Glacier and snow cover distributed widely in Xinjiang, when its melt water supply to the rivers often accompanied by glacial floods, snowmelt floods, glacial lake outburst floods, glacial debris, ice and snow avalanches, snowdrift and other snow disasters. There are greater threats on the local urban residence and the important defense lines because of these disasters. The extent and range of the ice and snow disasters impact subjected to the changes of glacier and snow cover. The glacier flood and glacial lake outburst floods occurred mainly in the Karakoram Mountains, Kunlun Mountains and the western of the southern slope of the Tianshan Mountains in the Tarim River Basin. The snowmelt floods occurred mainly in Altay area, Tacheng area and the northern slope of the Tianshan Mountains in North Xinjiang. The glacier debris and the ice and snow avalanches disasters occurred mainly in the Pamirs Plateau, the western of the Tianshan Mountains, the Karakorum and the West Kunlun Mountains. The snowdrift occurred mainly in the middle and western of the Tianshan Mountains regions. With global warming, especially the beginning of the climate change from warm-dry to warm-wet in 1987 in Xinjiang, the glacier retreat intensified, the melt water increases, the glacier floods and debris flows increased with the increased of glacier melt water, and the snowmelt floods, ice and snow avalanches and snowdrift enhanced with the snow cover increased in winter and the air temperature rise, the alpine ice disintegration caused by ice avalanches with climate warming showed an increasing trend. The ice and snow disasters dominated by the glacier and snow floods in Xinjiang. The increasing trend of the frequency and intensity of glacier and snow floods under the influence of climate change have been observed in the last decade in the Xinjiang region. The water safety and disasters and other problems caused by glacial lake outburst floods and glacial floods in the Tarim Basin and the ice and snowmelt floods in spring in North Xinjiang have become increasingly prominent, and have great harm on the local lives, property and socio-economic development. With the glacier melt water increasing, some new disaster may be formed in the future. For the numerous glaciers, snow disaster induced by the climate change, there is a lack of adaptation on disaster monitoring, forecasting and early warning. So it should be keep an eye on the ice and snow disasters with the global climate change accelerating consistently, and to strengthen the study of the impact assessment and adaptation strategies of the disasters, and make the science and technology play a leading role in disaster reduction.
The existence, content and distribution of unfrozen water (liquid water) in glacier ice can exert an important influence on the physics and chemistry of glaciers. In this paper, we reported the discovery of the water-rich ice layers in Tibetan glaciers and its environmental significances. During the ice core drilling on the Yuzhufeng Glacier in the Kunlun Mountains in 2007, it was found that there was a water-rich ice layer at the depths from 34.34 to 34.64 m at the Core 1 site, and the water in this ice layer had a confined property and its confined water head was at least 8.54 m. The water-rich ice layer not only influences the glacier temperature field, and also makes the δ18O record homogeneous. The concentrations of ions in the water-rich ice layer were much higher than that in the ice layer above it. This was caused by the process of elution of ions in firn at the beginning of the formation of the water-rich ice layer. Through calculating, it was revealed that the sequence of preferential elution of ions in firn on the Yuzhufeng Glacier was NO3-> Mg2+> Na+> Cl- > K+> SO42> Ca2+> NH4+. Moreover, it was proposed that the ratio of the concentration of ion that was the most easily elution (NO3- for the Yuzhufeng Glacier) to that that was not the most easily elution (NH4+ for the Yuzhufeng Glacier) might be used for recognizing whether or not a peak value of ion in ice core was related to the processes of ion elution, and the higher the ratio was, the most possibly the peak value was related to ion elution. There were very close correlations between concentrations of Ca2+ and SO2-4 and electric conductivity in ice of the Yuzhufeng Glacier. Those imply that the influences of chemical composition of ice on its electric property should be considered when using electromagnetism method to estimate the water content in glacier ice. By comprehensive analysis of the water-rich ice layers appeared in other glaciers on the Tibetan Plateau, it could be concluded that the water-rich ice layers were just distributed as lentoid in glaciers, and their existences indicted that the climate was warm when they formed near surface of the accumulation zone. It was supposed that when a water-rich ice layer move down to the bed at lower part of glacier, the tongue of the glacier might break abruptly and slid downward to lower reaches owing to its large strain rate, and consequently hazards might occur.
Climatic change is focused intensely by worldwide scientists. However, it is not clear how climate changes at high elevation, particularly, on the Tibetan Plateau with an average altitude of more than 4 000 m. In this study, a comparison of δ18O values as temperature proxies from ice cores extracted from Guliya, Tanggula, Dasuopu and Ningjingangsang during the past 100 years is conducted. Meteorological records from Naryn and Northern Hemisphere for the same period are compared with the four ice cores records. The result shows that the Tibetan Plateau has experienced four cold periods during the 100 years: around 1910, around 1920, around 1950 and the 1970s. In addition, four warm periods had appeared after each cold event. Furthermore, the warming trend was getting stronger and stronger while the cooling trend was getting weaker and weaker. Spatially, the warming process in northern Tibetan Plateau was stronger than that in the southern Tibetan Plateau. Temporally, two cold periods around 1910 and around 1920 were recorded obviously, and the other two cold periods of around 1950 and the 1970s were inconspicuous. Although there was a short cooling event in the early 1990s, it was defined not as a cold period, but as a pause during a warming trend, followed by a continuous climate warming after that event.
The Ghulkin Glacier is one of the most typical active glaciers, which threats the Karakoram Highway (KKH) with its nearest snout position variation. The glacier fluctuation significantly influences the design and construction of the Improvement Project of KKH. In order to trace the movement history of the Ghulkin Glacier and understand its recent behavior, in this paper, literatures dated as old as from the past two hundred years were analyzed and then a consecutive three year field surveys had been made from 2008 to 2011. Distances from the south and north glacier tongues of the Ghulkin Glacier to the left bank of Hunza River in the period of 1885-1994 were sketched in this paper. The field survey of the snout position was made and compared with history records. It is found that the snout position had fluctuated by 625 m during the period of 1885-1980, with three retreats and three advances, respectively, and a notable advance from 1913 to 1925 and a small advance from 1966 to 1978; The debris flow gouge of K676+660 rises year after year and the channel of meltwater of south glacier tongue has changed from K676+660 to K676+450 since 2011; The south glacier tongue in 2010 retreated approximately 3 hundred meters as compared with that in 1994, and it retreated approximately 15 meters from 2010 to 2011. This research fills in the data gap of glacier along KKH in the latest thirty years. Glacial debris flow along KKH not only affected by regional climate, but also affected by glacier variation. Climate warming will lead to intense melting and retreat of glaciers, melting water mixing with moraine will induce large-scale glacial debris flow which poses a serious threat to KKH.
Snow over the Tibetan Plateau (TP) is an essential water source of major Asian rivers and greatly influences water availability in the downstream areas. The Nam Co basin is one of the most characteristic lake basins in TP, where the snow accumulation and its spatial pattern is an important indicator of the local climate and plays a crucial role in hydrological cycle. In this paper, the accuracies of two kinds of MODIS snow products were verified by in situ data, firstly. Furthermore, based on the MODIS data, the spatial changes of accumulation and ablation of snow cover, as well as snow cover days (SCD) and snow cover area (SCA), in Nam Co basin were analyzed. Combined the observed data with automatic weather data, the temporal variation of snow cover elements in Nam Co basin, such as snow depth (SD), snow water equivalent (SWE), snow density and SCD, were discussed. Finally, the relationships between snow cover elements and climate factors, such as temperature, precipitation and wind speed, were also discussed. The result shows: (1) the snow identification accuracy of MOD10A2 is higher than that of MOD10A1.However, its total identification accuracy is lower than that of MOD10A1; (2) there are spatial variations of accumulation and ablation of snow cover in Nam Co basin. The trend for the snow cover accumulation in the Nam Co basin is obviously clear, increasing from southeast to northwest of the basin, but the snow cover ablation has an opposite trend. Hence, the SCD in the south part of Nam Co basin is the maximum and that of the west part is the minimum; (3) the temporal variation of snow cover elements presents double peaks, generally in October and November or January. All kinds of snow cover elements are strongly influenced by temperature and precipitation from October to November, while from December to March, they are influenced by temperature. The average annual snow cover ratio is 21.9% of the total basin, with 50.6% in the east (due to the lake effect) and only 18.3% in other area of the basin. Lake effect has a distinct impact on the Nam Co basin, resulting in the mean SD and SWE all higher than those in the surrounding stations, such as Damxung, Nagchu and Baingoin.
A data set observed from 93 stations of Xinjiang Uygur Autonomous Region is used to analyze the spatial distribution and temporal change of the maximum depth of frozen soil. The results showed that: (1) Monthly maximum depth of frozen soil in Xinjiang has obvious seasonal variation, with the maximum in areas with lower altitude presented in January, but in areas with higher altitude presented in February; (2) the maximum depth of frozen soil in north of the region is higher than that in south of the region, and those in mountain areas are greater than those in plains; the distribution of maximum depth of frozen soil was similar to that of air temperature; the spatial correlation coefficients between the maximum depth of frozen soil and air temperature are-0.795, -0.736 and -0.848 for all year round, winter and spring, respectively; (3) There had a distinct decreasing during the 45 years in Xinjiang, with regression coefficients of areas with higher and lower altitude of -15.65 cm·(10a)-1 and -9.48 cm·(10a)-1, and their correlation coefficients with air temperature are -0.51 and -0.69, which had all past 0.001 significance level. Otherwise, the decreasing in winter shows that in Region a1 the decreasing was sharper than that in Region a2, but in spring, the decreasing in Region a2 was sharper than that in Region a1; (4) There was an abrupt change of the maximum depth of frozen soil during the 45 years in the autonomous region; the years of mutation in the areas with higher altitude and lower altitude were 1996/1997 and 1978/1979, respectively, which can also prove that impact from air temperature in areas with higher altitude was latter than that in areas with lower altitude. The reductions of yearly maximum depth of frozen soil in areas with higher altitude and lower altitude were 61.12 cm and 26.67 cm, respectively.
Based on daily mean air temperature and frozen soil depth data of 96 meteorological stations in Xinjiang from 1961 to 2010, the fundamental spatial-temporal change characteristics of cumulated negative temperature and maximum frozen soil depth and the relationship between them were analyzed by using the methods of linear regression, Mann-Kendall test and mixed spatial interpolation technology based on ArcGIS. The main results are as the follows: In the 50 years from 1961 to 2010, the cumulated negative temperature had significantly decreased, with the rate of 51.5 ℃·d · (10a)-1, and had a significantly abrupt decreasing in 1985. Affected by this, the maximum frozen soil depth had significantly decreased, with the rate of -3.5 cm·d · (10a)-1, and had a significantly abrupt decreasing in 1988. When cumulated negative temperature decreases 100 ℃·d, the maximum frozen soil depth will decrease 4.6 cm. The decreasing range of maximum frozen soil depth in South Xinjiang is larger than that in North Xinjiang and Tianshan Mountains. Similar to the cumulated negative temperature in winter, maximum frozen soil depth decrease rate and decrease range before and after the mutations in North Xinjiang and Tianshan Mountains were larger than those in South Xinjiang.
The glacier melt water in the northern slopes of the Lenglongling Mountain, located in the East Qilian Mountains, is the main water supply to the Hexi Corridor. However, there is little observation data about the modern glaciers' surface flow velocities in this area. So, the Ningchanhe No.1 (NC No.1) Glacier and the Shuiguanhe No.4 (SG No.4) Glacier surface flow velocities were investigated by surveying stakes on the glacier surfaces. The annual mean surface flow velocity of the SG No.4 Glacier (5.2 m·a-1) was higher than that of the NC No.1 Glacier (2.8 m·a-1) during 2010-2012, due to the glacierized area of the former lager than that of the later. The maximum surface flow velocity of the SG No.4 Glacier appeared at the higher elevation of the observed area (close to the equilibrium line altitude), while the maximum velocity of the NC No.1 Glacier presented in the region with steeper slope. This shows that the maximum velocity of the glaciers commonly appears in the region close to the equilibrium line altitude; however, some topographic factors, such as slope etc., should be taken into consideration. Compared with the historical data, it is found that there is decreasing tendency of the annual mean surface flow velocity on the SG No.4 Glacier, which may be attributed to the glacier thinning as a result of continuous loss of mass.
Vulnerability of frozen ground is the vulnerability of frozen ground to climate change. The frozen ground system is susceptible to adverse effects of climate change, especially temperature variation. Study of the frozen ground vulnerability is the basic for improving the understanding of the vulnerabilities of the natural ecological, engineering, and ecological social economic systems to the impacts of frozen ground change, scientifically adapting to these effects. A frozen ground numerical model is developed using spatial principle component analysis supported by remote sensing and geographical information system technologies. The model contains nine factors describing topography, climate and frozen ground characteristics. The vulnerability of frozen ground to climate change is evaluated for the period of 1961-2007 on a regional scale. The vulnerability is graded into five levels: potential, light, medial, heavy and very heavy, following Natural Breaks Classification. The spatial distribution of frozen ground vulnerability is analyzed and the factors influencing the vulnerability are discussed. The results show that overall vulnerability of frozen ground in China is at medial level. However, the permafrost on the Tibetan Plateau is very vulnerable, at heavy and very heavy vulnerable level. Compared with seasonal frozen ground, permafrost to climate change is more vulnerable. Under the conditions of current temperature rise, the frozen ground vulnerability is mainly explained by topographical exposure and adaptive capacity of frozen ground to climate change.
Using conventional observation and automatic weather station data, the snowstorm weather process in November 3-5, 2012, in Xilingol League was diagnostically analyzed. It is found that the snowstorm is confined by a stable planetary scale weather system, and controlled by the low level shear line together with Hetao cyclone. The storm was a strong cold air in Mongolia trough (vortex) in high humidity and water vapor flux convergence region. Surface cyclone and North China Ridge had a decisive action to the snowstorm. Dynamic condition of the snowstorm had some different from synoptic model of heavy snow weather or blizzard weather in Inner Mongolia. One can see that there was no upper level jet stream. A low level jet with strong water vapor convergence and unstable energy condition provided beneficial condition to the snowstorm. The high-and low-level jets coupling was not obvious, but from the physical quantity analysis of vorticity and divergence in Xilingol League, it is found that there was strong ascending motion of upper air divergence with low-level convergence, which provided dynamic condition favorable to the snowstorm.
The impact of East Asian winter monsoon on winter precipitation in Northeast China is compared and analyzed in this paper. The winter precipitation data of Northeast China (including those in Heilongjiang, Jilin, Liaoning and east of Inner Mongolia) are used to analyze the spatial and temporal distributions of winter precipitation and winter precipitation days during 1961-2011. It is found that the spatial distribution of snowfall and snowfall days in Northeast China have obvious differences, low in southeast of Inner Mongolia, northwest of Liaoning, west of Jinlin and southwest of Heilongjiang, and high in east of Liaoning, south of Jilin, east of Heilongjiang, north of Heilongjiang and northeast of Inner Mongolia. The winter precipitation has a linear increasing trend, and the high and low values of winter precipitation have increased after the mid-1980s obviously. The analysis of East Asian winter monsoon index shows that the linear trend of East Asia winter monsoon has been weak after the mid-1980s; there is a negative correlation between the winter precipitation and East Asian winter monsoon in most regions of Northeast China.
Field observation was made around the Ngoring Lake in source regions of Yellow River during the period from June to July, 2010. The variations of radiation components, surface energy components, soil temperature and surface albedo under different weather conditions were analyzed in this paper. The results show that there are great differences of radiation and surface energy components variations between various weather conditions. The value of surface albedo decreases in sequence of sunny, overcast and rainy day. The averaged value of albedo during the observation period is about 0.21. The contribution to the radiation follows the order: upward longwave > downward longwave > downward shortwave and upward shortwave radiation. Their averaged daily integral value is 31.4 MJ·m-2, 25.6 MJ·m-2, 22.4 MJ·m-2 and 4.2 MJ·m-2, respectively. The net radiation is 12.5 MJ·m-2, which is accounting for about 55.7% of the shortwave radiation. The average daily integral values of the sensible heat, latent heat and 0-cm soil heat fluxes make up 21.2%, 43.1% and 8.2% of net radiation fluxes. Variation range of soil temperature decreases with depth. The averaged peak value of upper layer soil temperature is about 2 ℃ lower than that in sunny day, but there are no remarkable differences at deeper soil layers. The cloud and precipitation has large disturbance, resulting in the downward shortwave radiation weaken, the peak value of averaged sensible heat fluxes and 0-cm soil heat fluxes smaller than that in the sunny days, and the peak value of the averaged latent heat flux greater than that in sunny day. Because of huge thermal capacity of water and the water supply, the diurnal range of temperature is small around the lake, the change of surface temperature is also smaller, and the land surface temperature rises slowly too. So the latent heat flux is dominant component in the process of surface energy balance, the sensible heat flux take second place, and ground heat flux take third place. This study is helpful for understanding the water energy cycle under the background of climate change over the Yellow River basin, and will promote the rational use of solar resources and provide data support to the sustainable development of animal husbandry.
All rivers in the Hexi Corridor of Gansu Province originate from the north slopes of the Qilian Mountains and respectively belong to three large river systems, which are the Shiyang River, the Heihe River and the Shule River from east to west. The rivers are supplied by precipitation and snow and ice meltwater from the Qilian Mounta-ins. Therefore, the changes in precipitation and temperature in the upriver watershed of the rivers have quite pronounced effect on the change in mountain runoff and reasonable utilization of water resources in the Hexi Corridor. For this reason, the Qilian Mountains, together with the upstream watershed and runoff forming areas, are chosen as a study area, where the change characteristics and variation trend of precipitation under global warming backdrop are analyzed based on the observed data in the area. The results show that precipitations in the upper reaches of Heihe River and Shule River located in the middle and western Qilian Mountains have increased, but the annual and seasonal precipitations decreased in the 1960s, which means, as a whole, the climate in the upper reaches of the three river systems has shifted to wet in the past about 60 years.
Carbonate mineral and sulfate mineral composition changes during the Holocene in Huahai Lake were reconstructed using X-ray diffraction, and the K/Na change was reconstructed using X-ray fluorescence. Then, the lake water salinity change was reconstructed during 10.47-5.5 cal ka BP in Huahai Lake. The results showed that carbonate mineral was the main mineral deposition in the lake sediments during the early (10.47-8.87 cal ka BP) and middle Holocene (8.87 - 5.5 cal ka BP), except for some particular layers. In addition, K/Na ratio was higher in the early Holocene which indicated that lake water salinity in 10.47-8.87 cal ka BP was higher than that in 8.87-5.5 cal ka BP. It suggested that the water salinity change was consistent with lake level and effective humidity change during the early and middle Holocene, and the water salinity indicated the change in effective precipitation. In addition, combined with the lake dried up, which indicated that the climate became arid during the late Holocene, one can see that Holocene environmental change in Huahai Lake as follows: climate shifted from arid to humid in the early Holocene, and was most humid in the mid-Holocene and arid in the late Holocene. This pattern is different from Asian monsoon areas and westerly areas, showing that the monsoon-westerly transition zone is not only controlled by the Asian monsoon but also affected by westerly winds.
Dynamic response of embankment to train load in permafrost regions is a complicated interaction course between heat and force, and is also an engineering problem which is badly in need of solving. Using fundamental principles of physics of frozen soil, mechanics of frozen soil, heat transfer, a dynamic analysis model for embankment in permafrost regions is developed. Then, taking a typical section of the Qinghai-Tibet Railway as an example, dynamic response of embankment to train load is simulated, and dynamic stress, acceleration and displacement in the embankment are analyzed in detail. The following conclusions are drawn: (1) according to the calculation result of temperature field, a block of high temperature frozen soil takes place inside the embankment and its foundation, where mechanical property of the frozen soil becomes unstable after construction of embankment; (2) vertical acceleration takes place inside the embankment due to train load, and fluctuation range of the acceleration decreases with depth; fluctuation range of the center point of the top embankment surface is larger than that of the center point of the embankment bottom with an order of magnitude; (3)under train load, embankment displacement gradually decreases from ballast center to inside with an arc shape, and the displacement distribution has a symmetry form to the embankment midline; (4)seasonal difference of dynamic stresses is small on the embankment surface, but it is 7.5 kPa on the embankment bottom; (5) the attenuation curve of dynamic stress is different among different seasons, and the differences of the curves are small at the depth less than 2 m or more than 15 m below the embankment surface, but they are large in the depth range from 2 to 15 m below the embankment surface.
To construct expressway in western China is growing day by day. Some ways would be through cold regions unavoidably. Because road surface of the expressway has heat absorption area larger than that of normal highway, it is harder to make sure the stability of embankment in cold regions. Generally, it is necessary to take numerical analysis for the stability of embankment in cold regions. However, the conventional finite element methods for stability analysis always make deterministic analysis, which do not take random factors into account, such as material parameters and boundary conditions. Consequently, the results are deterministic under this circumstance and cannot understand how much effect on stability of embankment with random factors. In this paper, using stochastic finite element methods, considering the parameters of boundary conditions as random variables, the random temperature fields for expressway with wide embankment are obtained and analyzed. The analyzed results indicate that the effect of heat accumulation in wide embankment central is obvious, and the temperature variance is increasing towards the upper boundary of the embankment. The above mentioned effects increase with time.
Frost heave and thaw settlement have significant implications on construction and the safety operation of projects in cold regions, and thus are the urgent important issues to be solved for researchers. Soils subjected to freezing or thawing would cause various phenomena such as water migration, unfrozen water, consolidation and frozen fringe. These phenomena are closely related to their thermodynamics processes involving the mechanism of phase change of water and ice, ice segregation and water migration. However, the mechanism study has currently become a significant challenge. The freeze-thaw process is a complex thermo-hydro-mechanical coupling process in a thermodynamic framework. Numerical simulation of the process is developing from thermo-hydro coupling to thermo-hydro-mechanical coupling, which involves the evolution and mutual relations between pore water pressure, ice pressure, effective stress and pore pressure. Therefore, measurements of the parameters of frozen fringe are the key of theoretical study and numerical simulation. In recent decades, with the developing in technology a variety of advanced instruments and probes have been designed and used to uncover the micro-structural characteristics and thermodynamics mechanism of soils during the laboratory or field experiments. Herein, a detailed review was given about the phenomena, mechanism, testing condition and relevant numerical models associated with the freezing and thawing processes in soils, which will be a favor to the further understanding and research.
Thermokarst lake is a typical landform in ice-rich permafrost regions. Thermokarst lake plays an essential role in permafrost distribution, frozen soil hydrology, ecological system and environment in permafrost regions and is a hot topic in recent decades. In this paper, the recent progress in the research on thermokarst lakes is reviewed from the following four aspects: (1) the evolution and morphologic change process of thermokarst lake and the reason of natural thermokarst lake's drainage; (2) the thermal regime and thermal erosion of thermokarst lakes and the influence of thermokarst lake on the permafrost; (3) the interaction between thermokarst lake and ecological system; (4) the emission of greenhouse gas related to thermokarst lake variation. Finally, the major problems in the recent researches are discussed. Based on this review, a prospect on potential research directions and new focuses are presented.
Study of the physical and mechanical properties of saline soil has practical significance for solving salt expansion and frost heave damage problems in engineering. In this paper, a general overview about new research progress is presented in mechanisms of salt expansion, water and salt transfer and influence of freeze-thaw cycles on mechanical properties of saline frozen soil at home and abroad. The main findings and the current problems about salinity frozen soil in these aspects have been summed up. Researching priorities of physical and mechanical properties of saline frozen soil under freeze-thaw cycles, for example, the water and salt transfer, mechanism of salt expansion and the structure of saline frozen soil, are put forward so as to have a better service for engineering construction. The feasible study directions in the future are proposed.
Alpine desert is the mainly runoff yield regions and headwater regions for most large river and inland river basins in China. However, due to lack of observation data and theoretical basis, there are few researches focusing on the hydrological process of alpine desert at home and abroad. In this paper, water cycle observation and experiment were done to analyze the hydrological characteristics in the alpine desert zone of Hulugou watershed in non-freezing period. Observations show that: (1) during the experimental period (2009.6.7-9.30), precipitation was 541.4 mm at the experimental site, pan evaporation was 256.9 mm, Micro-Lysimeter evaporation was 122.8 mm, mean evaporation was 1.1 mm·d-1; (2) based on the experimental observation, condensation water was relatively abundant in the alpine desert zone. Although condensation water do not directly involve in the hydrological cycle of mountain runoff generation and confluence process, it consumed energy, offset part of solar radiation, indirectly involved in the runoff generation and confluence process; (3) runoff depth of the small watershed was 461.2 mm. Using elevation precipitation gradient, it was obtained that the average precipitation of the alpine desert watershed was 639.1 mm, with a runoff coefficient of 0.72.
Measurement and estimation of soil water content and soil temperature are the foundation of research on water and heat transfer processes of frozen soil, which are the important base and core link of water cycle in cold regions. To study the heat and water transfer processes on various underlying surfaces in cold regions, four research sites, covered with (1) alpine grassland (38°16' N, 99°52' E, 2 980 m a.s.l., seasonally frozen soil), (2) alpine meadow (38°15' N, 99°52' E, 3 380 m a.s.l., seasonally frozen soil), (3) alpine swampy meadow (38°13' N, 99°53' E, 3 710 m a.s.l., permafrost) and (4) alpine clod desert (38°13' N, 99°53' E, 4 167 m a.s.l., permafrost), were chosen. Four automatic weather stations were installed in each research sites to collect meteorological data. With the observed meteorological data and measured soil and vegetation properties, SHAW and CoupModel were introduced to simulate the transfer processes of energy and water in the sites. A comparison between the calculated from SHAW and measured soil water content and soil temperature shows that the R2 value is 0.65 and 0.90, and the R2 value between calculated from CoupModel and measurement is 0.72 and 0.93. It is found that CoupModel is an 1-D SVATs model better than SHAW for various underlying surfaces in cold regions.
Four research sites covered with (1) alpine grassland (seasonally frozen soil), (2) alpine meadow (seasonally frozen soil), (3) alpine swampy meadow (permafrost) and (4) alpine clod desert (permafrost) were chosen to study the heat and water transfer processes of various underlying surfaces in cold regions. The simulations of transfer process of water and heat by CoupModel show that the water and heat transfer from deeper layer to the upper one when the soil is freezing. At the beginning, water in the deep layer moves upward to the freezing front and releases heat during the freezing process. While the soil layer is frozen, the water flow between the frozen layers become zero and is controlled by the vertical soil water potential during the thawing period. The soil heat flux increases sharply when water phase change takes place in soil with frozen/thaw process. The difference of soil water flow in various underlying surfaces presents when soil layer is freezing. In freezing time, the flow time and quantity of water transfer from deeper layer to upper one in alpine swampy meadow site is large because of largest soil water content; there are more water transfer processes in the alpine clod desert site, because the capillary action increases when the ice fill in the macro-pore. Vegetation, soil characteristics, soil liquid water content and frozen soil types are the influence factors of difference transfer of heat and water in different underlying surfaces.
The wavelet analysis method is adopted to analyze the multi-time scale characteristics of monthly mean air temperature (MMT), monthly precipitation (MP) and monthly mean runoff (MMR) in the upstream of the Ürümq River from 1958 to 2006. The results show that there are significant primary periods with 12-month scale of MMT, MP and MMR from 1958 to 2006, and the order of oscillation signals is MMT> MMR > MP. Furthermore, there are 66-month and 96-month secondary periods for MMT, 6-month, 30-month and 72-month secondary periods for MP, and 6-month, 24-month, 36-month and 72-month secondary periods for MMR. Moreover, cross-wavelet transformation shows that the correlations between MMR and MMT, MMR and MP are not only reflected in 12-month primary periods and 6-month secondary periods, but also in 34-month and 72-month secondary periods between MMR and MMT, and 24-month, 36-month and 72-month secondary periods between MMR and MP. It is found that there are positive correlation at 12-month scale period between MMR and MMT, non-significant correlation at 6-month scale period between MMR and MMT, and negative correlation at other scale periods between MMR and MMT. However, all scale periods between MMR and MP are of significantly positive correlation.
The Datong River basin is in the water resources forming region in the upper reaches of the Yellow River, where there are rich hydropower resources, good natural vegetation and biology, but the environment is very vulnerable owing to climate change and human activity. The hydropower and water resources development status of the basin is analyzed. It is believed that water quantity in the middle and lower reaches is decreasing caused by regional water use and inter-basin water diversion. Water environment capacity is reducing as well. Average discharge at Qingshizui, Tiantang, Liancheng (Ⅱ) hydrology stations decreases 0.6%-9.6%, 0.5%-3.8% and 1.7%-52.9% from March to November, respectively. Water use at the upper Tiantang station is less, but it becomes larger from Tiantang station to Liancheng station, with an average runoff flow reducing of 5.7% in 1994-2010 as compared with that in 1977-1993. To 2011, 34 cascade hydropower stations have been built, of which there are 30 of diversion type and 4 of gate dam type. With less capacity and no storage capacity, in flood period hydropower stations drain water at the same time, which will enlarge river discharge instantly; in low-water period, storage and diversion will reduce the discharge of water, greatly affecting river flow. For disordered storage and drainage of cascade hydropower stations, the flood process changes from natural steady status to artificial intervention status, and the flood peak in upper reaches and lower reaches is inconsistent, as a result, hydrological monitoring and flood forecasting are greatly troubled, which threaten flood control in downstream area. The submergence, discontinuous flow, shrinking of aquatic organisms and plants in both banks and heavier water environment pollution in the middle and lower reaches resulted from excessive hydropower and water resources development negatively impact environment. It is suggested to carry out integrated water resources management, unified control water discharge of cascade hydropower stations, reserve necessary ecological base flow, insure ecological water use, strengthen monitoring of river level, runoff, sediment, water environment and aquatic organisms, in order to provide policy decision basis for river basin flood control, water resources management and environment protection.
Research of solute transport modeling in groundwater is related to many practical problems, such as groundwater contaminant of pesticide and petroleum. As compared to relatively complete development of groundwater flow modeling, solute transport modeling within groundwater is more complicated and the study is inadequate. In this paper, the mathematical model of the mechanism/process in groundwater solute transport is demonstrated; the applications of solute transport modelings in groundwater contaminant prevention, land salinization, seawater intrusion and petroleum and radioactive material diffuse-prevention are reviewed; the advection transport and advection-dispersion numerical methodology of solute transport modeling, their advantage/disadvantage and application examples are summarized. Finally, the insufficiency in current study is analyzed, and the breakthrough is expected of parameter determination, transport mechanism within fractured media and solute transport modeling within multi-media in the future.
The relationship between soil microbial quantity and soil property, variation characteristics of soil microbial quantity and soil microbial community structure in seven typical plots during freezing-thawing in Ebinur Lake area were studied. The results show that: (1)different types of soil microbial quantity are dependent on physico-chemical factors at different stages of freezing-thawing.In January, bacteria quantity and soil organic matter content are significant positive correlation (P<0.05), fungi quantity has extremely significant positive correlation with soil water content and soil organic matter content (P<0.01), also has significant positive correlation with soil total N and soil porosity (P<0.05); in March, only fungi quantity has extremely significant positive correlation with soil water content (P<0.01); in April, actinomycetes quantity has significant positive correlation with soil organic carbon and total N(P<0.05), but has significant negative correlation with soil pH value (P<0.05); (2) soil microbial quantity is lower during frozen period in the study area(92 275-367 250 CFU·g-1), and reaches a peak in the late freezing and thawing period (170 738-704 300 CFU·g-1 in April); 7-year abandoned land has the highest microbial quantity (434 625 CFU·g-1), while 3-year abandoned land has the lowest one (177 435 CFU·g-1); (3) in cold season, actinomycetes are dominant in the study area (81.9%); in thawing stage, bacterial is dominant (52.1%-53.9%). On the whole, soil microbial growth is limited by nitrogen source in this study area.
Based on the authorized projects of water resources allocation and the practices of the ecological water conveyance in the past 10 years, we discussed the relationship between ecological water conveyance and rational water resources allocation, and analyzed the key issues of ecological operation and the basic framework of ecological operation in the Tarim River basin. The environmental flows in Alar Station were calculated. We discussed the goals and measures of ecological operation in the Tarim River basin and suggest some regulations of ecological operation, such as combination of synchronous with concentration in the headstream, water consumption control by subsections in the Tarim River and underground water level regulation in lower reaches of the Tarim River. The regulations are expected to be useful in the integrated water resources management, the operations of the hydraulic engineering and the protection of ecological environment in the Tarim River basin.
There are 587 debris flow gullies have been investigated in 20 counties, districts and cities in Hexi Corridor area in Gansu Province by debris flow gully judgment standards, four characteristics of catchment area, loose material reserves, slope gradient and main gully longitudinal slope, taken as the measure indexes. The statistics from the field work and information analyses have shown that debris flow gullies in Hexi area mainly developed in the corridor of the fore range of southern and northern hilly areas, and they have a sparse distribution density and belong to sparse debris flow areas; geological disasters caused by debris flow in this area on the whole have a low and middle-level tendency of occurrence based on the results of susceptibility evaluation of debris flow gullies. The results also indicate that heavy rain occurring frequency in the research area showed a trend of increase under the influences of global warming. Therefore, it is suggested that studies be actively carried out on the debris flow development trend in Hexi area and on the correlativity between vegetation and occurrence susceptibility of debris flow in arid and semi-arid areas.
