Abstract:This hydrological system model for Taihu Lake Drainage Basin consists of five submodels, namely: model for network channels and lakes, model for boundary conditions; model for rainfall and runoff;model for hydraulic projects and their management;model for unsteady flow in network channels. The model was calibrated and tested comprehensively using the observed data in 1984 and 1985. The results are consistent with those observed. The model has been applied for studying flood, drought and management of Taihu Lake Drainage Basin. As an example of applying,the influence of land reclamation from lake on flood damage.the flood damage reduction after all projects completed and the choice of design flood year were introduced briefly in this paper.

Abstract:The heavy storm rain from May 21 to July 13,1991 caused huge torrents and hit this area. About 3309km² in Taihu Plain were submerged by the flood water with total economic losses of US $ 2×10⁹.According to the investigation and statistics it is showed that about 45.0% of the area was below 4.5m and 52.2% of the area below 3.5m,but the water stage during the flood time reached 4.79m,so that about 62.5% of the area below 4.5m was inundated by the flood water. About 95% of the flooded area belongs to the paddy field and vegetable land. About 4 million people were affected by the calamities.On the basis of distribution of the flooded area,it can be divided into five catastrophic regions:the western part of the Plain affected by the waterlogging;the sorrounding area of Taihu Lake hit by high-level of flood water;the east plain flooded regions as a result of blockage of the drainage river,and urban areas such as Suzhou,Wuxi and Changzhou and their suburbs due to the development of the urbanization.The huge rainfall in Taihu Plain reached 899mm with its frequency years of one time in 100-200 years, excessing its whole capacity. So the lake level rose to the historical height. Human activities,in other hand,are playing an important role in aggravating the seriousness of disasters. (1) The storage and regulation function in lakes and rivers were decreased in past fourty years as a result of siltation and reclamation. (2) The drainage channels were blocked up by siltation,for example 70 streams among 84 streams of outlets in Taihu Lake were blocked up. (3) The area protected by embankments surrounding the low-lying paddy fields has been increased and led to the loss of 633km² of drainage and storage area. (4) In the urbanized areas the drainage systems were unsuitable to the prevention of flood disasters.The countermeasures include the rational arrangement of reclamation and storage, regulation of lakes and rivers, drawing up a plan of urban and regional development coordinating with flood prevention, enhancing the nonstructural programms such as establishing a monitoring system,disaster data base and flood insurance.

Abstract:The climatic tendency of warming and drying since the beginning of this century has been shown distinctly in the mid-latitude zone of the North Hemisphere. It is of a series of impacts on the water resources system.especially in the arid or semi-arid regions. On the basis of this fact,the inland-lake changes in response to the climatic fluctuation are investigated. The comprehensive study shows that the general trend of the inland lake may be shrunk under warm and dry conditions. Further research of the impact of the changes in precipitation and temperature on the lake has been carried out,showing that the rise of temperature may cause an increase of the evaporation and runoff supplied by melting glacier,and that a decrease of precipitation may lead to reduction of the runoff and shrinkage of the lake area. Qinghai Lake is a typieal one which represents the lake evolution dominated by precipitation as well as Lake Issuk-kul dominated by temperature.

Abstract:Mineral magnetic measurement can contribute to lake sediment studies in a wide variety of ways,ranging from analysis of sediment sources to understanding of the response of lake sediments to climate change.The magnetic susceptibility (X) and the frequency dependent susceptibility (X_fd) curves of two short sediment cores from Qinghai Lake (QL₅) and Daihai Lake (DH₃₂). spanning respectively the last 500 and 300 years,have been made. It is interesting that the variations in X_fd(%) approximately coincide with those of geochemical and grain size analysis data. Additionally,due to the variation of magnetic mineral content >type and magnetic grain size controlled mainly by the processes of weathering, pedogenesis,erosion and so on,the curves (especially X_fd (%) curves) have all shown considerable regular alternations of wave peaks and troughs, implying climatic fluctuations in different time scales during historical period in the two areas. These results indicate that the magnetic parameters of lake sediments,especially their frequency dependent susceptibility are sensitive to paleoclimatic fluctuation and can provide us important information about climate change.

Abstract:Based on the Neolithic Culture data in Taihu Lake area,including the distribution and number of culture sites.production styles and the character of culture et al.,a research is made on the impact of environmental changes in Holocene Megathermal (8-3 ka B. P. ) on the development of the Neolithic Culture in this region. The results show that the warm, wet and stable climate in Holocene Megathermal was favourable to the living of ancient people in Nelithic Ages,as well as to a rapid increase in production,population and settlements of Neolithic Culture,especially Neolithic Liangzhu Culture in this region. But there were several abrupt climatic fluctuation stages and cooling events took place during the Holocene Megathermal. Such adverse environment and natural calamities in these stages hindered the development of the Neolithic Culture,and sometimes even destroyed neolithic culture.

Abstract:In this paper,the fuzzy set theory and model of assessment for lake (reservoir) eutrophication are established on the basis of the fuzzy characteristics of eutrophication. Furthermore, the paper proposed firstly the concept and derived method of comprehensive weight matrix of eutrophication indices. The model is also applied to assessing the eutrophication situations of 12 lakes (reservoirs) in China and the results are correspondent to the facts. Therefore,the theory and model provide not only scientific basis for the treatment and reservation of lake (reservoir) environment but also a new method for the study on assessment for lake (reservoir) eutrophication. The theory and model proposed in the paper are also adaptable to other environmental fields concerning assessment theoretically.

Abstract:In view of the study on environment of Dianshan Lake Basin,the distribution of point. non-point sources and total input of pollutants into the lake were investigated completely. The dynamic changes of the pollutants in the lake were analysed. The fuzzy matrix was used for comprehensive assessment to water quality. The trends of water eutrophication were predicated with the phosphorous model. The countermeasures of water pollution control in Dianshan Lake were suggested.

Abstract:The experiments of predation of Leptodora kindti on two common cladoceras, Diaphanosoma brachyurum and Moina micrura were carried out in Donghu Lake. Predation rate coefficients (Clearance rates) were 15.9 mL predator^-1day^-1 at 17℃,18.2 mL predator^-1day^-1 at 21℃ on Diaphanosoma brachyurum respectively, K-value was increased with temperature. Predation rate coefficient was 30.1 ml predator^-1day^-1 at 17℃ on Moina micrura. K-value of Leptodora kindti on Moina micrura was much higher than that of on Diaphanosoma brachyurum. The experimental volum (density of prey) also affected predation rate coefficients. The bigger the experimental volum,the higher the K-value.Energy flow dynamics of Leptodora kindti in plankton community in Donghu Lake were also studied. Energy of predation of Leptodora kindti on micro-cladoceras was 2.5 J m^-3day^-1 in Donghu Lake.The relationships between predation of Leptodora kindti and population change dynamics of micro-cladoceras were discussed.

Abstract:Two hundred and nine samples were collected to study Coilia mystus. It is found that the maximum body length and weight are 182mm and 23.4g respectively in commercial stock. The minimum body length and weight 94mm and 3.5g respectively, and the individual average K value 3.15×10⁴. The relationship between body length and body weight of Coilia mystus may be expressed as W=1.174×10^-5Z,^2.773.The individual average absolute fecundity and maturity coefficient of female are 7403.48 eggs and 18.92% respectively. The individual average maturity coefficient of male is 8.02%. The relationship between body length or body weight and absolute fecundity can be expressed as F=1.906×10²L^2.54 and F=688.13W-2119.68 respectivaly.

Abstract:The principles and benefits of the physic-ecological engineering (PEE) for improving drinking water quality in a lake are dealt with a sample experimental engineering in water source area of Mashan Drinking Water Plant of Wuxi City in Taihu Lake. The PEE may be used in principle for different conditions of depth, water quality.bottom sediment and wind wave.The PEE has its main objects of reducing algae concentration and improving the hydrochemical indecies of water quality in enclosed intake area of a water supply plant, including two parts of physical and ecological engineering. During the experiment of two years, the technology and management of the PEE have been much improved and experienced many time of storms and strong wind waves.The PEE may effectively reduce the algae concentration and improve the water quality. The mean rate of reducing algae concentration is more than 59-78%;the rates of reducing of turbidity and concentrations of TN,TP,NH₄⁺-N,BOD₅ and CODM_Mn are 9—40%,24—45%,2—24%,5—70%,9—61%,and 10—25% respectively. Using a special technology, the Eichhoma irassipes solms may maintain its growth under strong wave condition on the open lake surface,and its productivity in summer accounts 507 g/(m₂·d), which lead to purifying the water and restrain the algae growth. The PEE may reduce the chlorine expenditure and increase the drinking water output without the limitation caused by water bloom in lake.

Abstract:The impacts of the Three-Gorge Project are summarized in this paper from the viewpoint of the whole river basin and system ecology. Among the impacts on aquatic ecosystem and fishery of the Changjiang River basin,emphasis is placed on the survival of certain precious and rare species, such as the indigenous River Dolphin, Lipotes vexillifer. Impacts on terrestrial ecosystem include the ecological changes of the inundated, agricultural land,and the carrying capacity of the land for the resettled population in the upper reaches of the river and changes of the environment of lowland district and lowlying rice fields in the middle and lower reaches. Impacts on the surrounding geology and safety of the reservoir area include mud-rock flow,land slide and earthquake. Impacts on estuarine ecology involves increasing salination of water and soil, erosion of coastline, and the security of Shanghai city. The impacts on the cultural landscape of the Three-Gorge area are also highlighted.Through the overall and systematic analysis,the conclusion is drawn that there are both advantageous and disadvantageous aspects in the effects of the Three-Gorge Project on ecology and environment, but the disadvantageous effects are by far the greater. In order to promote what is beneficial and to reduce what is harmful,a large amount of funds has to be invested and a series of remedial measures must be taken. Further survey and studies on some of the long-term impacts which are difficult to be foreseen at present should be carried out.