北部湾江洪扇贝养殖区的污损生物

2006年8月至2007年7月,对北部湾江洪扇贝养殖区的污损生物进行周年调查。结果表明:该海区养殖网笼的污损生物有8门20种,优势种为藤壶、钩虾、苔藓虫,其次是翡翠贻贝、牡蛎、海鞘、大型藻类和水螅。污损生物附着高峰在8、11和12月,1月的附着数量最少;藤壶附着高峰在8、11和12月,附着生物量占污损生物总量的56.0%,是养殖区污损生物防除的重点对象;钩虾附着高峰出现在8、9月,12和2月附着量也较高,其生物量占污损生物总量的18.0%;草苔虫附着高峰出现在4月,其生物量占污损生物总量的8.4%。污损生物附着量呈现由表层向底层递减的趋势。

Characteristics of Drought and Flood in Zhejiang Province,East China:Past and Future

On the basis of large amount of historical and measured data, this paper analyzed the regional, periodic, frequency, continuing, and response characteristics of droughts and floods in Zhejiang and proposed the conception of ratio of peak runoff. Main characteristics of droughts and floods in Zhejiang are as follows： 1） The western Zhejiang region is plum rain major control area, and the eastern coastal region of Zhejiang is typhoon major control area. 2） Within a long period in the future, Zhejiang will be in the long period that features droughts. 3） In Zhejiang the 17th century was frequent drought and flood period, the 16th, 19th, and 20th centuries were normal periods, while the 18th century was spasmodic drought and flood period. 4） The severe and medium floods in Zhejiang were all centered around the M-or m-year of the 11-year sunspot activity period. 5） There are biggish years of annual runoff occurred in E1 Nifio year （E） or the following year （E＋1） in Zhejiang. The near future evolution trend of droughts and floods in Zhejiang is as follows： 1） Within a relatively long period in the future, Zhejiang Province will be in the long period of mostly drought years. 2） Between 1999 and 2009 this area will feature drought years mainly, while the period of 2010-2020 will feature flood years mostly. 3） Zhejiang has a good response to the sunspot activities, and the years around 2009, 2015, and 2020 must be given due attention, especially around 2020 there might be an extremely severe flood year in Zhejiang. 4） Floods in Zhejiang have good response to El Nifio events, in El Nifio year or the following year much attention must be paid to. And 5） In the future, the first, second, and third severe typhoon years in Zhejiang will be 2009. 2012. and 2015. resnectivelv.

Trends of Extreme Flood Events in the Pearl River Basin during 1951-2010

The study investigated the trend of extreme flood events in the Pearl River basin during 1951-2010. Stream flow data at 23 gauging stations were used for the study. The Pearson type III distribution was selected for the flood frequency analysis. Results indicate that extreme flood events increase significantly in the Pearl River Basin since 1980. At the 23 gauging stations, there are 16 (70%) stations show positive (increasing) trends in 1981-2010. Most of the 16 stations are located along the West River and North River. While 7 (30%) stations show negative (decreasing) trends, and are found in the East River and the southeast region of the West River Basin.

Mountain Effect and Differences in Storm Floods between Northern and Southern Sources of the Songhua River Basin

In this study, the differences in annual rainstorm changes in the Second Songhua River Basin and the Nenjiang River basin and their causes were compared from the perspective of mountain effects. The following results were drawn: (1) Altitude effect is the primary factor leading to increased rainstorms in the southern source; (2) Slope effect primarily leads to differences of the weather systems in the two sources, and thus cause the difference of the rainstorms; (3) Slope effect is responsible for the greater fluctuation in the observed floods in the southern source. These landform differences eventually lead to the differences in the characteristics of floods in the southern and northern sources. Commensurability method was used to identify the period of rainstorms in the southern and northern sources. The results showed that although rainstorms do not appear at the same time in the two sources they are characteristic of a 10 years' period in both areas. These results can serve as hydrological references for flood control and long-term flood disaster predictions.

Exploration on ecological regulation of the reservoirs

Reservoir regulation process in the Yangtze River basin is mainly divided into two types of flood regulation and initiating benefit regulation. The present reservoir management system and operation mode are mainly for dealing with or coordinating of flood control and benefit initiation as well as benefit distribution among various beneficial functions. From the view point of river ecosystem protection, the current regulation mode has two kinds of problems: firstly, most of the reservoir regulation plans do not consider ecosystem protection at downstream of dams and needs of environment protection in reservoir areas; secondly, integrated regulation or management of water resources is ignored. It is very necessary to improve reservoir regulation mode, bearing problems faced by regulation of the Three Gorges reservoir and issues related to cascade development and regulation in Tuojiang and Minjiang River basins in mind. In accordance with the concept of scientific development, and the philosophy of "ensuring a healthy Yangtze River and promoting the harmony between human and water", taking flood control, benefit initiation and eco-system as a whole, this paper put forward the basic consideration to improve reservoir regulation as follows: on the basis of requirements of ecosystem protection at downstream of dams and needs of environment protection in reservoir areas, we should bring the functions of reservoir such as flood control and benefit initiation into full play, control the negative influence to the ecosystem at downstream of dams and the environment in reservoir areas in an endurable scope, and restore the ecosystem and the environment step by step. This paper put forward the relevant regulation process aiming at the idiographic problems such as protection of ecosystem at downstream of dams and environment in reservoir areas, protection of aquatic wildlife species and fish species, regulation of sediment and protection of wetland.

Potential control of climatic changes on flood events in the Yangtze Delta during1100-2002

Wide collection on the historic records of the climatic changes and flood events is performed in the Yangtze Delta. Man-Kendall (MK) method is applied to explore the changing trends of the time series of the flood discharge and the maximum high summer temperature. The research results indicate that the flood magnitudes increased during the transition from the medieval warm interval into the early Little Ice Age. Fluctuating climate changes of the Little Ice Age characterized by arid climate events followed by the humid and cold climate conditions give rise to the frequent flood hazards. Low-lying terrain made the study region prone to the flood hazards, storm tide and typhoon. MK analysis reveals that the jumping point of the time series of the flood discharge changes occurred in the mid-1960s, that of the maximum summer temperature changes in the mid-1990s, and the exact jump point in 1993. The flood discharge changes are on negative trend before the 1990s, they are on positive tendency after the 1990s; the maximum high summer temperature changes are on negative trend before the 1990s and on positive tendency after the 1990s. These results indicate that the trend of flood discharge matches that of the maximum high summer temperature in the Yangtze Delta. The occurrence probability of the maximum high summer temperature will be increasing under the climatic warming scenario and which will in turn increase the occurrence probability of the flood events. More active solar action epochs and the higher sea surface temperature index (SST index) of the south Pacific Ocean area lying between 4 o N-4 o S and 150 o W-90 o W correspond to increased annual precipitation, flood discharge and occurrence frequency of floods in the Yangtze Delta. This is partly because the intensified solar activities and the higher SST index give rise to accelerated hydrological circulation from ocean surface to the continent, resulting in increased precipitation on the continent.

A Typical Mode of Seasonal Circulation Transition: A Climatic View of the Abrupt Transition from Drought to Flood over the Middle and Lower Reaches of the Yangtze River Valley in the Late Spring and Early Summer of 2011

In this study, the seasonal transition of precipitation over the middle and lower reaches of the Yang-tze River Valley (YRV) from late spring to early summer is investigated. The results show that the seasonal transition of precipitation exhibits multi-modes. One of these modes is characterized by an abrupt transition from drought to flood (ATDF) over the middle and lower reaches of the YRV in the seasonal transition of precipitation. It is shown that the ATDF event from May to June 2011 is simply one prominent case of the ATDF mode. The ATDF mode exhibits an obvious decadal variability. The mode has occurred more frequently since 1979, and its amplitude has apparently strengthened since 1994. From the climatic view, the ATDF mode configures a typical seasonal circulation transition from winter to summer, for which the winter circulations are prolonged, and the summer circulations with the rainy season are built up early over the YRV.

Mechanism and Forecasting Methods for Severe Droughts and Floods in Songhua River Basin in China

The influence of various factors, mechanisms, and principles affecting runoff are summarized as periodic law, random law, and basin-wide law. Periodic law is restricted by astronomical factors, random law is restricted by atmospheric circulation, and basin-wide law is restricted by underlying surface. The commensurability method was used to identify the almost period law, the wave method was applied to deducing the random law, and the precursor method was applied in order to forecast runoff magnitude for the current year. These three methods can be used to assess each other and to forecast runoff. The system can also be applied to forecasting wet years, normal years and dry years for a particular year as well as forecasting years when floods with similar characteristics of previous floods, can be expected. Based on hydrological climate data of Baishan (1933-2009) and Nierji (1886-2009) in the Songhua River Basin, the forecasting results for 2010 show that it was a wet year in the Baishan Reservoir, similar to the year of 1995; it was a secondary dry year in the Nierji Reservoir, similar to the year of 1980. The actual water inflow into the Baishan Reservoir was 1.178 × 10 10 m 3 in 2010, which was markedly higher than average inflows, ranking as the second highest in history since records began. The actual water inflow at the Nierji station in 2010 was 9.96 × 10 9 m 3 , which was lower than the average over a period of many years. These results indicate a preliminary conclusion that the methods proposed in this paper have been proved to be reasonable and reliable, which will encourage the application of the chief reporter release system for each basin. This system was also used to forecast inflows for 2011, indicating a secondary wet year for the Baishan Reservoir in 2011, similar to that experienced in 1991. A secondary wet year was also forecast for the Nierji station in 2011, similar to that experienced during 1983. According to the nature of influencing factors, mechanisms and forecasting methods and the service objects, mid-to long-term hydrological forecasting can be divided into two classes:mid-to long-term runoff forecasting, and severe floods and droughts forecasting. The former can be applied to quantitative forecasting of runoff, which has important applications for water release schedules. The latter, i.e., qualitative disaster forecasting, is important for flood control and drought relief. Practical methods for forecasting severe droughts and floods are discussed in this paper.

High resolution records of flood deposition in the mud area off the Changjiang River mouth during the past century

This paper presents a paleoflood study to determine the flood frequency of the Changjiang River, based on core cj0702, taken from the Changjiang River subaqueous delta. We identified flood deposits by means of high-resolution grain-size variation, sensitive population, geochemical indexes and magnetic susceptibility. The core covers a time span of 120 years by 21~pb dating and was sampled at 1-2 cm intervals. Grain size, geochemical elements, and physical parameters were analyzed. The results indicate that the sediment of the core is mainly composed of silt and clay, as well as groups of interbedded silt, clay silt, and clay. Vertically, the grain size pattern was controlled by seasonal variations in water discharge and by the sediment input in winter from the abandoned Huanghe River delta. River flooding caused extreme values in all our measured parameters. We identified more than 20 flood events that occurred since 1887 using the physical parameter analysis method. The environmentally sensitive component of sediment grain size （14.32-96.39 gm） contribution〉30%, Zr/Rb ratio〉l.5, and magnetic susceptibility〉16 were selected as the criteria for flood identification generally. We also found that floods that had taken place in the upstream, midstream, or downstream parts of the river were clearly identified by these indexes while the large-scale floods that covered the whole drainage area did not leave clear indications in the sediment record. This study for identification of flood events is of great significance for understanding hyperpycnal current sedimentation as well as for forecasting of floods.

Projecting Spatial Patterns of Flood Hazard: Recent Climate and Future Changes over Yangtze River Basin

Projection of hazard changes in climate extremes is critical to assessing the potential impacts of climate change on human and natural systems. Using simulations of providing regional climates for impacts studies, five indicators (rainstorm days, maximum 3-day precipitation, elevation, gradient and distance from river or lake) were selected to project the spatial patterns of flood hazard over Yangtze River Basin for the baseline period (1961– 1990) and future (2011–2100) under SRES B2 scenario. The results showed the mean annual rainstorm days over the basin by the near-term, mid-term and long-term would increase from 3.9 days to 4.7, 4.9 and 5.1 days, and the mean annual maximum 3-day precipitation from 122 mm to 143, 146 and 149 mm, respectively. The flood hazard of the basin would become more severe, especially in the middle and lower reaches. Flood hazard grade 5 by the nearterm, mid-term and long-term would extend from 10.99% to 25.46, 28.14 and 29.75%, respectively.

Quantitative Simulation on Soil Moisture Contents of Two Typical Vegetation Communities in Sanjiang Plain,China

Different types of vegetation occupy different geomorphology and water gradient environments in the San- jiang Plain, indicating that the soil moisture dynamics and water balance patterns of the different vegetation communi- ties might differ from each other. In this paper, a lowland system, perpendicular to the Nongjiang River in the Honghe National Nature Reserve （HNNR）, was selected as the study area. The area was occupied by the non-wetland plant forest and the typical wetland plant meadow. The Microsoft Windows-based finite element analysis software package for simulating water, heat, and solute transport in variably saturated porous media （HYDRUS）, which can quantita- tively simulate water, heat, and/or solute movement in variably-saturated porous media, was used to simulate soil moisture dynamics in the root zone （20-40 cm） of those two plant communities during the growing season in 2005. The simulation results for soil moisture were in a good agreement with measured data, with the coefficient of determi- nation （R2） of 0.44-0.69 and root mean square error （RMSE） ranging between 0.0291 cm3/cm3 and 0.0457 cm3/cm3, and index of agreement （d） being from I）.612 to 0.968. During the study period, the volumetric soil moisture content of meadow increased with the depth and its coefficient of variation decreased with the depth （from 20 cm to 40 cm）, while under the forest the soil moisture content at different depths varied irregularly. The calculated result of water budget showed that the water budget deficit of the meadow was higher than that of the forest, suggesting that the meadow is more likely to suffer from water stress than the forest. The quantitative simulation by HYDRUS in this study did not take surface runoff and plant growth processes into account. Improved root water uptake and surface runoff models will be needed for higher accuracy in further researches.

The flood control and regulation of Three Gorges Project

The important role of Three Gorges Project (TGP) in the flood management of the Yangtze River Basin is summarized.The Optimal Regulation Schemes of the Three Gorge Reservoir is briefly described.The flood regulation effect of TGP is analyzed.Typical issues related to reservoir operation for flood regulation are discussed and suggestions are put forward for the future work.

Decision Support System for Flood Control with Applications to Jiangxi Province

Affected by the climatic fluctuation and human activities, significant changes of the flood control situation are taking place in China. In the new century, the flood control systems have to face a series of challenges. In this paper, we design fa decision support system (DSS) for flood control based on its requirements. The DSS has been applied to decision-making for flood control in Jiangxi province, and play an important role in the flood control in the recent two years. Finally, we plot the further improvement on the DSS so that it will make more contribution in the flood control.

The Natural Forest Protection Program in China： A Contingent Valuation Study in Heilongjiang Province

In 1998, the Chinese Government implemented the NFPP （Natural Forest Protection Program）, which included logging restrictions, protected areas, replanting, and a range of other policies aimed at safeguarding the state of the country＇s forests and reducing the risk of erosion and flooding. A second phase of this program is currently being discussed. In this paper, contingent valuation is used to estimate the WTP （willingness to pay） for maintaining the program among the inhabitants in Heilongjiang Province in northern China. The results show that, even with fairly conservative assumptions, the aggregated WTP for maintaining the program for another five years is some 3.24 billion yuan per year. This can be compared with the current cost of the Program in the province, which is some 1.57 billion yuan per year.

The planning and comprehensive utilization of Three Gorges Project

As the most significant water project,the Three Gorges Project (TGP) was designed to take care of multiple objectives for water utilization such as flood control,power generation and navigation.The implementation of the project improved the flood safety level of Jingjiang reach to more than 100-year return period,which reduced greatly the flood risk at the mid-lower reaches of Changjiang River,produce huge quantity of energy for the central,east and south China,and improved significantly the navigation conditions of Chuanjiang River.Meanwhile,the operation of the TGP in dry season which compensate the downstream water resources,will as well deepen the navigation channel and thus improve the navigation conditions in the middle river reach.With the increasing demands raised from various aspects of the society,new requirements will be made for the TGP for the purpose of harnessing,development and protection of the Yangtze River Basin.Therefore,it will be a long-term task for the operation of TGP on how to optimize the water resources utilization and implement an effective operation.

Design flood of ungauged basins based on DEM

In this paper,the northern mountainous area of Fuzhou City which is an ungauged basin has been taken for example to discuss the method of design flood calculation by means of combining the DEM(digital elevation model) and the Xin'anjiang Model(three components).The problem of estimating the parameters of the runoff model has been solved by using the parameters of the reference station.In the conflux calculation,the isochrones are obtained by DEM which helps to avoid the cumbersome work of drawing them on the map.With the establishment of the digital elevation model throughout the country,it is practically significant to use it in the hydrological estimation.

Analysis of the effect of regional lateral inflow on the flood peak of the Three Gorges Reservoir

The Three Gorges Region(TGR),located at the lower reach of the Upper Yangtze River Basin(UYRB) in China,suffers from heavy rainstorm frequently.The runoff generated from TGR composes an important part of the total flood at the famous Three Gorges Reservoir(TGRe).During the severe flood period in 1954,for example,the water from TGR accounted for up to 13.2% of the 30-days maximum flood volume of the UYRB.Considering the short and steep tributaries with rapid concentration,the regional lateral inflow(RLI) may induce more serious effect on the flood peak of the TGRe than the volume.However,hydrological data of the sparse gauge stations is too insufficient to evaluate the effect of RLI.This paper studied the impact by analyzing 880 flood events during 1956-2000.By comparing the observed hydrograph and simulated hydrograph with HEC-RAS software regarding no RLI,the effect of RLI on flood peak value and timing properties was identified and quantified.The variability of this effect among floods of different magnitudes was also analyzed.To evaluate the analysis uncertainty associated with the parameter of roughness coefficient,four sets of roughness coefficients from different research groups were employed in this study.The results showed that RLI contributes discharge of 3524 m3/s to flood peaks of the TGRe on average,with the contribution ratio of 15.9%.RLI contributes 12000 m3/s to the flood peaks larger than 50000 m3/s on average,with 25000 m3/s as its upper bound,while the contribution ratio can reach up to 50%,with an average of 20%.The variability of this effect is great among different events.Statistical analysis showed that to larger flood peak of the TGRe,RLI contributes more discharge with higher variability,and the contribution ratio and its variability are slightly larger,and events with higher contribution ratio occur more frequently.RLI can reshape the hydrograph,leading to earlier appearance of flood peak.This effect and its variability increase with the contribution ratio.This study has revealed that RLI plays an important role in large flood peak of the TGRe,which calls for more reliable flood forecasting methods to prolong the forecast lead time and improve the accuracy for the safety of the Three Gorges Dam and the protection of its lower reaches during severe flood disaster period.

The Eastern China flood of June 2015 and its causes

Two record-breaking rainfalls in late June of 2015 led to widespread flooding in Eastern China, espe- cially over the Yangtze River Delta, and this in turn led to huge economic losses. Analysis suggests that the E1 Nifio- like sea surface temperature pattern during that month facilitated an intensified and southwestward-shifted west- ern Pacific subtropical high and enhanced water vapor convergence along the Meiyu front, which provided a favorable environment for the occurrence of heavy rainfall over Eastern China. Meanwhile, two midlatitude troughs were successively formed over East Asia in the second half of the month as a consequence of the downstream energy dispersions of two midlatitude blockings. These configu- rations facilitated the southward intrusion of the extrat- ropical high potential vorticity toward the Meiyu front. In this way, the ascent was enhanced along the Meiyu front over Eastern China, and the occurrence of heavy rainfalls was triggered. Moreover, a tropical intraseasonal active convection propagated northward and also contributed constructively to the heavy rainfall.

Fluctuations in the tidal limit of the Yangtze River estuary in the last decade

The tidal limit is the key interface indicating whether water levels will be affected by tidal waves, which is of great significance to navigation safety and regional flood control. Due to limitations in research methods, recent changes in the Yangtze River tidal limit, caused by sea level rise and large-scale engineering projects, urgently need to be studied. In this study,spectrum analysis was undertaken on measured water level data from downstream Yangtze River hydrological stations from2007 to 2016. The bounds of the tidal limit were identified through comparisons between the spectra and red noise curves, and the fluctuation range and characteristics were summarized. The results showed that:(1) During the extremely dry period, when the flow rate at Jiujiang station was about 8440 m3 s-1, the tidal limit was near Jiujiang; whereas during the flood season, when the flow rate at Jiujiang station was about 66700 m3 s-1, the tidal limit was between Zongyang Sluice and Chikou station.(2)From the upper to lower reach, the effect of the Jiujiang flow rate on the tidal limit weakens, while the effect of the Nanjing tidal range increases. The tidal limit fluctuates under similar flow rates and tidal ranges, and the fluctuation range increases with increasing flow rate and decreasing tidal range.(3) With the continued influence of rising sea levels and construction in river basin estuaries, the tidal limit may move further upstream.