lagkor Co (Lake) of Tibet is of high value and a succession of samples taken by R & D Centre of Saline Lake and Epi-thermal Deposits (CAGS) were monitored in 1996 and 1997.The protein content of adult brine shrimp is nearly 20%, and that of nauplius and decapsulated brine shrimp eggs about 55% and 50% respectively. The raw fat content of adult brine shrimp is 30% and that of both nauplius and decapsulated brine shrimp eggs is about 15%. The total amount of amino acid of adult brine shrimp is 18% and that of nanplius and decapsulated brine shrimp eggs about 50% and 44% respectively. Among fatty acids the unsaturated fatty acid of adult brine shrimp is up to 83% in samples of 1997 and that of nauplius and decapsulated brine shrimp eggs about 91% and 87% respectively.For three unsaturated fatty acids, the content of HUFA(20 :3, 20 :4, 20 :5) of adult brine shrimp is nearly 8%, and that of both nauplius and decapsulated brine shrimp eggs exceeds 20%.For three necessary fatty acids, the content of EFA (18 :2, 18 :3, 20 :5) of adult brine shrimp is 16% and that of nauplius and decapsulated eggs is 21% and 26% respectively. The contents of EPA (20:5) of both nauplius and decapsulated eggs are above 18%. The content of EPA of Artemia in Lagkor Co is higher than that of Artemia in salt lakes of Xinjiang, Qinghai, Inner Mongonia, Shanxi, Hebei and that of Artemia in salterns of Tianjin and Hainan.The un-satulated fatty acid content of decapsulated brine shrimp egg in Lagkor Co is higher than that in other lakes at home and abroad.