Yichi Zhang - Academia.edu (original) (raw)
Papers by Yichi Zhang
Environmental Earth Sciences, 2010
The impacts of environmental flow controls on the water table and chemistry of groundwater in the... more The impacts of environmental flow controls on the water table and chemistry of groundwater in the Ejina Delta, an arid inland river basin in northwest China, were investigated with field observations in 2001 and 2009. The results indicate that the shallow groundwater level rose by 0-2 m in the upper reaches of the east tributary of the Heihe River and in the areas of Saihantaolai-Dalaikubu during the period of environmental flow controls. The chemical constituents of the groundwater show a distinct spatial heterogeneity with the total dissolved solids (TDS) in the groundwater increasing from the periphery towards the depocenter of the Ejina Basin. In addition, the rate of groundwater cycling in the south of the Ejina Delta increased, and the mineralization of groundwater declined, while the overall mineralization and salinity increased in the northern regions, especially in the depocenter of the Ejina Basin. Since shallow groundwater is important to the ecology of arid regions, and because understanding the changes in the shallow groundwater environment (groundwater level and hydrochemistry) in response to environmental flow controls is essential for the sustainable improvement of the ecological environment, the results of this paper can be used as a reference for watershed water resources planning and management to help maintain the health and proper function of rivers in arid regions.
Environmental Earth Sciences, 2014
Natural environment of mid-latitude deserts of Central Asia is undergoing rapid changes. One of i... more Natural environment of mid-latitude deserts of Central Asia is undergoing rapid changes. One of its elements is the relief. What needs to be particularly emphasized is its morphogenesis and landform evolution. In this study, a geomorphological research in the Ejina Basin (Inner Mongolia) is carried out with regard to identifying the main landforms and the contemporary geomorphic processes. We consider ancient and modern landforms as a unit and provide a general explanation for their evolution. Related environmental indications of existing landforms are discussed on the basis of climate geomorphology. Results show that the current basin is under the conditions favorable for the development and dominance of landforms originated from physical processes such as desiccationdeflation and aeolian. The landform system is characterized by its variable structure which is conditioned by specific hydrodynamics processes that existed during glaciations. It is suggested that landform patterns in Ejina are under the strong influence of rapid and/or intensive geomorphic processes. These signatures reflect the regional dynamics of landform evolution as characterized by a very effective integration of tectonic and climate-driven morphogenetic processes. Based on the present day climate data, we infer an obvious linkage of desert gorges and pediments in the basin to ancient humid phases, which provided high energy runoff for the formation of these landforms and were associated with erosional features under more humid and colder climate during the last glacial period. Desert plains and aeolian dunes in the central basin are the related products of contemporary climate. Clear evidences proving the landform inconsistency and landform instability in the Ejina are presented, indicating that the main geomorphic unit is experiencing transformation from alluvial plain to desert plain and then to aeolian dunes. However, the geomorphodiversity in the Ejina should be a compound result of complex surficial processes other than glaciation. Frost weathering, fluvial/alluvial action, desiccation-deflation and aeolian processes as well as climatic changes have played important roles.
Theoretical and Applied Climatology, 2011
Monthly observed wind speed data at 597 weather stations and NCEP wind speed data at 10 m above s... more Monthly observed wind speed data at 597 weather stations and NCEP wind speed data at 10 m above surface were used to explore the temporal variations of the wind speed for 1961-2007 in China. The results indicate that the temporal variation of annual wind speed in China has experienced four phases: two relatively steady periods from 1961 to 1968 and 1969 to 1974 with a sharp step change in 1969, a statistically significant decline stage from 1974 to 1990s, and another relatively steady period from 1990s to 2007. Except for the sharp step in 1969 being caused by the changes of observation instrument, other breakpoints correspond well with the positive and negative phases of the interdecadal Pacific oscillation. In addition, four different temporal variation patterns of annual wind speed in China have been identified by using cluster analysis and their spatial distributions were also explored.
Science in China Series D, 2006
The oasis expansion and economic development of the Manas River Valley is one of the most success... more The oasis expansion and economic development of the Manas River Valley is one of the most successful examples in Xinjiang. In this paper, the oasis spatial distribution pattern and dynamic change were examined using imageries of Landsat MSS, TM and ETM, land use and topographic maps in six different periods (such as 1949, 1962, 1976, 1989, 1999 and 2001) over the last 50 years in the valley. The oasis expansion process could be divided into two stages according to the annual rate of oasis area increase, the fast oasization stage (from 1949 to 1976) when the oasis area expanded from 156.385 km 2 in 1949 to 3,639.491 km 2 in 1976 because of rapidly increased population and quickly enlarged farmland area; and the urbanization stage (from 1976 to 2001) when the expansion ratio of farmland slowed down, and the urbanization process quickened, the total oasis area reached 5042.440 km 2 in 2001. With the continuous expansion of oasis and farmland, a large quantity of river water was drawn into irrigation ditch and plain lakes, so only a small quantity of river water could flow into lakes, as a result, the Manas Lake dried up, salization and basification problems happened in the low-lying oasis region. The natural swamp around the lake was shrunk greatly and biodiversity decreased significantly. The driving force analysis reveals that human activities, such as reclamation and population growth, played a major role in the oasis expansion and ecological deterioration in the Manas River Valley. So further efforts should be made to improve the efficiency of water resource utility and adjust layout of the regional agricultural and animal husbandry to keep the sustainable development of oasis economic belt of the northern slope of Tianshan Mts.
Science in China Series D: Earth Sciences, 2007
The Aksu River (the international river between China and Kirghiz) has become the main water sour... more The Aksu River (the international river between China and Kirghiz) has become the main water source for the Tarim River. It significantly influences the Tarim River’s formation, development and evolution. Along with the western region development strategy and the Tarim River basin comprehensive development and implementation, the research is now focused on the Aksu River basin hydrologic characteristic and hydrologic
Science in China Series D: Earth Sciences, 2007
Alpine snowmelt is an important generation mode for runoff in the source region of the Tarim Rive... more Alpine snowmelt is an important generation mode for runoff in the source region of the Tarim River basin, which covers four subbasins characterized by large area, sparse gauge stations, mixed runoff supplied by snowmelt and rainfall, and remarkably spatially heterogeneous precipitation. Taking the Kaidu River basin as a research area, this study analyzes the influence of these characteristics on the variables and parameters of the Snow Runoff Model and discusses the corresponding determination strategy to improve the accuracy of snowmelt simulation and forecast. The results show that: (i) The temperature controls the overall tendency of simulated runoff and is dominant to simulation accuracy, as the measured daily mean temperature cannot represent the average level of the same elevation in the basin and that directly inputting it to model leads to inaccurate simulations. Based on the analysis of remote sensing snow maps and simulation results, it is reasonable to approximate the mean temperature with 0.5 time daily maximum temperature. (ii) For the conflict between the limited gauge station and remarkably spatial heterogeneity of rainfall, it is not realistic to compute rainfall for each elevation zone. After the measured rainfall is multiplied by a proper coefficient and adjusted with runoff coefficient for rainfall, the measured rainfall data can satisfy the model demands. (iii) Adjusting time lag according to the variation of snowmelt and rainfall position can improve the simulation precision of the flood peak process. (iv) Along with temperature, the rainfall increases but cannot be completely monitored by limited gauge stations, which results in precision deterioration.
Journal of Hydrology, 2013
Groundwater plays a dominant role in the eco-environmental protection of arid/semi-arid areas. Un... more Groundwater plays a dominant role in the eco-environmental protection of arid/semi-arid areas. Understanding sources and mechanisms of groundwater recharge in the Ejina Basin, an arid inland river basin in northwest China, is important for water resource planning in this ecologically sensitive area. In this study, 90 water samples were collected from rainfall, rivers and lakes, and springs and pumping wells in 2009. Analysis of the aquifer system and hydrological conditions, together with hydrogeochemical and isotope techniques were used to investigate groundwater sources and their associated recharge processes. Our results show that shallow phreatic and deep confined groundwater differ greatly in their compositions, with a distinct spatial heterogeneity of phreatic groundwater TDS (from 365 mg/L to 5833 mg/ L), which increase along the shallow groundwater flow paths. Groundwater chemical evolution is mainly controlled by rock dominance and the evaporation-crystallization process, and the dominant anion species change systematically from HCO 3 to SO 4 to Cl, and the dissolved ions within the groundwater system from Na-and K-rich minerals and sulfate phases also contribute significantly to the groundwater composition. The stable isotope levels (d 18 O and d 2 H) of the surface water and the shallow phreatic groundwater confirm that the Heihe River and Badain Jaran Desert groundwater are the main sources recharging the phreatic aquifer in the Ejina Basin. Thus, river infiltration and desert front recharge should be considered as the two main recharge mechanisms of the Ejina aquifer. However, recharge from the Badain Jaran Desert aquifer to the Ejina Basin has occurred at a lower rate due to aridification since the middle Holocene. For this reason, the sustainable improvement of the ecological environment should be based on the shallow groundwater recharge of the phreatic aquifer in the Ejina Delta, which mainly takes place via seepage through the riverbed and direct infiltration during periods of environmental flow control.
Journal of Hydrology, 2013
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Journal of Hydrology, 2013
The spatial and temporal variability of the frequency of extreme precipitation events in China fo... more The spatial and temporal variability of the frequency of extreme precipitation events in China for 1961-2009 was examined using the high quality rainfall dataset provided by the China Meteorology Administration (CMA) for 599 stations. Extreme events were defined by duration and recurrence interval, the event durations chosen were 1, 5, 10 and 30 days and the event thresholds were those associated with recurrence intervals of 1, 5 and 10 years. The results indicated that temporal variations of extreme precipitation index (EPI) showed interannual and interdecadal variability. Time series of anomalies of the nine regional EPI indices indicated that Northeast China, North China and the Yellow River basin had experienced a decreasing trend of extreme rainfall events during the last 50 years, while other six regions, namely the Yangtze River basin, Southeast Coast, South China, the Inner Mongolia, Northwest China and Tibetan Plateau, had experienced an increasing trend of extreme rainfall events. Seasonal results indicated that 95.6% of 1-day, 1-yr recurrence interval extreme rainfall events occurred from April to September in China. The possible attributions of trend and variability of extreme rainfall events at China include, but are not limited to, El Niño -Southern Oscillation (ENSO), the magnitude of East Asian Monsoon, wind circulations, as well as global warming. Obviously these factors are not independent. For example, it has long been recognized that ENSO can exert an important impact on the East Asian monsoon.
Journal of Glaciology, 2006
Terminus fluctuation and area change in mountain glaciers in the Middle Chinese Tien Shan over th... more Terminus fluctuation and area change in mountain glaciers in the Middle Chinese Tien Shan over the past four decades are examined, based on Landsat multispectral scanner (MSS), Enhanced Thematic Mapper Plus (ETM+), Système Probatoire pour l'Observation de la Terre (SPOT) high resolution visible (HRV) imagery, topographical maps and China Glacier Inventory data using Geographical Information System (GIS) and remote-sensing techniques. This study shows that the glaciers in the study area have undergone continuous recession between 1963 and 2000.
Journal of Geographical Sciences, 2014
Based on the palaeoclimatic and palaeoenvironmental evidences of geological history and human his... more Based on the palaeoclimatic and palaeoenvironmental evidences of geological history and human history periods, this paper reviews the researches and progresses on the development of the sandy deserts in Xinjiang. It pointed out that the features of tectonic structure in Xinjiang had made both the Tarim Basin and the Junggar Basin being influenced greatly by the foehn effects originated from the planetary wind system of westerly, the East Asian ocean-continental monsoon and the topographical mountain-valley winds. The regional patterns of climate and environment since the Quaternary were characterized by the overall persistent drought accompanied by fluctuations in the secondary scale. Formations of aeolian sediments in the basins and at the margins are a potential response to global climate change, particularly the aridification of the Asian hinterland deduced by the uprising of the Tibetan Plateau and its surrounding highlands. For the question about the formation time of the Taklamakan Desert, because the research methods, objects and information carriers used in previous studies are different, there are many disputes in the academic circles at present. Evidences from aeolian deposits/rocks at the edge and in the hinterland of these sandy deserts and their chronological data indicate that an arid climate and land surface aeolian processes have occurred at the edge of the Tarim Basin and its hinterland areas since the Tertiary period. However, the duration time of these processes at mass scale should have begun after the middle Pleistocene and lasted to the Holocene. Occurrence of dune fields in recent 2000 years in the oasis areas should be greatly influenced by human factors.
Journal of Asian Earth Sciences, 2013
The forward model of mass budget Westerly climate Central Asia a b s t r a c t Chemical weatherin... more The forward model of mass budget Westerly climate Central Asia a b s t r a c t Chemical weathering is an integral part of the earth surface processes, whose spatial patterns and controlling factors on continental scale are still not fully understood. Highlands of the Asian continent have been shown having some of the highest observed rates of chemical weathering yet reported. However, the paucity of river gauge data in many of these terrains has limited determination of chemical weathering budget in a continental scale. A dataset of three large watersheds throughout northern Xinjiang in Central Asia is used to empirically identify chemical weathering regimes and interpret the underlying controlling factors. Detailed analysis of major ion ratios and a forward model of mass budget procedure are presented to distinguish the relative significances and contributions of silicate, carbonate weathering and evaporite dissolution. The analytical results show that carbonic acid is the most important weathering agent to the studied watersheds. Silicate weathering contributes, on average, $17.8% (molar basis) of total cations on a basin wide scale with an order of Zhungarer > Erlqis > Yili, indicating that silicate weathering, however, does not seem to be intense in the study basins. Evaporite dissolution, carbonate weathering and precipitation input contribute 43.6%, 29.7% and 8.9% of the total dissolved cations on average for the whole catchment, respectively. The three main morphological and hydrological units are reflected in water chemistry. Rivers from the montane areas (recharge area) of the three watersheds are very dilute, dominated by carbonate and silicate weathering, whereas the rivers of piedmont areas as well as the rivers of the sedimentary platform (runoff area) are dominated by carbonate weathering, and rivers of desert plain in the central Zhungarer basin (discharge area) are dominated by evaporite dissolution and are SO 4 rich. This spatial pattern indicates that, beside lithology, runoff conditions have significant role on the regional chemical weathering regimes. Chemical weathering processes in the areas appear to be significantly climate controlled, displaying a tight correlation with runoff and aridity. Carbonate weathering are mostly influenced by runoff, which is higher in the mountainous part of the studied basins. The identification of chemical weathering regimes from our study confirmed the weathering potential and complexity of temperate watersheds in arid environment and that additional studies of these terrains are warranted. However, because the dominant weathering reactions in the sedimentary platform of northern Xinjiang are of carbonates and evaporites rather than silicate minerals, and the climatic factors have important role on the rock weathering regimes, we think that weathering at the arid temperate drainage system (Central Asia) is maybe not an important long-term sink for atmospheric CO 2 , if the future climate has no great change.
Hydrological Processes, 2008
Snow cover depletion curves are required for several water management applications of snow hydrol... more Snow cover depletion curves are required for several water management applications of snow hydrology and are often difficult to obtain automatically using optical remote sensing data owing to both frequent cloud cover and temporary snow cover. This study develops a methodology to produce accurate snow cover depletion curves automatically using high temporal resolution optical remote sensing data (e.g. Terra Moderate
Hydrological Processes, 2011
The Ejina basin, which is located in arid and semi-arid areas of northwest China, has experienced... more The Ejina basin, which is located in arid and semi-arid areas of northwest China, has experienced severe environmental deterioration in the past several decades, and an exploratory project was launched by the Chinese Government in 2001 to restore this degraded ecosystem. In this study, multi-scale remotely sensed data and field investigations were used to quantify the responses of vegetation to the implementation of integrated water management under this project. In terms of the seasonal accumulated Normalized Difference Vegetation Index (SAN) variation, (1) the vegetation in 80Ð4% of the oasis regions showed an increasing or recovering trend, and increasing SAN trends with a magnitude greater than 0Ð14 a 1 mainly resulted from cultivated land reclamation; (2) the vegetation in 91Ð5% of the desert regions presented an increasing trend, and the statistically significant trends mainly appeared in the middle and lower Ejina basin; (3) the vegetation in 19Ð6% of oasis and 5Ð1% of desert regions showed a decreasing or degrading trend, mainly where rivers diminished and along artificial concrete canals; and (4) opposite signs of vegetation trends occurred simultaneously along some natural rivers experiencing water reduction, with a decreasing trend generally appearing in the high SAN regions, whereas an increasing trend was seen in the low SAN regions. The broad vegetation recovery observed was due to the comprehensive improvement of the water environment, which was attributed to both the increase in runoff entering the Ejina basin and the adoption of engineering measures. Vegetation degradation in the area mainly resulted from deterioration of the local water environment, which was closely related to the problems of water management. The results of this study can be used as a reference for adjusting the current water resource management strategy to effectively restore this ecosystem.
Ecohydrology, 2012
Groundwater-dependent vegetation (GDV) must have access to groundwater to maintain their growth a... more Groundwater-dependent vegetation (GDV) must have access to groundwater to maintain their growth and function. GDV distribution patterns are an important issue in arid vegetation ecology. Using groundwater attributes to explore the distribution patterns of GDV have been very limited. In this article, we selected the Ejina Desert Oasis as an area to investigate GDV and groundwater attributes. Twenty plant species and 31 plant plots of data were collected. Two-way indicator species analysis (TWINSPAN) was performed to determine GDV types. Detrended correspondence analysis (DCA) and detrended canonical correspondence analysis (DCCA) were performed to analyse the relationships between GDV and groundwater attributes. The results indicated that (1) six plant community types were classified by TWINSPAN; (2) DCA ordination analyses showed that the groundwater depth (Dep) was the main factor restricting the distribution patterns of GDV, and the distribution of the dominant species and corresponding vegetation types had strong similarities; (3) in the DCCA diagram, the first axis represented variations of Dep, while the second axis was related to the pH values; (4) with increased Dep, the community types made the transition from I to VI; and (5) the DCCA diagram was similar to the DCA. However, the distribution patterns of GDV were more compact in the DCCA, while the DCA showed that each association group appeared within a limited range and had a clear border against other communities. This study shows that ordination methods can be used to explain the relationships between the distribution patterns of GDV and groundwater attributes.
Aims Since 2000, the environmental flow controls project has been implemented in the lower Heih... more Aims Since 2000, the environmental flow controls project has been implemented in the lower Heihe River Basin, a typical arid inland river basin in northwest China, to restore the deteriorated ecological environment in this region. The aim of this study was to explore the impacts of groundwater fluctuations on vegetation dynamics. Our results can be used as a reference for water resources planning and management to maintain proper environmental flows in arid areas.
Methods The location (by Global Positioning System) and depth of the monitoring wells, as well as groundwater table depth and salinity were measured in situ at each site from July to August 2009. Based on the measurements of the groundwater table depth and salinity following the implementation of environmental flow controls project (EFCP) in the lower Heihe River Basin, the groundwater fluctuations during the period from 2001 to 2009 were analyzed. Descriptive statistics and Pearson's correlation were used to analyze the relationship between vegetation changes and groundwater table fluctuations. Additionally, the spatial distributions of the groundwater table depth and salinity were interpolated using the simple kriging method. Trend analysis was applied to the time series of integrated Moderate Resolution Imaging Spectroradiometer normalized difference vegetation index data to identify interannual vegetation dynamics. The relationship between vegetation status and groundwater environment was investigated at different spatial scales by analyzing and comparing the time series and trends.
Important Findings (i) The groundwater table and salinity increased significantly in most of the study area with spatial heterogeneity. On average, the groundwater table rose ∼0.5 and 1.5 m in the upper and lower Ejina Basin, respectively, and the groundwater salinity increased across the study area by 0–4%. (ii) A notable correlation between the vegetation status and the groundwater table was revealed when the groundwater table depth fluctuated between 1.8 and 3.5 m, whereas the vegetation did not show an obvious response to groundwater table changes when the groundwater table depth was more than 5–6 m. (iii) Vegetation restoration mainly occurred in riparian areas within 500–1 000 m of from natural rivers, where the groundwater table depth varied from 2 to 4 m, and salinity was <5%, whereas vegetation degradation appeared at some locations where groundwater environment had deteriorated.
Environmental Earth Sciences, 2010
The impacts of environmental flow controls on the water table and chemistry of groundwater in the... more The impacts of environmental flow controls on the water table and chemistry of groundwater in the Ejina Delta, an arid inland river basin in northwest China, were investigated with field observations in 2001 and 2009. The results indicate that the shallow groundwater level rose by 0-2 m in the upper reaches of the east tributary of the Heihe River and in the areas of Saihantaolai-Dalaikubu during the period of environmental flow controls. The chemical constituents of the groundwater show a distinct spatial heterogeneity with the total dissolved solids (TDS) in the groundwater increasing from the periphery towards the depocenter of the Ejina Basin. In addition, the rate of groundwater cycling in the south of the Ejina Delta increased, and the mineralization of groundwater declined, while the overall mineralization and salinity increased in the northern regions, especially in the depocenter of the Ejina Basin. Since shallow groundwater is important to the ecology of arid regions, and because understanding the changes in the shallow groundwater environment (groundwater level and hydrochemistry) in response to environmental flow controls is essential for the sustainable improvement of the ecological environment, the results of this paper can be used as a reference for watershed water resources planning and management to help maintain the health and proper function of rivers in arid regions.
Environmental Earth Sciences, 2014
Natural environment of mid-latitude deserts of Central Asia is undergoing rapid changes. One of i... more Natural environment of mid-latitude deserts of Central Asia is undergoing rapid changes. One of its elements is the relief. What needs to be particularly emphasized is its morphogenesis and landform evolution. In this study, a geomorphological research in the Ejina Basin (Inner Mongolia) is carried out with regard to identifying the main landforms and the contemporary geomorphic processes. We consider ancient and modern landforms as a unit and provide a general explanation for their evolution. Related environmental indications of existing landforms are discussed on the basis of climate geomorphology. Results show that the current basin is under the conditions favorable for the development and dominance of landforms originated from physical processes such as desiccationdeflation and aeolian. The landform system is characterized by its variable structure which is conditioned by specific hydrodynamics processes that existed during glaciations. It is suggested that landform patterns in Ejina are under the strong influence of rapid and/or intensive geomorphic processes. These signatures reflect the regional dynamics of landform evolution as characterized by a very effective integration of tectonic and climate-driven morphogenetic processes. Based on the present day climate data, we infer an obvious linkage of desert gorges and pediments in the basin to ancient humid phases, which provided high energy runoff for the formation of these landforms and were associated with erosional features under more humid and colder climate during the last glacial period. Desert plains and aeolian dunes in the central basin are the related products of contemporary climate. Clear evidences proving the landform inconsistency and landform instability in the Ejina are presented, indicating that the main geomorphic unit is experiencing transformation from alluvial plain to desert plain and then to aeolian dunes. However, the geomorphodiversity in the Ejina should be a compound result of complex surficial processes other than glaciation. Frost weathering, fluvial/alluvial action, desiccation-deflation and aeolian processes as well as climatic changes have played important roles.
Theoretical and Applied Climatology, 2011
Monthly observed wind speed data at 597 weather stations and NCEP wind speed data at 10 m above s... more Monthly observed wind speed data at 597 weather stations and NCEP wind speed data at 10 m above surface were used to explore the temporal variations of the wind speed for 1961-2007 in China. The results indicate that the temporal variation of annual wind speed in China has experienced four phases: two relatively steady periods from 1961 to 1968 and 1969 to 1974 with a sharp step change in 1969, a statistically significant decline stage from 1974 to 1990s, and another relatively steady period from 1990s to 2007. Except for the sharp step in 1969 being caused by the changes of observation instrument, other breakpoints correspond well with the positive and negative phases of the interdecadal Pacific oscillation. In addition, four different temporal variation patterns of annual wind speed in China have been identified by using cluster analysis and their spatial distributions were also explored.
Science in China Series D, 2006
The oasis expansion and economic development of the Manas River Valley is one of the most success... more The oasis expansion and economic development of the Manas River Valley is one of the most successful examples in Xinjiang. In this paper, the oasis spatial distribution pattern and dynamic change were examined using imageries of Landsat MSS, TM and ETM, land use and topographic maps in six different periods (such as 1949, 1962, 1976, 1989, 1999 and 2001) over the last 50 years in the valley. The oasis expansion process could be divided into two stages according to the annual rate of oasis area increase, the fast oasization stage (from 1949 to 1976) when the oasis area expanded from 156.385 km 2 in 1949 to 3,639.491 km 2 in 1976 because of rapidly increased population and quickly enlarged farmland area; and the urbanization stage (from 1976 to 2001) when the expansion ratio of farmland slowed down, and the urbanization process quickened, the total oasis area reached 5042.440 km 2 in 2001. With the continuous expansion of oasis and farmland, a large quantity of river water was drawn into irrigation ditch and plain lakes, so only a small quantity of river water could flow into lakes, as a result, the Manas Lake dried up, salization and basification problems happened in the low-lying oasis region. The natural swamp around the lake was shrunk greatly and biodiversity decreased significantly. The driving force analysis reveals that human activities, such as reclamation and population growth, played a major role in the oasis expansion and ecological deterioration in the Manas River Valley. So further efforts should be made to improve the efficiency of water resource utility and adjust layout of the regional agricultural and animal husbandry to keep the sustainable development of oasis economic belt of the northern slope of Tianshan Mts.
Science in China Series D: Earth Sciences, 2007
The Aksu River (the international river between China and Kirghiz) has become the main water sour... more The Aksu River (the international river between China and Kirghiz) has become the main water source for the Tarim River. It significantly influences the Tarim River’s formation, development and evolution. Along with the western region development strategy and the Tarim River basin comprehensive development and implementation, the research is now focused on the Aksu River basin hydrologic characteristic and hydrologic
Science in China Series D: Earth Sciences, 2007
Alpine snowmelt is an important generation mode for runoff in the source region of the Tarim Rive... more Alpine snowmelt is an important generation mode for runoff in the source region of the Tarim River basin, which covers four subbasins characterized by large area, sparse gauge stations, mixed runoff supplied by snowmelt and rainfall, and remarkably spatially heterogeneous precipitation. Taking the Kaidu River basin as a research area, this study analyzes the influence of these characteristics on the variables and parameters of the Snow Runoff Model and discusses the corresponding determination strategy to improve the accuracy of snowmelt simulation and forecast. The results show that: (i) The temperature controls the overall tendency of simulated runoff and is dominant to simulation accuracy, as the measured daily mean temperature cannot represent the average level of the same elevation in the basin and that directly inputting it to model leads to inaccurate simulations. Based on the analysis of remote sensing snow maps and simulation results, it is reasonable to approximate the mean temperature with 0.5 time daily maximum temperature. (ii) For the conflict between the limited gauge station and remarkably spatial heterogeneity of rainfall, it is not realistic to compute rainfall for each elevation zone. After the measured rainfall is multiplied by a proper coefficient and adjusted with runoff coefficient for rainfall, the measured rainfall data can satisfy the model demands. (iii) Adjusting time lag according to the variation of snowmelt and rainfall position can improve the simulation precision of the flood peak process. (iv) Along with temperature, the rainfall increases but cannot be completely monitored by limited gauge stations, which results in precision deterioration.
Journal of Hydrology, 2013
Groundwater plays a dominant role in the eco-environmental protection of arid/semi-arid areas. Un... more Groundwater plays a dominant role in the eco-environmental protection of arid/semi-arid areas. Understanding sources and mechanisms of groundwater recharge in the Ejina Basin, an arid inland river basin in northwest China, is important for water resource planning in this ecologically sensitive area. In this study, 90 water samples were collected from rainfall, rivers and lakes, and springs and pumping wells in 2009. Analysis of the aquifer system and hydrological conditions, together with hydrogeochemical and isotope techniques were used to investigate groundwater sources and their associated recharge processes. Our results show that shallow phreatic and deep confined groundwater differ greatly in their compositions, with a distinct spatial heterogeneity of phreatic groundwater TDS (from 365 mg/L to 5833 mg/ L), which increase along the shallow groundwater flow paths. Groundwater chemical evolution is mainly controlled by rock dominance and the evaporation-crystallization process, and the dominant anion species change systematically from HCO 3 to SO 4 to Cl, and the dissolved ions within the groundwater system from Na-and K-rich minerals and sulfate phases also contribute significantly to the groundwater composition. The stable isotope levels (d 18 O and d 2 H) of the surface water and the shallow phreatic groundwater confirm that the Heihe River and Badain Jaran Desert groundwater are the main sources recharging the phreatic aquifer in the Ejina Basin. Thus, river infiltration and desert front recharge should be considered as the two main recharge mechanisms of the Ejina aquifer. However, recharge from the Badain Jaran Desert aquifer to the Ejina Basin has occurred at a lower rate due to aridification since the middle Holocene. For this reason, the sustainable improvement of the ecological environment should be based on the shallow groundwater recharge of the phreatic aquifer in the Ejina Delta, which mainly takes place via seepage through the riverbed and direct infiltration during periods of environmental flow control.
Journal of Hydrology, 2013
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Journal of Hydrology, 2013
The spatial and temporal variability of the frequency of extreme precipitation events in China fo... more The spatial and temporal variability of the frequency of extreme precipitation events in China for 1961-2009 was examined using the high quality rainfall dataset provided by the China Meteorology Administration (CMA) for 599 stations. Extreme events were defined by duration and recurrence interval, the event durations chosen were 1, 5, 10 and 30 days and the event thresholds were those associated with recurrence intervals of 1, 5 and 10 years. The results indicated that temporal variations of extreme precipitation index (EPI) showed interannual and interdecadal variability. Time series of anomalies of the nine regional EPI indices indicated that Northeast China, North China and the Yellow River basin had experienced a decreasing trend of extreme rainfall events during the last 50 years, while other six regions, namely the Yangtze River basin, Southeast Coast, South China, the Inner Mongolia, Northwest China and Tibetan Plateau, had experienced an increasing trend of extreme rainfall events. Seasonal results indicated that 95.6% of 1-day, 1-yr recurrence interval extreme rainfall events occurred from April to September in China. The possible attributions of trend and variability of extreme rainfall events at China include, but are not limited to, El Niño -Southern Oscillation (ENSO), the magnitude of East Asian Monsoon, wind circulations, as well as global warming. Obviously these factors are not independent. For example, it has long been recognized that ENSO can exert an important impact on the East Asian monsoon.
Journal of Glaciology, 2006
Terminus fluctuation and area change in mountain glaciers in the Middle Chinese Tien Shan over th... more Terminus fluctuation and area change in mountain glaciers in the Middle Chinese Tien Shan over the past four decades are examined, based on Landsat multispectral scanner (MSS), Enhanced Thematic Mapper Plus (ETM+), Système Probatoire pour l'Observation de la Terre (SPOT) high resolution visible (HRV) imagery, topographical maps and China Glacier Inventory data using Geographical Information System (GIS) and remote-sensing techniques. This study shows that the glaciers in the study area have undergone continuous recession between 1963 and 2000.
Journal of Geographical Sciences, 2014
Based on the palaeoclimatic and palaeoenvironmental evidences of geological history and human his... more Based on the palaeoclimatic and palaeoenvironmental evidences of geological history and human history periods, this paper reviews the researches and progresses on the development of the sandy deserts in Xinjiang. It pointed out that the features of tectonic structure in Xinjiang had made both the Tarim Basin and the Junggar Basin being influenced greatly by the foehn effects originated from the planetary wind system of westerly, the East Asian ocean-continental monsoon and the topographical mountain-valley winds. The regional patterns of climate and environment since the Quaternary were characterized by the overall persistent drought accompanied by fluctuations in the secondary scale. Formations of aeolian sediments in the basins and at the margins are a potential response to global climate change, particularly the aridification of the Asian hinterland deduced by the uprising of the Tibetan Plateau and its surrounding highlands. For the question about the formation time of the Taklamakan Desert, because the research methods, objects and information carriers used in previous studies are different, there are many disputes in the academic circles at present. Evidences from aeolian deposits/rocks at the edge and in the hinterland of these sandy deserts and their chronological data indicate that an arid climate and land surface aeolian processes have occurred at the edge of the Tarim Basin and its hinterland areas since the Tertiary period. However, the duration time of these processes at mass scale should have begun after the middle Pleistocene and lasted to the Holocene. Occurrence of dune fields in recent 2000 years in the oasis areas should be greatly influenced by human factors.
Journal of Asian Earth Sciences, 2013
The forward model of mass budget Westerly climate Central Asia a b s t r a c t Chemical weatherin... more The forward model of mass budget Westerly climate Central Asia a b s t r a c t Chemical weathering is an integral part of the earth surface processes, whose spatial patterns and controlling factors on continental scale are still not fully understood. Highlands of the Asian continent have been shown having some of the highest observed rates of chemical weathering yet reported. However, the paucity of river gauge data in many of these terrains has limited determination of chemical weathering budget in a continental scale. A dataset of three large watersheds throughout northern Xinjiang in Central Asia is used to empirically identify chemical weathering regimes and interpret the underlying controlling factors. Detailed analysis of major ion ratios and a forward model of mass budget procedure are presented to distinguish the relative significances and contributions of silicate, carbonate weathering and evaporite dissolution. The analytical results show that carbonic acid is the most important weathering agent to the studied watersheds. Silicate weathering contributes, on average, $17.8% (molar basis) of total cations on a basin wide scale with an order of Zhungarer > Erlqis > Yili, indicating that silicate weathering, however, does not seem to be intense in the study basins. Evaporite dissolution, carbonate weathering and precipitation input contribute 43.6%, 29.7% and 8.9% of the total dissolved cations on average for the whole catchment, respectively. The three main morphological and hydrological units are reflected in water chemistry. Rivers from the montane areas (recharge area) of the three watersheds are very dilute, dominated by carbonate and silicate weathering, whereas the rivers of piedmont areas as well as the rivers of the sedimentary platform (runoff area) are dominated by carbonate weathering, and rivers of desert plain in the central Zhungarer basin (discharge area) are dominated by evaporite dissolution and are SO 4 rich. This spatial pattern indicates that, beside lithology, runoff conditions have significant role on the regional chemical weathering regimes. Chemical weathering processes in the areas appear to be significantly climate controlled, displaying a tight correlation with runoff and aridity. Carbonate weathering are mostly influenced by runoff, which is higher in the mountainous part of the studied basins. The identification of chemical weathering regimes from our study confirmed the weathering potential and complexity of temperate watersheds in arid environment and that additional studies of these terrains are warranted. However, because the dominant weathering reactions in the sedimentary platform of northern Xinjiang are of carbonates and evaporites rather than silicate minerals, and the climatic factors have important role on the rock weathering regimes, we think that weathering at the arid temperate drainage system (Central Asia) is maybe not an important long-term sink for atmospheric CO 2 , if the future climate has no great change.
Hydrological Processes, 2008
Snow cover depletion curves are required for several water management applications of snow hydrol... more Snow cover depletion curves are required for several water management applications of snow hydrology and are often difficult to obtain automatically using optical remote sensing data owing to both frequent cloud cover and temporary snow cover. This study develops a methodology to produce accurate snow cover depletion curves automatically using high temporal resolution optical remote sensing data (e.g. Terra Moderate
Hydrological Processes, 2011
The Ejina basin, which is located in arid and semi-arid areas of northwest China, has experienced... more The Ejina basin, which is located in arid and semi-arid areas of northwest China, has experienced severe environmental deterioration in the past several decades, and an exploratory project was launched by the Chinese Government in 2001 to restore this degraded ecosystem. In this study, multi-scale remotely sensed data and field investigations were used to quantify the responses of vegetation to the implementation of integrated water management under this project. In terms of the seasonal accumulated Normalized Difference Vegetation Index (SAN) variation, (1) the vegetation in 80Ð4% of the oasis regions showed an increasing or recovering trend, and increasing SAN trends with a magnitude greater than 0Ð14 a 1 mainly resulted from cultivated land reclamation; (2) the vegetation in 91Ð5% of the desert regions presented an increasing trend, and the statistically significant trends mainly appeared in the middle and lower Ejina basin; (3) the vegetation in 19Ð6% of oasis and 5Ð1% of desert regions showed a decreasing or degrading trend, mainly where rivers diminished and along artificial concrete canals; and (4) opposite signs of vegetation trends occurred simultaneously along some natural rivers experiencing water reduction, with a decreasing trend generally appearing in the high SAN regions, whereas an increasing trend was seen in the low SAN regions. The broad vegetation recovery observed was due to the comprehensive improvement of the water environment, which was attributed to both the increase in runoff entering the Ejina basin and the adoption of engineering measures. Vegetation degradation in the area mainly resulted from deterioration of the local water environment, which was closely related to the problems of water management. The results of this study can be used as a reference for adjusting the current water resource management strategy to effectively restore this ecosystem.
Ecohydrology, 2012
Groundwater-dependent vegetation (GDV) must have access to groundwater to maintain their growth a... more Groundwater-dependent vegetation (GDV) must have access to groundwater to maintain their growth and function. GDV distribution patterns are an important issue in arid vegetation ecology. Using groundwater attributes to explore the distribution patterns of GDV have been very limited. In this article, we selected the Ejina Desert Oasis as an area to investigate GDV and groundwater attributes. Twenty plant species and 31 plant plots of data were collected. Two-way indicator species analysis (TWINSPAN) was performed to determine GDV types. Detrended correspondence analysis (DCA) and detrended canonical correspondence analysis (DCCA) were performed to analyse the relationships between GDV and groundwater attributes. The results indicated that (1) six plant community types were classified by TWINSPAN; (2) DCA ordination analyses showed that the groundwater depth (Dep) was the main factor restricting the distribution patterns of GDV, and the distribution of the dominant species and corresponding vegetation types had strong similarities; (3) in the DCCA diagram, the first axis represented variations of Dep, while the second axis was related to the pH values; (4) with increased Dep, the community types made the transition from I to VI; and (5) the DCCA diagram was similar to the DCA. However, the distribution patterns of GDV were more compact in the DCCA, while the DCA showed that each association group appeared within a limited range and had a clear border against other communities. This study shows that ordination methods can be used to explain the relationships between the distribution patterns of GDV and groundwater attributes.
Aims Since 2000, the environmental flow controls project has been implemented in the lower Heih... more Aims Since 2000, the environmental flow controls project has been implemented in the lower Heihe River Basin, a typical arid inland river basin in northwest China, to restore the deteriorated ecological environment in this region. The aim of this study was to explore the impacts of groundwater fluctuations on vegetation dynamics. Our results can be used as a reference for water resources planning and management to maintain proper environmental flows in arid areas.
Methods The location (by Global Positioning System) and depth of the monitoring wells, as well as groundwater table depth and salinity were measured in situ at each site from July to August 2009. Based on the measurements of the groundwater table depth and salinity following the implementation of environmental flow controls project (EFCP) in the lower Heihe River Basin, the groundwater fluctuations during the period from 2001 to 2009 were analyzed. Descriptive statistics and Pearson's correlation were used to analyze the relationship between vegetation changes and groundwater table fluctuations. Additionally, the spatial distributions of the groundwater table depth and salinity were interpolated using the simple kriging method. Trend analysis was applied to the time series of integrated Moderate Resolution Imaging Spectroradiometer normalized difference vegetation index data to identify interannual vegetation dynamics. The relationship between vegetation status and groundwater environment was investigated at different spatial scales by analyzing and comparing the time series and trends.
Important Findings (i) The groundwater table and salinity increased significantly in most of the study area with spatial heterogeneity. On average, the groundwater table rose ∼0.5 and 1.5 m in the upper and lower Ejina Basin, respectively, and the groundwater salinity increased across the study area by 0–4%. (ii) A notable correlation between the vegetation status and the groundwater table was revealed when the groundwater table depth fluctuated between 1.8 and 3.5 m, whereas the vegetation did not show an obvious response to groundwater table changes when the groundwater table depth was more than 5–6 m. (iii) Vegetation restoration mainly occurred in riparian areas within 500–1 000 m of from natural rivers, where the groundwater table depth varied from 2 to 4 m, and salinity was <5%, whereas vegetation degradation appeared at some locations where groundwater environment had deteriorated.