PRELIMINARY STUDY ON FLASH FLOODS IN TARIM RIVER BASIN

Flashfloodsaretheimportanteventsofthehydrologicalregimeofriversinaridareas.IntheTarilncaver(Fig.1),northwesternChina,flashfledarebeingmonitored.TheobSerVeddataandinvestigationdemonstratethedifferenceintime,place,frequencyandintensityoftheiroccurrences.Therearethreet~offlagescommontotheThermcaverbasin.AlmOSteveryyea-rhighwateroccursinmonthesofJuly,AugUstandseptembercausedbyablationrunoff.However,themostdamagingflowSarefromoccasionalflashfindsbyinstenserainstormandglacierlakeoutburstflags(…     

The flood of the Nenjiang river and the Songhua river in 1998 and the comprehensive management of the river basins

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Assessment of point and nonpoint sources pollution in Songhua River Basin,Northeast China by using revised water quality model

Individual participation of pollutants in the pollution load should be estimated even if roughly for the appropriate environmental management of a river basin. It is difficult to identify the sources and to quantify the load, especially in modeling nonpoint source. In this study a revised model was established by integrating point and nonpoint sources into one-dimensional Streeter-Phelps (S-P) model on the basis of real-time hydrologic data and surface water quality monitoring data in the Jilin Reach of the Songhua River Basin. Chemical oxygen demand (COD) and ammonia nitrogen (NH_3-N) loads were estimated. Results showed that COD loads of point source and nonpoint source were 134 958 t/yr and 86 209 t/yr, accounting for 61.02% and 38.98% of total loads, respectively. NH_3-N loads of point source and nonpoint source were 16 739 t/yr and 14 272 t/yr, accounting for 53.98% and 46.02%, respectively. Point source pollution was stronger than nonpoint source pollution in the study area at present. The water quality of upstream was better than that of downstream of the rivers and cities. It is indispensable to treat industrial wastewater and municipal sewage out of point sources, to adopt the best management practices to control diffuse pollutants from agricultural land and urban surface runoff in improving water quality of the Songhua River Basin. The revised S-P model can be successfully used to identify pollution source and quantify point source and nonpoint source loads by calibrating and validating.     

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 210 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 μm) contribution30%, Zr/Rb ratio1.5, and magnetic susceptibility16 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.     

Dynamic variation of nitrogen content in the Second Songhua River

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Stable isotopes in precipitation in Xilin River Basin, northern China and their implications

Under the increasing pressure of water shortage and steppe degradation,information on the hydrological cycle in steppe region in Inner Mongolia,China is urgently needed.An intensive investigation of the temporal variations ofδD andδ1 8O in precipitation was conducted in 2007-2008 in the Xilin River Basin,Inner Mongolia in the northern China.TheδD andδ1 8O values for 54 precipitation samples range from+1.1‰to-34.7‰and-3.0‰to -269‰,respectively.This wide range indicates that stable isotopes in precipitation are primarily controlled by different condensation mechanisms as a function of air temperature and varying sources of vapor.The relationship between δD andδ1 8 O defined a well constrained line given by δD =7.89 δ18O+9.5,which is nearly identical to the Meteoric Water Line in the northern China.The temperature effect is clearly displayed in this area.The results of backward tra- jectory of each precipitation day show that the vapor of the precipitation in cold season(October to March)mainly originates from the west while the moisture source is more complicated in warm season(April to September).A light precipitation amount effect existes at the precipitation event scale in this area.The vapor source of precipitation with higher d-excesses are mainly from the west wind or neighboring inland area and precipitation with lower d-excesses from a monsoon source from the southeastern China.     

Hydrologic/hydraulic modelling and flood risk analysis for the West Tiaoxi Catchment, Taihu Lake Region, China

Located in the headwater upstream of the Taihu Lake region, which is a densely populated and economically developed area in China, the West Tiaoxi River catchment is a frequently food-hit area due to its nature and climatic characteristics. During the last several decades, more than ten catastrophic floods happened in this area, causing huge economic losses. Since 1990, due to the increasing property vulnerability to flood hazard, the disasters were even more serious than before, and economic losses increased year by year. Thus, there have great importance to study flood behaviors, flood risks and their consequences. In this paper the hydrologic/hydraulic modelling is presented firstly. It is the method to study the relationship between rainfall and runoff and the flood propagation process. Secondly, the author gives the summary of the current study methods for flood risk assessment. The West Tiaoxi River catchment has a long history of the construction of polders and hydraulic engineering. Most farmlands have been protected against floods. So the combination method has been used to obtain the real risk area. The results have been obtained by using this method, which, the authors think, will be used in disaster preparedness, property insurance etc. Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 49671028) and Deutsche Forschungsgemeinschaft (DFG). Biography: XU Peng-zhu (1965 —), male, a native of Funing County of Jiangsu Province, associate researcher. His research interests include hydrology and water resources, numerical modelling, and application of GIS to hydrology.     

近55年来澜沧江流域降水时空变化特征分析

本文利用澜沧江流域及周边共30个气象站点1960-2014年的逐月降水数据,采用气候倾向率、Mann-Kendall趋势检验、Morlet小波分析、Co-Kriging插值以及重心模型等方法,分析了澜沧江流域降水的时空变化特征。结果表明：① 分析时段内全区、北部和中部年降水量呈现增加趋势,南部年降水量出现减少趋势。春季全区、北部、中部和南部降水均呈增加趋势;夏季均呈减少趋势;秋季全区和南部降水呈现减少趋势,北部和中部呈增加趋势;冬季全区、中部和南部呈下降趋势,只有北部呈增加趋势。② 近55年来,全区包括北部、中部和南部年降水都存在近29年、近22年和5-10年左右的周期,这3个周期在分析时段内表现很稳定,具有全域性。全区、北部和南部还存在明显的13年左右的周期,中部1975年前和1995年后也存在13年左右的周期,北部1975年前存在明显的7-10年的周期,1995年后,7-10年的周期表现也比较稳定。降水量变化的第一主周期是近29年,第二主周期是近22年。③ 澜沧江流域多年平均降水量由南部向北部减少,流域南部降水最多,多年平均降水量在1200 mm以上,中部多年平均降水量处于800~1100 mm,北部多年平均降水量多小于800 mm,大部分在400~800 mm;澜沧江流域年降水重心和月降水重心都集中在中部,其中11月的降水重心迁移距离最大,向东南方向迁移了131.82 km。从季节来看,春季、夏季和秋季降水重心向东南迁移,冬季的向西北方向迁移,雨季降水重心相对比较集中,旱季降水重心相对 比较分散。     

Using modified Soil Conservation Service curve number method to simulate the role of forest in flood control in the upper reach of the Tingjiang River in China

To improve flood control efficiency and increase urban resilience to flooding, the impacts of forest type change on flood control in the upper reach of the Tingjiang River (URTR) were evaluated by a modified model based on the Soil Conservation Service curve number (SCS-CN) method. Parameters of the model were selected and determined according to the comprehensive analysis of model evaluation indexes. The first simulation of forest reconstruction scenario, namely a coniferous forest covering 59.35 km² is replaced by a broad-leaved forest showed no significant impact on the flood reduction in the URTR. The second simulation was added with 61.75 km² bamboo forest replaced by broad-leaved forest, the reduction of flood peak discharge and flood volume could be improved significantly. Specifically, flood peak discharge of 10-year return period event was reduced to 7-year event, and the reduction rate of small flood was 21%-28%. Moreover, the flood volume was reduced by 9%-14% and 18%-35% for moderate floods and small floods, respectively. The results suggest that the bamboo forest reconstruction is an effective control solution for small to moderate flood in the URTR, the effect of forest conversion on flood volume is increasingly reduced as the rainfall amount increases to more extreme magnitude. Using a hydrological model with scenarios analysis is an effective simulation approach in investigating the relationship between forest type change and flood control. This method would provide reliable support for flood control and disaster mitigation in mountainous cities.     

A STUDY ON REGULARITY OF DROUGHT AND FLOOD IN THE CHANGJIANG RIVER VALLEY DURING LAST 10 CENTURIES

According to historical records, there are 264 drought and flood years, occurred in the upper and middle reaches of the Changjiang (Yangtze) River during last 1020 years from 961 to 1980. The evolutionary law and developing trend of drought and flood years are studied. The distribution of drought and flood years are non-uniform and the dry and flood seasons in a year are concentrated. At the angle of monsoon circulation, at present the climate in the upper and middle reaches of the Changjiang River is just in the late stage of frequent drought period and the early stage of least flood period. In addition, the cycle of drought and flood and the feature of drought and flood occurred in the upper, middle and lower reaches of the Changjiang River are analyzed. It shows that the short period less than 10 years is in the majority, and the drought and flood occurred most frequently in the middle and lower reaches of the Changjiang River.     

Flood and waterlogging monitoring over Huaihe River Basin by AMSR-E data analysis

In this paper, we investigated the potential of Advanced Microwave Scanning Radiometer for Earth Observation System （AMSR-E） for flood monitoring. The proposed approach was based on the polarized ratio index （PRI）, which was computed by using AMSR-E data at 37GHz, vertically and horizontally polarized brightness temperature values and the water surface fraction （WSF） got by using the PRI at 37GHz. Moderate Resolution Imaging Spectroradiometer （MODIS） data were used to validate the WSF values. The analysis of flood and waterlogging using the WSF map on July 6, 2003 indicates that the use of WSF for flood and waterlogging disaster assessment is feasible. Utilizing the correlation of WSF derived from AMSR-E and water area derived from MODIS, the water area of the Huaihe River Basin were computed by only using AMSR-E data in the summer of 2003, which overcame the influence of cloud on water estimation using MODIS data during flood.     

A contrast analysis on the load character of the Changjiang River and the Huanghe River

According to the analysis of grain size, mineral composition and inclusion in quartz grain of the suspended and bed load sampled from the Changjiang (Yangtze) River and the Huanghe (Yellow) River, the authors reveal the differentiation of loads between the two rivers. In the Huanghe River the size of suspended load is coarser than that in the Changjiang River, while the bed load is on the contrary. Through heavy mineral analysis, the biotite content of the Huanghe River loads is much higher than that of the Changjiang River, and the monomorillonite content of the former is about two times higher than the latter. All those may be attributed to the effects of different material sources and hydraulic conditions on load. The analysis of inclusion in quartz grain definitely illustrates the environmental difference of material sources between the two rivers. In the meantime, it provides a new method in seeking source of river load. Subsidized by the National Natural Science Foundation. This paper is attributed to careful guidance from Prof. Wang Ying & Prof. Shi Yunliang.     

Evaluating Functions of Reservoirs′ Storage Capacities and Locations on Daily Peak Attenuation for Ganjiang River Basin Using Xinanjiang Model

Flooding is the most prevalent and costly natural disaster in the world and building reservoirs is one of the major structural measures for flood control and management. In this paper, a framework was proposed to evaluate functions of reservoirs′ locations and magnitudes on daily peak flow attenuation for a large basin of China, namely Ganjiang River Basin. In this study, the Xinanjiang model was adopted to simulate inflows of the reservoirs and flood hydrographs of all sub-catchments of the basin, and simple reservoir operation rules were established for calculating outflows of the reservoirs. Four reservoirs scenarios were established to analyze reservoirs′ locations on daily peak flow attenuation. The results showed that: 1) reservoirs attenuated the peak discharges for all simulated floods, when the flood storage capacities increase as new reservoirs were built, the peak discharge attenuation by reservoirs showed an increasing tendency both in absolute and relative measures; 2) reservoirs attenuated more peak discharge relatively for small floods than for large ones; 3) reservoirs reduced the peak discharge more efficiently for the floods with single peak or multi peaks with main peak occurred first; and 4) effect of upstream reservoirs on peak attenuation decreased from upper reaches to lower reaches; upstream and midstream reservoirs played important roles in decreasing peak discharge both at middle and lower reaches, and downstream reservoirs had less effect on large peak discharge attenuation at outlet of the basin. The proposed framework of evaluating functions of multiple reservoirs′ storage capacities and locations on peak attenuation is valuable for flood control planning and management at basin scale.     

淮河流域洪涝变化混沌演化特征研究

本文在淮河流域洪涝变化分形特征、吸引子维数研究的基础上,以相空间重构为理论,通过Lyaponov指数论证了淮河流域洪涝变化的混沌性和耗散性,分析了洪涝变化的混沌演化特征.     

SEAWATER INTRUSION TYPES AND REGIONAL DIVISIONS IN THE SOUTHERN COAST OF LAIZHOU BAY

The southern coast of Laizhou Bay, Bohai Sea, is one of the areas in China most seriously impacted by seawater intrusion. Based on the sources of intruding waterbedies, seawater intrusion can be divided into two types: intrusion of saline water derived from modern seawater, and intrusion of subsurface brine and saline water derived from paleo-seawater in shallow Quaternary sediments. There are some distinct differences in their formation, mechanism and damage. The subsurface brine intrusion is a special type, which can cause very serious disaster. The coastal landform and the Quaternary hydrogeological environment are predominant factors in the classification of seawater intrusion types. Various coastal environments in different coastal sections result in three types of intrusion: seawater intrusion, saline groundwater intrusion, and mixed seawater and saline water intrusion, in the southern coast of Laizhou Bay, which can be divided into four areas: the sea-water intrusion area in the northern Laizhou City coast, the mixed seawater and saline groundwater intrusion area in the Baisha River-Jiaolai River mouth plain area, the mixed seawater and saline groundwater intrusion area in the Weihe River mouth plain area northern Changyi county coast, and the saline ground-water intrusion area in the northern Shouguang plains.     

ENSO cycle and climate anomaly in China

The inter-annual variability of the tropical Pacific Subsurface Ocean Temperature Anomaly (SOTA) and the associated anomalous atmospheric circulation over the Asian North Pacific during the El Ni o-Southern Oscillation (ENSO) were investigated using National Centers for Environmental Prediction/ National Center for Atmospheric Research (NCEP/NCAR) atmospheric reanalysis data and simple ocean data simulation (SODA). The relationship between the ENSO and the climate of China was revealed. The main results indicated the following: 1) there are two ENSO modes acting on the subsurface tropical Pacific. The first mode is related to the mature phase of ENSO, which mainly appears during winter. The second mode is associated with a transition stage of the ENSO developing or decaying, which mainly occurs during summer; 2) during the mature phase of El Ni o, the meridionality of the atmosphere in the mid-high latitude increases, the Aleutian low and high pressure ridge over Lake Baikal strengthens, northerly winds prevail in northern China, and precipitation in northern China decreases significantly. The ridge of the Ural High strengthens during the decaying phase of El Ni o, as atmospheric circulation is sustained during winter, and the northerly wind anomaly appears in northern China during summer. Due to the ascending branch of the Walker circulation over the western Pacific, the western Pacific Subtropical High becomes weaker, and south-southeasterly winds prevail over southern China. As a result, less rainfall occurs over northern China and more rainfall over the Changjiang River basin and the southwestern and eastern region of Inner Mongolia. The flood disaster that occurred south of Changjiang River can be attributed to this. The La Ni a event causes an opposite, but weaker effect; 3) the ENSO cycle can influence climate anomalies within China via zonal and meridional heat transport. This is known as the "atmospheric-bridge", where the energy anomaly within the tropical Pacific transfers to the mid-high latitude in the northern Pacific through Hadley cells and Rossby waves, and to the western Pacific-eastern Indian Ocean through Walker circulation. This research also discusses the special air-sea boundary processes during the ENSO events in the tropical Pacific, and indicates that the influence of the subsurface water of the tropical Pacific on the atmospheric circulation may be realized through the sea surface temperature anomalies of the mixed water, which contact the atmosphere and transfer the anomalous heat and moisture to the atmosphere directly. Moreover, the reason for the heavy flood within the Changjiang River during the summer of 1998 is reviewed in this paper.     

A contrast analysis on the load character of the Changjiang River and the Huanghe River

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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 El Ni?o 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 Ni?o events,in El Ni?o 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,respectively.     

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