Abstract:Another flood as heavy as that of 1954 and 1991 takes place in the Taihu Basin during the Plum Rain period, 1999.The precipitation amounts to 672.8mm, which is the greatest ever recorded since 1928 in the basin.The water level in many stations rises up sharply, all higher than warning level.Some stations have recorded the highest levels in history.On July 8, the water level in Taihu lake (averaged by 5 stations around the Taihu Lake) reaches 5.08m, which is 0.42m and 0.28m higher than those recorded in 1954 and 1991.The period that the level ex-ceedsanti-flood level (4.66m) has lasted more than one month, resulting a drowned area of more than 304 thousand ha.The direct loss has targeted 13.2 billion yuan (RMB).After first-hand investigation in situ and analysising remote sensing data during the flood period, the authors bring forward sorhe suggestion on the intergrated harnessing in the basin.

Abstract:The monscMDn-raining season in the Taihu Basin, started on June 7,1999, lasted for 43 days.Estimates revealed that the total average rainfall reached 670mm, which was 3 times higher as compared with normal years and closely and/or more rated at a return period of 1 in 100 years.Comparing with the flooding in 1954 and 1991, the rainfalls of 7-day, 15-day, 30-day, 45-day, 60-day and 90-day in 1999 exceeded the historical valuevS ever recorded.The rainfall wavs unevenly distributed, being heavier in south than in north of the Basin,i.e.the precipitations in districts of West Zhejiang Province, Taihu Lake, Hangjiahu Lake, Pudong and Puxi(Shanghai) were obviously larger than of that of other districts.The highest water level in Taihu Lake reached 5.08m a.s.l, 0.29m up to the historic 4.79m ever recorded during the 1991 flood.The 1999 catastrophic flood had brought a loss of 131×10⁸ RMB to the basin economy.It impels us to reexamine the regulation of the water conservancy project, avs well as the relation between flood storage and discharge, flood control in overall basin and flood discharge in each district.Moreover, some suggestions on the reasonable management of key projects in the basin, and the amendments of flood control planning in the 21 century are put forward.

Abstract:Taihu lake basin is an phialiform area of lower area in center with higher around.Due to the effect of tide, the difficulty of driainage may arise.With the high development of economy recent years, the mode of land utilization chagned accordingly.This affects the flood disaster signally.In this article, through the comparison and analysis of some aspects including rain-storm, drowned area, flood level and regulation capacities in 1954, 1991 and 1999 in Taihu Lake basin, some countermeasures on flood control are put forward.

Abstract:Based on the characteristics of flood evolution, water regime in the Taihu Basin and the task of flood control, the flood regulation scheme of the Taihu Basin has been formulated and carried out in recent ears.The flood regulation scheme should be perfected with changing landscape situations in the Basin.The benefits of flood control and waterlogging protect of harnessing projects in the Taihu Basin are distinct.A further amendment of the flood regulation scheme is required by the flood control practice.

Abstract:Erhai Lake in S.W.Ghina is a large, shallow (<20m deep) rift lake.Sediment supply comes mainly from the mountains west of the lake that reach a relative height of 2000m.Supply from the east, a relatively low limestone country, is small.Two rivers supply sediment from north and south.Bottom deposits are predominantly silty mud;coarse material supplied from the mountains has been deposited on broad terraces, deltas, delta-fans, and nearshore in the lake.Deposition rates during the past 13000 years have been low, on the average 0.2 cm a^-1, which is equivalent to about 600 t a^-1, over the entire lake and is of the same order as the amount of suspended sediment present in February 1992.This points to storage of sediment on land during periods of relatively large supply (period of large rainfall, destruction of vegetation, or earthquakes) and it explains the continuing existence of the shallow lake.Average sediment deposition may have varied by a factor of 2 or 3 at most.Currents redistribute the sediment over the lake floor in flat beds extending over almost the entire lake.There is very little evidence of slumping or sliding.The composition of the sediment reflects the composition of the rocks and soils in the source areas with an additional biogenic component(mainly diatom opal).There is a relative abundance of trace elements, which may be the result of leaching on land, pollution and/or the fine grain of the sediment.

Abstract:There were many medium and small-sized lakes in the early Ming dynasty, which were linked each other by many deep or shallow canals in Jianghan plain.Along with the economic development, population growth, protective embankments in lakeside areas mushrooming and booming, there broke out more and more inundation after Chenghua(1465-1487).From the last phase of Zhengde (1506-1521) to early stage of Wanli (1573-1620),many medium-sized and small-sized lakes had been silting-up from the Yangtze River and Hanshui River, The spatial-temporal distribution of the lake evolution were different duo to the following reasons: Mire and sand from Hanshui River were deposited from the upper reaches to the lower reaches, while those from the Yangtze River were firstly silted up from the upper reaches to the lower reaches, then deposited back to the upper reaches.We can see this evolving trend clearly from the reducing and merging process of Hebosuo, an organization for levying piscatorial taxes.

Abstract:The effect of culture water replacement on resting egg formation of freshwater rotifer, Brachionus calyciflorus, was studied under conditions of population accumulative culture.The results showed that when the rotifer was cultured by batch culture method, the production and formation efficiency of resting egg were 724.3333±40.5257 ind.(6d·20mL)^-11 and 6.0361±0.3377 ind.(5×10⁶cells)^-1 (algae diet), respectively.When the water replacement was made at every two days interval, the production and formation efficiency of resting egg decreased to 637.3333±16.8028 ind.(6d·20mL)^-1 and 5.311±0.1400 ind.(5×10⁶cells^-1 (algae diet), respectively.The extent of the decline increased with the increment of water replacement frequency.There were no different effects of water replacement on the mixis and fertilization rate.The mechanism of the effects was also discussed.

Abstract:In May 1995, the kinetic parameters (V_max and K_m) of alkaline phosphatase in interstitial water, overlying water and surface water were differed significantly in Donghu Lake (Wuhan) and Yanxihu Lake(P<0.05).At Station I and HI of Donghu Lake, V_max values of overlying water were much higher than those of surface water, while in Yanxihu Lake V_max values of overlying water were much lower.At Station II in Donghu Lake, both V_max and K_m values were quite lower in overlying water, exhibiting a higher catalytic efficiency.This phenomenon might relate with the compositions of enzyme activities.In brief, a pronounced downward gradient of enzyme catalytic efficiency was observed in Donghu Lake, which was not recorded in Yanxihu Lake.Consequently, the enzymatic hydrolyzable P may contribute to the internal loading of the eutrophic lake, and stratification of kinetics and compositions of phosphatase in shallow lake is theoretically noticeable.

Abstract:The effects on embryonic development of the cherax quadricarinatus at water temperature which included seven sets of 22℃, 24℃, 26℃, 28℃, 30℃,32℃ and ambient temperature were studied by light microscope from 1997 to December, 1998.The results showed briefly in the following: The water temperature ranges from 24℃ to 30℃ were suitable for embryonic development of the shrimp, beyond this water temperature ranges, it would be dangerous or lethal to the shrimp;This optimum water temperature for embryonic development of the shrimp was 28℃ to 30℃;The development of the embryo was quite sensitive to water temperature, the higher water temperature was, the less time embryonic development spent, but embryonic survival rate was gradually decreased.

Abstract:Scenedesmus obliquus, inoculated in the carbonate hard water in the Yucheng County, Shangong Province, was observed to grow rapidly under the condition of supplementing certain salts and aeration.The experimental results revealed that saline-alkali waters water could be purified in some extent by the algae.After 36 houns culturing, the eliminating rates of 8 main ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^-, SO₄^2-, HCO₃^-, CO₃^2-) in the water respectively reached 48.5%, 5.9%, 77.5%, 74.5%, 28.2%, 46.7%, 100%, 53.1%.

Abstract:An investigation on one of the dominant species of gastropods, Bellamya aeruginosa in Houhu Lake, Wuhan was carried out from April, 1996 to March, 1997.The results showed that the population was composed of three year classes, among which the 96 year class grew most quickly, with instantaneous growth rate of dry weight (unshelled) 2.80.The annual production of the animal calculated by instantaneous growth rate method was: wet weight, 33.13 g m^-2a^-1;dry weight (unshelled), 1.932 g m^-2a^-1.The corresponding annual P/B ratios was 0.85.

Abstract:The investigation of the aquatic vegetation in Dianchi Lake has been carried out from 1995-1997.This paper described the sepcies composition, community structure, distribution, biomass and succession dynamics of aquatic vegetation in the Lake, and analyzed the interaction between the change of the aquatic vegetation and the environmental quality.Comparing with over 100 species found in the 1950s in Dianchi Lake, there are only 22 sepcies of auqatic vascular plants collected from this lake, among which Eichhornia crassipes, Alternanther phiLoxeroides, Pota-mogeton malainus and Myriophyllum spicatum are the dominant species off aquatic vegetation.The aquatic vegetation of Dianchi Lake from 1995 to 1997 could be divided into 9 associations.Due to the eutrohpication and the water pollution, the area of the aquatic vegetation decreased from 90% to 1.8% and the biomass decreased from 1363.1 g m^-2 to 136.73 g m 2during tl.last 50 years.The community structure has simplicated and deteriorated drastically, the biodiversity changed periodcally along with the succession of the major species.The Dianchi Lake has completed the transition from submerged-plant-dominant-type, and Caohai has being in the third alternative stable state which the floating plant is dominant.

Abstract:Advances in ecological stuides on zooplankton were reviewed based on the published papers and authors studies.Contents include long-term ecology, dynamics changes of zooplankton, predation ecology and effects of environmental factors such as temperature, food resources on zooplankton.Long-term studies on zooplankton are very important to understand changes of ecosystem, especially those driven by slow processes, rare or episodic events and highly variable, stable or complex processes.The major objectives of long-term investigations are to provide reliable estimates of base-line variation, to detect long-term trends in the mean level of base-line, to detect rare events and to provide information for meaningful, testable hypotheses.A lot of research results demonstrated that changes in zooplankton community structure were determined largely by fish in the water bodies, with high stocking rate of planktivorous fish, and also by predation of invertebrate animals such as some copepods.Water temperature, food resources etc.may cause a stable zooplankton community.Among the freshwater zooplankton community, Daphnia and Cyclops vicinus may be the key groups.Because Daphnia plays a key role in the top-down control of phytoplankton, and C.vicinus are key factors in aquatic food chain during the period of their maximum abundance.In addition, several research topics such as molecule biology of zooplankton, zooplankton ecology of the surface microlayer, influence of engineering water conservancy project on ecosystem and zooplankton, and batch culture of zooplankton were discusses.

Abstract:Tha Nansihu Lake has been strongly influenced by both of the Yellow River's overflow and human activities.Its forming age has not been determined for a long time.By the two sedimentary cores in the Nansihu Lake, this paper analyzed the environmenntal indexes of pigment, organic δ¹³C and C/N.The ages of the low parts in the cores are measured by ¹⁴C and sedimentation rate of the cores are determined by both of the ²¹⁰Pb and ¹³⁷Cs.Combined with the distribution of pigment, C/N and organic S13C, it can be determined that the forming age of the Nansihu lake is 2450aBP.

Abstract:Two generations of Protosalanx hyalocranius transplanted in Daoguanhe Reservoir were observed.It showed that the propagation of the fish related to climate and temperature, the observed sex ratio change related to the both behavior during propagation and there was the time and spatial diversity in propagation groups.