The Longmen-Sanmenxia reach of the middle Yellow River is one of the three major sediment sinks along the the mianstream of the Yellow River. Based on the concept of sediment budget and using the hydrometric data in the past 87 years, a study has been made on sediment storage, release and transport in this sediment sink. At the timescale of 80 years, the variation in sediment storage can be divided into four stages: (1) from 1920 to 1959, the Longmen-Sanmenxia sediment sink was in "quasi-natural" state, and sediment storage increased slowly; (2) from 1960 to 1967, due to sediment trapping of the Sanmenxia Reservoir, sedimentt storage increased rapidly; (3) from 1968 to 1985, the operational mode of the Sanmenxia reservoir was changed successively to "flood retention and sediment releasing afterwards" and "releasing sediment during high flow season and storing clear water during low flow season", sediment storage and release were nearly balanced each other; (3) from 1986 to 2006, water diversion increased rapidly, leading to an increase in sediment storage, although sediment input decreased. Within a year, sediment storage occurred during July and August, and sediment release occurred from September to the next May. During the 1800 years from 155 AD to 2006, the variation of sedimentation rate in the Longmen-Tongguan sink underwent a cycle from increase to decrease, which can be explained by the changed manner and intensity of human activities. During the "quasi-natural" stage from 1920 to 1959, the sediment storage and sediment delivery ratio in the Longmen-Sanmenxia sink were closely related with sediment and flow input to the sink.
The application of dams built upstream will change the input conditions, including water and sediment of downstream channel system, and destroy former dynamic equilibrium, so necessary adjustments are demanded for the downstream channel to adapt to the new water and sediment supply, which will lead to the downstream channel to restore its former equilibrium or reach a new equilibrium. Using about 50 years of hydrological, sediment and cross-sectional data, spatial response process of Toudaoguai cross-section to the application of dams built upstream was analyzed. The results showed that the Toudaoguai cross-section change was influenced strongly by the application of upstream dams and armoring happened and extended to the channel down the Sanhuhekou cross-section. Median diameter of sediment particle experienced a three-stage changing trend which was characterized by an increase at first, then decrease and increase again finally, since the joint application of Longyangxia, Qingtongxia and Liujiaxia reservoirs in 1986, the three-stage changing trend has become less obvious than the time period between 1969 and 1986 when only Qingtongxia and Liujiaxia reservoirs were put into operation.
Through investigation of the middle reaches of the Jinghe River, we choose the slackwater deposits for palaeohydrology study. On the basis of field survey, samples of the slackwater deposits were collected and the grain-size distribution, the magnetic susceptibility variation, the loss on ignition and the content of calcium carbonate were determined. All of these indexes showed that the slackwater deposits were typical in the study area. According to the stratigraphic correlation and cultural remains including fragments of pottery and burnt earth, we identified the corresponding palaeoflood which occurred in the late period of Longshan Culture (4200-4000 a B.P.). Supported by the hydrological technique, we reconstructed that the peak discharges of the palaeofloods were 19490-22040 m3/s. Meanwhile, reconstruction of modern gauged flood proved the hydrological method was reliable. And the relationship between drainage area and flood peak discharge illustrated that the results were reasonable. Thus, the results prolong the flood data sequence of Jinghe River and provide significant data for engineering construction, flood control and disaster alleviation in the middle reaches of the Jinghe River.
The Muzhaerte River Valley is located on the southeastern slope of the Tumur Peak, the largest center of modern glaciation in the Tianshan Mountains of China. Four sets of moraines are well-preserved in the valley and on the piedmont. The landforms contain vital information about the variation of the palaeo-environment, and studies on them make it easy to understand the change of ancient glaciers and to reconstruct the palaeo-environment in this region. Electron spin resonance (ESR) dating of a well-exposed section, end moraines and associated outwashes, fluvial sediments on the Kezibulake moraines were carried out using Ge centers in quartz grains, which are sensitive to the sunlight and grinding. Considering the principles of geomorphology and stratigraphy and the available data of the palaeo-environment, some conclusions can be drawn as follows: the first set of moraines, consisting of 3-4 end moraines, were deposited in Little Ice Age; the Tugaibieliqi end moraine was the sediment of the Neo-glacial; the Pochengzi end moraines and the Kezibulake moraines were determined to deposit in the last glaciation and in MIS6. The Pochengzi end moraines and their dates demonstrate that at least three large glacial advances occurred during the last glaciation, corresponding to MIS4, MIS3b and MIS2, respectively. Furthermore the result shows that the glaciers were compound valley ones in MIS2 and MIS3b, while they were piedmont ones in MIS4 and MIS6. The length of the ancient Muzhaerte glacier was about 92~99 km during the Pochengzi glaciation and about 120 km during the Kezibulake glaciation.
In this paper we carry out a study on the longitudinal profile of the 10 rivers in the north Tianshan Mountains, by fitting the characteristics of the river longitudinal profile using four function patterns, and analyzing the evolution process of the 10 rivers' longitudinal profile based on the stream-power incision model. We reveal the relationships between the evolution process of the river and the tectonic activity. Our study indicates that the concavity index of the Taxihe River is the greatest one among the 10 rivers, and the concavity indexes of the other rivers become small one by one in turn on both sides, so the concavity indexes of the Urumqi River and the Sikeshuhe River are the least ones comparatively. The evolution phase of the river topographic form is the pre-steady-state topography. Consequent analysis reveals that the upward-convex features of the profiles and slope-area plots can be explained by the elevation of the bedrock profile getting higher and higher and the uplift being beyond the incision around the target area.
The Shlehe River Basin is located in the western part of the Qilian Mountains, where climate is very dry. Ten boreholes were drilled at 5 sites on various types of land surface and terrain in the source areas of the Shule River valley for monitoring permafrost, and measured temperature tubes were assembled in the boreholes. According to records of borehole and measured temperature, the elevation of permafrost lower limit was determined to be 3750 m (a.s.l.) and volume of ground ice was little because loose stratum is alluvium composed of coarse soil. The permafrost state was affected by local factors obviously. Discrepancy of a slope gradient can lead to a ground temperature difference of 0.5 oC, while discrepancy of slope aspect can result in a ground temperature difference of 1.0 oC. Influences of soil water content on ground temperature of shallow layers are even greater than those of slope aspect. Discrepancy of ground condition can result in significant difference in ground temperature and depth of active layer. Contrast to permafrost of central-eastern Qilian Mountains, permafrost in the Shule River source areas is not affected by ecological processes and its formation and preservation were directly driven by climate. So the permafrost of the Shule River source areas was typical of that of arid regions.
This paper studies the changing trend of annual and seasonal mean temperature, maximum temperature, minimum temperature, precipitation and sunshine duration etc. by using the observational data of 9 meteorological stations over the Nujiang River Basin in Tibet from 1971 to 2008. It also analyzes the variation trend of meteorological elements by climatic linear trend methods, and discusses the correlation between the linear trend of elements and latitude, altitude and longitude. The results show that the annual mean temperature has increased over the Nujiang River Basin with a rate of 0.26 oC/10a during the past 40 years, which is lower than that in Northeast China and Northwest China, and is higher than that in the Huaihe River basin and South China, and similar to that over the Qinghai-Xizang Plateau. The trends of mean maximum and minimum temperatures are increasing, the trend of diurnal temperature range is significantly decreasing at a rate of (-0. 13~-0.57) oC/10a. The annual precipitation increases significantly and the linear increasing rate is 21.0mm/10a, while that in all seasons increases. The annual sunshine duration decreases over the Nujiang River Basin with a rate of -31.7 h/10a, and the maximum decrease is in summer, and the rate of decrease is greater than that in the Huanghe River basin and eastern margin of the Qinghai-Xizang Plateau. In addition, the variation of maximum frozen soil depth shows a significant declining trend over the upper reaches of the Nujiang River Basin in Tibet, resulting from the increasing soil temperature, especially in Amdo. Correlation analysis demonstrates that sunshine duration is significantly negative with precipitation (all seasons) and surface vapor pressure (in summer and autumn). Results indicate that the principal causes for the decrease of sunshine duration are the significant increase of surface vapor pressure and precipitation in most parts of the Nujiang River Basin. The correlation between total cloud amount and diurnal temperature range is negative significantly, and is positive evidently with precipitation in summer, hence the relative humidity is not the main affecting factor with the decrease of total cloud amount. The amplification of annual temperature and precipitation became greater with the increase of altitude and latitude. The linear trend of sunshine duration is positively related with longitude, and the decreasing amplitude of sunshine duration in summer and winter decreases with increasing longitude.
Based on daily temperature (maximum and minimum) and daily precipitation at 10 meteorological stations over the Yarlung Zangbo River Basin observed by the China Meteorological Administration during the 1961-2005 period, the spatial and temporal variations in climate extremes are analyzed. The results are as follows: Over the 1961-2005 period, the regionally averaged occurrence of extreme cold days and nights has significantly decreased by -0.97 and -1.94 days/decade, respectively. Over the same period, the occurrence of extreme warm days and nights has significantly increased by 1.26 and 3.03 days/decade, respectively. The diurnal temperature range (DTR) exhibits a decreasing trend (0.11 oC/decade), especially in winter, coinciding with the fact that there is a greater rise in the minimum temperature than in the maximum temperature. The decrease in the number of cold days mostly occurs in winter and autumn, while the increase in the number of warm nights and days mainly happens in summer and winter. Precipitation indices, due to the large and expected spatial variability, indicate that regionally averaged annual maximum with 1-day precipitation and consecutive dry days have no statistically significant decreasing trends. At the same time, there is no significant increase in regionally averaged daily rainfall intensity, consecutive wet days, number of heavy precipitation days and maximum annual amount for 5-day precipitation.
The precipitable water vapor, transfer flux of water vapor and divergency of transfer flux of water vapor over the Qinghai-Xizang Plateau in summer half year (from April to September) is calculated by using NCEP/NCAR reanalysis data obtained from 60 years from 1948 to 2007. The distribution and variation characteristic of precipitable water vapor in summer half year over the Qinghai-Xizang Plateau is analyzed. The transfer of water vapor over the whole plateau and its surrounding is analyzed. THe result shows that there is a significant high center of precipitable water vapor at the middle troposphere over the Qinghai-Xizang Plateau in summer half year. The characteristics of ‘ moist pool’ are significant, and there are three high centers of precipitable water vapor in the ‘moist pool’ , which are southwest, southeast and south sides of the plateau. The variation of pricipitable water vapor over the whole region is great from April to September. The velocity of moisture increase is faster than its decrease. Water vapor comes into the Qinghai-Xizang Plateau mainly through three moisture channels, which are westerly zone channel, Indian Ocean via the Bay of Bengal channel and South China Sea via the Bay of Bengal channel. The water vapor entering the plateau is mainly from the southeast plateau, the southwest plateau, and the middle Himalaya Mountains.
In this paper the spatial-temporal evolution processes of KRD land in Guizhou Province was analyzed mathematically by using 1:100000 scale digital-distribution maps of KRD land obtained by user-computer interactive interpreting method from Landsat images in 1986, 1995 and 2000. The following conclusions are obtained: (1) From 1986 to 2000, the change in total area of KRD land in Guizhou was not obvious, but the mutual transformation of different KRD types is extremely remarkable. (2) The change patterns of KRD land are divided into three kinds: simple change mode, continuous change mode and returned change mode, and characterized by continuous change mode. (3) The forward and reversion evolution processes coexist, with the ratio of the former to the latter being 82.29%, demonstrating that the situation is getting better partially and on the whole it is worsening. (4) The rate of the KRD evolution is 398.31 km2 per year, and the change rate of different type KRD land is inverse proportion to its degree of degradation. (5) The change frequencies of moderate and potential KRD land is highest and obviously higher than that of light KRD land. The regional characteristics of KRD spatial evolution and its influencing factors are analyzed, and some suggestions on comprehensive control of KRD land are put forward.
In order to analyze the contents of heavy metals (Pb, Cd, Cr, As and Hg) in agricultural surface soils, a large scale survey was conducted in Chongming Island. 28 soil samples were collected from vegetable plot, 65 samples were collected from paddy fields and 9 samples were collected from watermelon fields. Different assessment standards of heavy metals were also used for comparison. Results showed that the content of Pb, Cd, Cr, As and Hg averaged 21.597 mg·kg-1, 0.176 mg·kg-1, 69.395 mg·kg-1, 9.209 mg·kg-1 and 0.128 mg· kg-1, respectively. In comparison with the background value of soil in Shanghai, mean concentrations of heavy metals in soils all exceeded their corresponding natural background values, except for Pb and Cr. The contents of Cd, As and Hg were 33.0%, 1.2% and 26.3% higher than the background value of Shanghai, respectively. In addition, inverse distance interpolation (IDW) method was also applied to study the spatial variability of heavy metals based on GIS. The results indicated that most of agricultural soils were good, and the ratio of ecology, good soil, certified soil and disqualified soil were 1.26%, 97.14%, 1.47% and 0.12%, respectively. Taking the background value as a reference, the ratios of all the soil samples above the limit were Pb 10.1%, Cd 85.7%, Cr 27.0%, As 55.4% and Hg 55.2%, respectively. Of the three land use types, vegetable plot was polluted most seriously by heavy metals, which is probably related to the over-application of pesticides. The annual deposition fluxes of Pb, Cd, As and Hg were 7735.470 μg·m-2·a-1, 208.432 μg·m-2·a-1, 2237.738 μg·m-2·a-1 and 52.783 μg·m-2·a-1, respectively.
Large-scale and dense sediment samples and associated hydrological data were collected in July 2005 and May 2007 from submarine sectors of Chongming Eastern Shoal, Hengsha Eastern Shoal, Jiuduan Shoal and Nanhui Shoal, which are four important tidal flats located at the mouth-bar river segment of the Yangtze Estuary. Based on the above data, the grain size and related parameters, compositions, classifications in sediments and their distributed characteristics are analyzed, and then mainly impacted dynamic factors on the distributions of sediments are discussed. The results are shown as follows: sediments located at these tidal flats of the Yangtze Estuary are mainly composed of sand, silty sand and silt. The median grain size in sediments is relatively complex with a range from 2.5φ to 8φ. The distributions of sorting coefficients in sediments ranging from 1 to 2 are agreed with that of the median grain size. Moreover, it is suggested that sediments of the tidal flats is coarser, better sorted or finer, and worse sorted. The skewness and kurtosis in sediments are ranged from 0.1 to 0.8 and from 1 to 4, respectively. In addition, the distributions of the grain size parameters, including sorting coefficient, skewness and kurtosis in sediments of Chongming Eastern Shoal, Hengsha Eastern Shoal and Jiuduan Shoal are of similar characteristics because there are closely positive correlated relationships among these parameters. However, due to the location difference between Nanhui Southern Shoal and Eastern Shoal, three parameters of grain size in sediments such as sorting coefficient, skewness and kurtosis have relatively large distinctions. Moreover, the tracks of sediment transport can be described based on the distribution of sediments which may reveal sediment transport controlled by the two dominant hydrodynamic factors of current and wave. It is appreciable that coarse sediments with better sorted is subjected to dominant ebb current action and intense wave action resulted from rapidly dissipated wave energy. In addition, due to the effects of obstructed branches, guided current and broken wave actions of the Deep Water Channel Project, grain size in sediments located on two sides of the groyne is of uneven distribution characteristics.
