In recent decades, China has been experiencing rapid economic development, population growth and urbanization. These processes have stressed the shortages of water resources in China, especially in the arid re- gions ...In recent decades, China has been experiencing rapid economic development, population growth and urbanization. These processes have stressed the shortages of water resources in China, especially in the arid re- gions of northwestern China. In order to sustain the expanding cropland, people increased groundwater exploitation in these regions. The purpose of this study was to quantitatively analyze the changes in land use and water resources, and their relationship in the middle reaches of the Heihe River Basin, a typical inland river basin in northwest China. The data of land use change were interpreted using aerial photographs （1965） and Landsat TM images （1986 and 2007）. The data of irrigation water volume in the irrigation districts were spatialized in the middle reaches of the Heihe River Basin. The spatial variation of the groundwater depth was interpolated using the geo- statistical method. The results showed that the cultivated cropland area along oasis fringe increased by 15.38% and 43.60% during the periods 1965-1986 and 1986-2007, respectively. Surface water amount for irrigation had almost doubled from 1956 to 2010. The decrease of grassland area mainly occurred at the alluvial fan in front of the Qilian Mountains, with 36.47% during 1965-1986 and 38.56% during 1986-2007, respectively. The groundwater depth in front of the mountain constantly increased from 1986 to 2007. We found that the overuse of surface water and overexploitation of groundwater had direct consequences on the natural environments. We suggests that the efficiency of surface water resources use among different irrigation distdcts needs to be improved, which will significantly ease the conflicts between increasing water demand for irrigation and a shortage of water resources in the middle reaches of the Heihe River Basin.展开更多
The runoff generated from mountainous regions is recognized as the main water source for inland river basins in arid environments. Thus, the mechanisms by which catchments retain water in soils are to be understood. T...The runoff generated from mountainous regions is recognized as the main water source for inland river basins in arid environments. Thus, the mechanisms by which catchments retain water in soils are to be understood. The water storage capacity of soil depends on its depth and capacity to retain water under gravita- tional drainage and evapotranspiration. The latter can be studied through soil water retention curve （SWRC）, which is closely related to soil properties such as texture, bulk density, porosity, soil organic carbon conteMt, and so on. The present study represented SWRCs using HYDRUS-1D. In the present study, we measured pl^ysical and hydraulic properties of soil samples collected from Sabina przewalskii forest （south-facing slope with highest solar radiation）, shrubs （west-facing slope with medium radiation）, and Picea crassifolia forest （north-facing slope with lowest radiation）, and analyzed the differences in soil water storage capacity of these soil samples. Soil water content of those three vegetation covers were also measured to validate the soil water storage capacity and to analyze the relationship between soil organic matter content and soil water content. Statistical analysis showed that different vegetation covers could lead to different soil bulk densities and differences in soil water retention on the three slope aspects. Sand content, porosity, and organic carbon content of the P. crassifolia forest were rela- tively greater compared with those of the S. przewalskii forest and shrubs. However, silt content and soil bulk density were relatively smaller than those in the S. przewalskii forest and shrubs. In addition, there was a sig- nificant linear positive relationship between averaged soil water content and soil organic matter content （P〈0.0001）. However, this relationship is not significant in the P. crassifolia forest. As depicted in the SWRCs, the water storage capacity of the soil was 39.14% and 37.38% higher in the P. crassifolia forest than in the S. przewalskii展开更多
The spatial resolution of general circulation models （GCMs） is too coarse to represent regional climate variations at the regional, basin, and local scales required for many environmental modeling and impact assessm...The spatial resolution of general circulation models （GCMs） is too coarse to represent regional climate variations at the regional, basin, and local scales required for many environmental modeling and impact assessments. Weather research and forecasting model （WRF） is a nextgeneration, fully compressible, Euler non-hydrostatic mesoscale forecast model with a runtime hydrostatic option. This model is useful for downscaling weather and climate at the scales from one kilometer to thousands of kilometers, and is useful for deriving meteorological parameters required for hydrological simulation too. The objective of this paper is to validate WRF simulating 5 km/ 1 h air temperatures by daily observed data of China Meteorological Administration （CMA） stations, and by hourly in-situ data of the Watershed Allied Telemetry Experimental Research Project. The daily validation shows that the WRF simulation has good agreement with the observed data; the R2 between the WRF simulation and each station is more than 0.93; the absolute of meanbias error （MBE） for each station is less than 2℃; and the MBEs of Ejina, Mazongshan and Alxa stations are near zero, with R2 is more than 0.98, which can be taken as an unbiased estimation. The hourly validation shows that the WRF simulation can capture the basic trend of observed data, the MBE of each site is approximately 2℃, the R2 of each site is more than 0.80, with the highest at 0.95, and the computed and observed surface air temperature series show a significantly similar trend.展开更多
Modeling the hydrological processes at catchment scale requires a flexible distributed scheme to represent the catchment to- pography, river network and vegetation pattern. This study has developed a distributed schem...Modeling the hydrological processes at catchment scale requires a flexible distributed scheme to represent the catchment to- pography, river network and vegetation pattern. This study has developed a distributed scheme for eco-hydrological simulation in the upper Heihe River. Based on a 1 km x 1 km grid system, the study catchment is divided into 461 sub-catchments, whose main streams form the streamflow pathway. Furthermore, a 1 km grid is represented by a number of topographically similar ＂hillslope-valley＂ systems, and the hillslope is the basic unit of the eco-hydrological simulation. This model is tested with a simplified hydrological simulation focusing on soil-water dynamics and streamflow routing. Based on a 12-year simulation from 2001 to 2012, it is found that variability in hydrological behavior is closely associated with climatic and landscape condi- tions especially vegetation types. The subsurface and groundwater flows dominate the total river runoff. This implies that the soil freezing and thawing process would significantly influence the runoff generation in the upper Heihe basin. Furthermore, the runoff components and water balance characteristics vary among different vegetation types, showing the importance of coupling the vegetation pattern into catchment hydrological simulation. This paper also discusses the model improvement to be done in future study.展开更多
Relative roles of climate change and human activities in desertification are the hotspot of research on desertification dynamic and its driving mechanism.To overcome the shortcomings of existing studies,this paper sel...Relative roles of climate change and human activities in desertification are the hotspot of research on desertification dynamic and its driving mechanism.To overcome the shortcomings of existing studies,this paper selected net primary productivity （NPP） as an indicator to analyze desertification dynamic and its impact factors.In addition,the change trends of actual NPP,potential NPP and HNPP （human appropriation of NPP,the difference between potential NPP and actual NPP） were used to analyze the desertification dynamic and calculate the relative roles of climate change,human activities and a combination of the two factors in desertification.In this study,the Moderate Resolution Imaging Spectroradiometer （MODIS）-Normalised Difference Vegetation Index （NDVI） and meteorological data were utilized to drive the Carnegie-Ames-Stanford Approach （CASA） model to calculate the actual NPP from 2001 to 2010 in the Heihe River Basin.Potential NPP was estimated using the Thornthwaite Memorial model.Results showed that 61％ of the whole basin area underwent land degradation,of which 90.5％ was caused by human activities,8.6％ by climate change,and 0.9％ by a combination of the two factors.On the contrary,1.5％ of desertification reversion area was caused by human activities and 90.7％ by climate change,the rest 7.8％ by a combination of the two factors.Moreover,it was demonstrated that 95.9％ of the total actual NPP decrease was induced by human activities,while 69.3％ of the total actual NPP increase was caused by climate change.The results revealed that climate change dominated desertification reversion,while human activities dominated desertification expansion.Moreover,the relative roles of both climate change and human activities in desertification possessed great spatial heterogeneity.Additionally,ecological protection policies should be enhanced in the Heihe River Basin to prevent desertification expansion under the condition of climate change.展开更多
Climatic change has significant impacts on snow cover in mid-latitude mountainous re- gions, in the meantime, spatial and temporal changes of snow cover and snowmelt runoffs are con- sidered as sensitive indicators fo...Climatic change has significant impacts on snow cover in mid-latitude mountainous re- gions, in the meantime, spatial and temporal changes of snow cover and snowmelt runoffs are con- sidered as sensitive indicators for climatic change. In this study, the upper Heihe Watershed in the Qilian Mountains was selected as a typical area affected by snow cover and snowmelt runoffs in northwestern China. The changes in air temperatures, precipitation, snowfall and spring snowmelt runoffs were analyzed for the period from 1956 to 2001. The results indicate that climatic warming was apparent, particularly in January and February, but precipitation just fluctuated without a clear trend. The possible changes of snowmelt runoffs in the upper Heihe watershed in response to a warming of 4℃ were simulated using Snowmelt Runoff Model (SRM) based on the degree-day factor algorithm. The results of the simulation indicate that a forward shifting of snow melting season, an increase in water flows in earlier melting season, and a decline in flows in later melting season would occur under a 4℃ warming scenario.展开更多
The Heihe River Basin is located in the arid and semi-arid regions of Northwest China.Here,the terrestrial ecosystem is vulnerable,making it necessary to identify the factors that could affect the ecosystem.In this st...The Heihe River Basin is located in the arid and semi-arid regions of Northwest China.Here,the terrestrial ecosystem is vulnerable,making it necessary to identify the factors that could affect the ecosystem.In this study,MODIS-NDVI data with a 250-m resolution were used as a proxy for the terrestrial ecosystem.By combining these with environmental factors,we were able to explore the spatial features of NDVI and identify the factors influencing the NDVI distribution in the Heihe River Basin during the period of 2000–2016.A geographical detector(Geodetector) was employed to examine the spatial heterogeneity of the NDVI and to explore the factors that could potentially influence the NDVI distribution.The results indicate that:(1) the NDVI in the Heihe River Basin appeared high in the southeast while being low in the north,showing spatial heterogeneity with a q-statistic of 0.38.The spatial trend of the vegetation in the three sub-basins generally increased in the growing seasons from 2000 to 2016;(2) The results obtained by the Geodetector(as denoted by the q-statistic as well as the degree of spatial association between the NDVI and environmental factors) showed spatial heterogeneity in the associations between the NDVI and the environmental factors for the overall basin as well as the sub-basins.Precipitation was the dominant factor for the overall basin.In the upper basin,elevation was found to be the dominant factor.The dominant factor in the middle basin was precipitation,closely followed by the soil type.In the lower basin,the dominant factor was soil type with a lower q-statistic of 0.13,and the dominant interaction between the elevation and soil type was nonlinearly enhanced(q-statistic = 0.22).展开更多
High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, ...High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk（Tamarix ramosissima） is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian for展开更多
Based on the data for meteorology, hydrology, soil, planting, vegetation, and socio-economic development of the irrigation region in the middle reaches of the Heihe River basin, Northwest China, the model of balance o...Based on the data for meteorology, hydrology, soil, planting, vegetation, and socio-economic development of the irrigation region in the middle reaches of the Heihe River basin, Northwest China, the model of balance of water supply and demand in the region was established, and the security of water resource was assessed, from which the results that the effects of unified management of water resources in the Heihe River basin between Gansu Province and Inner Mongolia on regional hydrology are significant with a decrease in water supply diverted from Heihe River and an increase in groundwater extracted. In addition, it was found that the groundwater level has been steadily decreasing due to over pumping and decrease in recharges. In present year （2003）, the volume of potential groundwater in the irrigation districts is far small because of the groundwater overdraft; even in the particular regions, there is no availability of groundwater resources for use. By 2003, water supply is not sufficient to meet the water demand in the different irrigation districts, the sustainable development and utilization of water resources are not secured, and the water supply crisis occurs in Pingchuan irrigation district. Achieving water security for the sustainable development of society, agriculture, economy, industry, and livelihoods while maintaining or improving the abilities of the management and planning of water resources, determining of the reasonable percentage between water supply and groundwater utilization and water saving in agricultural irrigation are taken into account. If this does not occur, it is feared that the present performance of water development and planning may further aggravate the problem of scarcities of water resources and further damage the fragile ecological system.展开更多
Land use and cover change(LUCC) is an important indicator of the human-earth system under climate/environmental change,which also serves as a key impact factor of carbon balance,and a major source/sink of soil carbon ...Land use and cover change(LUCC) is an important indicator of the human-earth system under climate/environmental change,which also serves as a key impact factor of carbon balance,and a major source/sink of soil carbon cycles.The Heihe River Basin(HRB) is known as a typical ecologically fragile area in the arid/semi-arid regions of northwestern China,which makes it more sensitive to the LUCC.However,its sensitivity varies in a broad range of controlling factors,such as soil layers,LUCCs and calculation methods(e.g.the fixed depth method,FD,and the equivalent mass method,ESM).In this study,we performed a meta-analysis to assess the response of soil organic carbon(SOC) and total nitrogen(TN) storage to the LUCC as well as method bias based on 383 sets of SOC data and 148 sets of TN data from the HRB.We first evaluated the calculation methods and found that based on the FD method,the LUCC caused SOC and TN storage to decrease by 17.39% and 14.27%,respectively;while the losses estimated using the ESM method were 19.31% and 18.52%,respectively.The deviations between two methods were mainly due to the fact that the FD method ignores the heterogeneity of soil bulk density(BD),which may underestimate the results subsequently.We then analyzed the response of SOC and TN storage to various types of the LUCC.In particular,when woodland and grassland were converted into cultivated land or other land types,SOC and TN suffered from heavy losses,while other LUCCs had minor influences.Finally,we showed that increasing the depth of the soil layers would reduce the losses of SOC and TN storage.In summary,we identified a series of controlling factors(e.g.soil layer,the LUCC and calculation method) to evaluate the impact of the LUCC on SOC and TN storage in the HRB,which should be considered in future research.展开更多
The Heihe River Basin is the second largest inland river basin in Northwest China and it is also a hotspot in arid hydrology, water resources and other aspects of researches in cold regions. In addition, the Heihe Riv...The Heihe River Basin is the second largest inland river basin in Northwest China and it is also a hotspot in arid hydrology, water resources and other aspects of researches in cold regions. In addition, the Heihe River Basin has complete landscape, moderate watershed size, and typical social ecological environmental problems. So far, there has been no detailed assessment of glaciers change information of the whole river basin. 1：50,000 topographic map data, Landsat TM/ETM＋ remote sensing images and digital elevation model data were used in this research. Through integrated computer automatic interpretation and visual interpretation methods, the object-oriented image feature extraction method was applied to extract glacier outline information. Glaciers change data were derived from analysis, and the glacier variation and its response to climate change in the period 1956/1963–2007/ 2011 were also analyzed. The results show that：（1） In the period 1956/1963–2007/2011, the Heihe River Basin＇s glaciers had an evident retreat trend, the total area of glaciers decreased from 361.69 km2 to 231.17 km^2; shrinking at a rate of 36.08%, with average single glacier area decrease 0.14 km^2; the total number of the glaciers decreased from 967 to 800.（2） Glaciers in this basin are mainly distributed at elevations of 4300–4400 m, 4400–4500 m and 4500–4600 m; and there are significant regional differences in glaciers distribution and glaciers change.（3） Compared with other western mountain glaciers, glaciers retreat in the Heihe River Basin has a higher rate.（4） Analysis of the six meteorological stations＇ annual average temperature and precipitation data from 1960 to 2010 suggests that the mean annual temperature increased significantly and the annual precipitation also showed an increasing trend. It is concluded that glacier shrinkage is closely related with temperature rising, besides, glacier melting caused by rising temperatures greater than glacier mass supply by increased precipitation to展开更多
The research of coupling WRF （Weather Research and Forecasting Model） with a land surface model is enhanced to explore the interaction of the atmosphere and land surface; however, regional applicability of WRF model...The research of coupling WRF （Weather Research and Forecasting Model） with a land surface model is enhanced to explore the interaction of the atmosphere and land surface; however, regional applicability of WRF model is questioned. In order to do the validation of WRF model on simulating forcing data for the Heihe River Basin, daily meteorological observation data from 15 stations of CMA （China Meteorological Administration） and hourly meteorological observation data from seven sites of WATER （Watershed Airborne Telemetry Experimental Research） are used to compare with WRF simulations, with a time range of a whole year for 2008. Results show that the average MBE （Mean Bias Error） of daily 2-m surface temperature, surface pressure, 2-m relative humidity and 10-m wind speed were -0.19 ℃, -4.49 hPa, 4.08% and 0.92 m/s, the average RMSE （Root Mean Square Error） of them were 2.11 ℃, 5.37 hPa, 9.55% and 1.73 m/s, and the average R （correlation coefficient） of them were 0.99, 0.98, 0.80 and 0.55, respectively. The average MBE of hourly 2-m surface temperature, surface pressure, 2-m relative humidity, 10-m wind speed, downward shortwave radiation and downward longwave were-0.16 ℃,-6.62 hPa,-5.14%, 0.26 m/s, 33.0 W/m^2 and-6.44 W/m^2, the average RMSE of them were 2.62 ℃, 17.10 hPa, 20.71%, 2.46 m/s, 152.9 W/m^2 and 53.5 W/m^2, and the average R of them were 0.96, 0.97, 0.70, 0.26, 0.91 and 0.60, respectively. Thus, the following conclusions were obtained： （1） regardless of daily or hourly validation, WRF model simulations of 2-m surface temperature, surface pressure and relative humidity are more reliable, especially for 2-m surface air temperature and surface pressure, the values of MBE were small and R were more than 0.96; （2） the WRF simulating downward shortwave radiation was relatively good, the average R between WRF simulation and hourly observation data was above 0.9, and the average R of downward longwave radiation was 0.6; （3） both wind speed and rainfall simulated fr展开更多
The object of this paper is the different plant communities in the Ejina desert riparian forest. Groundwater depth, soil moisture, plant water potential, relative leaf moisture content and water use efficiency was mon...The object of this paper is the different plant communities in the Ejina desert riparian forest. Groundwater depth, soil moisture, plant water potential, relative leaf moisture content and water use efficiency was monitored, and the response of soil moisture and plant ecology to the groundwater depth and the water use efficiency of the different plant communities was analyzed. The results showed that：（1） Along with the groundwater depth increasing, predawn and midday water potential of the plants, with the exception of Reaumuria soongorica, did not decrease significantly, indicating that when the groundwater depth is less than 3 m, the plant communities in the range of 4 km from the river way did not suffer or slightly suffer from water stress;（2） The distribution of higher soil moisture content within 0–3 m soil layer is suitable with the plants’ root system, as indicated in the communities of coexisting overripe Populus euphratica or Taramrix chinensis, both of which can release excessive water into soil for shallow rooted shrubs or herbaceous plants when there is water shortage;（3） R. soongorica can absorb deep soil moisture through deep roots for their own survival;（4） The community consisting of Sophora alopecuroides, Karelinia caspica, T. chinensis, and overripe P. euphratica has the best species combination for restoring the damaged eco-environment in the lower reaches of Heihe River;（5） The order of plants’ relative leaf water contents is K. caspica ＆gt; S. alopecuroides ＆gt; young P. euphratica ＆gt; overripe P. euphratica ＆gt; mature P. euphratica = T. chinensis coexisting with other species ＆gt; single R. soongorica ＆gt; single T. chinensis and the order of WUE is single T. chinensis ＆gt; single R. soongorica ＆gt; T. chinensis living in symbiosis with other species ＆gt; S. alopecuroides = young P. euphratica ＆gt; mature P. euphratica ＆gt; overripe P. euphratica ＆gt; K. caspica. Therefore, with ample soil moisture, the plant community helps rapid growth展开更多
[Objective] The effect of climate change on wetland ecological environment in Heihe River basin was researched.[Method] Based on meteorological data from six meteorological stations in Heihe River basin from 1959 to 2...[Objective] The effect of climate change on wetland ecological environment in Heihe River basin was researched.[Method] Based on meteorological data from six meteorological stations in Heihe River basin from 1959 to 2009,the effect of climate change on wetland ecological environment in Heihe River basin in recent 51 years was studied by means of statistical method.[Result] Temperature and precipitation in Heihe River basin showed obvious increasing trend in recent 51 years,especially in recent 20 years;climate change made Heihe River basin more and more dry,specially in mountain area;wetland ecological environment closely related to climate responded to climate change,such as groundwater level rise,wetland area decrease,agriculture planting structure change,meteorological disaster increase,destroyed biodiversity and so on.[Conclusion] Our study had important significance for the protection and development of wetland resources.展开更多
基金supported by the Chinese Academy of Sciences Action Plan for West Development Program Project (KZCX2-XB3-15)the National Natural Science Foundation of China (91125023)Funds for the Central Universities in China (lzujbky-2011-131)
文摘In recent decades, China has been experiencing rapid economic development, population growth and urbanization. These processes have stressed the shortages of water resources in China, especially in the arid re- gions of northwestern China. In order to sustain the expanding cropland, people increased groundwater exploitation in these regions. The purpose of this study was to quantitatively analyze the changes in land use and water resources, and their relationship in the middle reaches of the Heihe River Basin, a typical inland river basin in northwest China. The data of land use change were interpreted using aerial photographs （1965） and Landsat TM images （1986 and 2007）. The data of irrigation water volume in the irrigation districts were spatialized in the middle reaches of the Heihe River Basin. The spatial variation of the groundwater depth was interpolated using the geo- statistical method. The results showed that the cultivated cropland area along oasis fringe increased by 15.38% and 43.60% during the periods 1965-1986 and 1986-2007, respectively. Surface water amount for irrigation had almost doubled from 1956 to 2010. The decrease of grassland area mainly occurred at the alluvial fan in front of the Qilian Mountains, with 36.47% during 1965-1986 and 38.56% during 1986-2007, respectively. The groundwater depth in front of the mountain constantly increased from 1986 to 2007. We found that the overuse of surface water and overexploitation of groundwater had direct consequences on the natural environments. We suggests that the efficiency of surface water resources use among different irrigation distdcts needs to be improved, which will significantly ease the conflicts between increasing water demand for irrigation and a shortage of water resources in the middle reaches of the Heihe River Basin.
基金sponsored by the National Natural Science Foundation of China (91025015)
文摘The runoff generated from mountainous regions is recognized as the main water source for inland river basins in arid environments. Thus, the mechanisms by which catchments retain water in soils are to be understood. The water storage capacity of soil depends on its depth and capacity to retain water under gravita- tional drainage and evapotranspiration. The latter can be studied through soil water retention curve （SWRC）, which is closely related to soil properties such as texture, bulk density, porosity, soil organic carbon conteMt, and so on. The present study represented SWRCs using HYDRUS-1D. In the present study, we measured pl^ysical and hydraulic properties of soil samples collected from Sabina przewalskii forest （south-facing slope with highest solar radiation）, shrubs （west-facing slope with medium radiation）, and Picea crassifolia forest （north-facing slope with lowest radiation）, and analyzed the differences in soil water storage capacity of these soil samples. Soil water content of those three vegetation covers were also measured to validate the soil water storage capacity and to analyze the relationship between soil organic matter content and soil water content. Statistical analysis showed that different vegetation covers could lead to different soil bulk densities and differences in soil water retention on the three slope aspects. Sand content, porosity, and organic carbon content of the P. crassifolia forest were rela- tively greater compared with those of the S. przewalskii forest and shrubs. However, silt content and soil bulk density were relatively smaller than those in the S. przewalskii forest and shrubs. In addition, there was a sig- nificant linear positive relationship between averaged soil water content and soil organic matter content （P〈0.0001）. However, this relationship is not significant in the P. crassifolia forest. As depicted in the SWRCs, the water storage capacity of the soil was 39.14% and 37.38% higher in the P. crassifolia forest than in the S. przewalskii
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant Nos. 40901202, 40925004）, and the National High Technology Research and Development Program of China （Grant No. 2009AA122104）. The input data for WRF model are from the Research Data Archive （RDA） which is maintained by the Computational and Information Systems Laboratory （CISL） at the National Center for Atmo- spheric Research （NCAR）. The original data are available from the RDA （http：//dss.ucar.edu） in Dataset No. ds083.2.
文摘The spatial resolution of general circulation models （GCMs） is too coarse to represent regional climate variations at the regional, basin, and local scales required for many environmental modeling and impact assessments. Weather research and forecasting model （WRF） is a nextgeneration, fully compressible, Euler non-hydrostatic mesoscale forecast model with a runtime hydrostatic option. This model is useful for downscaling weather and climate at the scales from one kilometer to thousands of kilometers, and is useful for deriving meteorological parameters required for hydrological simulation too. The objective of this paper is to validate WRF simulating 5 km/ 1 h air temperatures by daily observed data of China Meteorological Administration （CMA） stations, and by hourly in-situ data of the Watershed Allied Telemetry Experimental Research Project. The daily validation shows that the WRF simulation has good agreement with the observed data; the R2 between the WRF simulation and each station is more than 0.93; the absolute of meanbias error （MBE） for each station is less than 2℃; and the MBEs of Ejina, Mazongshan and Alxa stations are near zero, with R2 is more than 0.98, which can be taken as an unbiased estimation. The hourly validation shows that the WRF simulation can capture the basic trend of observed data, the MBE of each site is approximately 2℃, the R2 of each site is more than 0.80, with the highest at 0.95, and the computed and observed surface air temperature series show a significantly similar trend.
基金supported by the National Natural Science Foundation of China(Grant No.91225302)
文摘Modeling the hydrological processes at catchment scale requires a flexible distributed scheme to represent the catchment to- pography, river network and vegetation pattern. This study has developed a distributed scheme for eco-hydrological simulation in the upper Heihe River. Based on a 1 km x 1 km grid system, the study catchment is divided into 461 sub-catchments, whose main streams form the streamflow pathway. Furthermore, a 1 km grid is represented by a number of topographically similar ＂hillslope-valley＂ systems, and the hillslope is the basic unit of the eco-hydrological simulation. This model is tested with a simplified hydrological simulation focusing on soil-water dynamics and streamflow routing. Based on a 12-year simulation from 2001 to 2012, it is found that variability in hydrological behavior is closely associated with climatic and landscape condi- tions especially vegetation types. The subsurface and groundwater flows dominate the total river runoff. This implies that the soil freezing and thawing process would significantly influence the runoff generation in the upper Heihe basin. Furthermore, the runoff components and water balance characteristics vary among different vegetation types, showing the importance of coupling the vegetation pattern into catchment hydrological simulation. This paper also discusses the model improvement to be done in future study.
基金supported by the National Basic Research Program of China(2010CB950702)the National High Technology Research and Development Program of China(2007AA10Z231)+2 种基金the National Natural Science Foundation of China(40871012,J1103512,J1210026)the Asia-Pacific Network(ARCP-2012-SP25-Li)the Australian Agency for International Development(64828)
文摘Relative roles of climate change and human activities in desertification are the hotspot of research on desertification dynamic and its driving mechanism.To overcome the shortcomings of existing studies,this paper selected net primary productivity （NPP） as an indicator to analyze desertification dynamic and its impact factors.In addition,the change trends of actual NPP,potential NPP and HNPP （human appropriation of NPP,the difference between potential NPP and actual NPP） were used to analyze the desertification dynamic and calculate the relative roles of climate change,human activities and a combination of the two factors in desertification.In this study,the Moderate Resolution Imaging Spectroradiometer （MODIS）-Normalised Difference Vegetation Index （NDVI） and meteorological data were utilized to drive the Carnegie-Ames-Stanford Approach （CASA） model to calculate the actual NPP from 2001 to 2010 in the Heihe River Basin.Potential NPP was estimated using the Thornthwaite Memorial model.Results showed that 61％ of the whole basin area underwent land degradation,of which 90.5％ was caused by human activities,8.6％ by climate change,and 0.9％ by a combination of the two factors.On the contrary,1.5％ of desertification reversion area was caused by human activities and 90.7％ by climate change,the rest 7.8％ by a combination of the two factors.Moreover,it was demonstrated that 95.9％ of the total actual NPP decrease was induced by human activities,while 69.3％ of the total actual NPP increase was caused by climate change.The results revealed that climate change dominated desertification reversion,while human activities dominated desertification expansion.Moreover,the relative roles of both climate change and human activities in desertification possessed great spatial heterogeneity.Additionally,ecological protection policies should be enhanced in the Heihe River Basin to prevent desertification expansion under the condition of climate change.
文摘Climatic change has significant impacts on snow cover in mid-latitude mountainous re- gions, in the meantime, spatial and temporal changes of snow cover and snowmelt runoffs are con- sidered as sensitive indicators for climatic change. In this study, the upper Heihe Watershed in the Qilian Mountains was selected as a typical area affected by snow cover and snowmelt runoffs in northwestern China. The changes in air temperatures, precipitation, snowfall and spring snowmelt runoffs were analyzed for the period from 1956 to 2001. The results indicate that climatic warming was apparent, particularly in January and February, but precipitation just fluctuated without a clear trend. The possible changes of snowmelt runoffs in the upper Heihe watershed in response to a warming of 4℃ were simulated using Snowmelt Runoff Model (SRM) based on the degree-day factor algorithm. The results of the simulation indicate that a forward shifting of snow melting season, an increase in water flows in earlier melting season, and a decline in flows in later melting season would occur under a 4℃ warming scenario.
基金National Key R&D Program of China,No.2017YFA0604704
文摘The Heihe River Basin is located in the arid and semi-arid regions of Northwest China.Here,the terrestrial ecosystem is vulnerable,making it necessary to identify the factors that could affect the ecosystem.In this study,MODIS-NDVI data with a 250-m resolution were used as a proxy for the terrestrial ecosystem.By combining these with environmental factors,we were able to explore the spatial features of NDVI and identify the factors influencing the NDVI distribution in the Heihe River Basin during the period of 2000–2016.A geographical detector(Geodetector) was employed to examine the spatial heterogeneity of the NDVI and to explore the factors that could potentially influence the NDVI distribution.The results indicate that:(1) the NDVI in the Heihe River Basin appeared high in the southeast while being low in the north,showing spatial heterogeneity with a q-statistic of 0.38.The spatial trend of the vegetation in the three sub-basins generally increased in the growing seasons from 2000 to 2016;(2) The results obtained by the Geodetector(as denoted by the q-statistic as well as the degree of spatial association between the NDVI and environmental factors) showed spatial heterogeneity in the associations between the NDVI and the environmental factors for the overall basin as well as the sub-basins.Precipitation was the dominant factor for the overall basin.In the upper basin,elevation was found to be the dominant factor.The dominant factor in the middle basin was precipitation,closely followed by the soil type.In the lower basin,the dominant factor was soil type with a lower q-statistic of 0.13,and the dominant interaction between the elevation and soil type was nonlinearly enhanced(q-statistic = 0.22).
基金funded by the National Natural Science Foundation of China (40971032, 91125026)
文摘High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk（Tamarix ramosissima） is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian for
基金This work was supported by the Knowledge Innovation Program from the Cold and Add Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences （CACX2003102）the Chinese Academy of Sciences （KZCX 1 - 10-03-01）the National Natural Science Foundation of China （40401012）.
文摘Based on the data for meteorology, hydrology, soil, planting, vegetation, and socio-economic development of the irrigation region in the middle reaches of the Heihe River basin, Northwest China, the model of balance of water supply and demand in the region was established, and the security of water resource was assessed, from which the results that the effects of unified management of water resources in the Heihe River basin between Gansu Province and Inner Mongolia on regional hydrology are significant with a decrease in water supply diverted from Heihe River and an increase in groundwater extracted. In addition, it was found that the groundwater level has been steadily decreasing due to over pumping and decrease in recharges. In present year （2003）, the volume of potential groundwater in the irrigation districts is far small because of the groundwater overdraft; even in the particular regions, there is no availability of groundwater resources for use. By 2003, water supply is not sufficient to meet the water demand in the different irrigation districts, the sustainable development and utilization of water resources are not secured, and the water supply crisis occurs in Pingchuan irrigation district. Achieving water security for the sustainable development of society, agriculture, economy, industry, and livelihoods while maintaining or improving the abilities of the management and planning of water resources, determining of the reasonable percentage between water supply and groundwater utilization and water saving in agricultural irrigation are taken into account. If this does not occur, it is feared that the present performance of water development and planning may further aggravate the problem of scarcities of water resources and further damage the fragile ecological system.
基金The Strategic Priority Research Program of Chinese Academy of Sciences,No.XDA20100104
文摘Land use and cover change(LUCC) is an important indicator of the human-earth system under climate/environmental change,which also serves as a key impact factor of carbon balance,and a major source/sink of soil carbon cycles.The Heihe River Basin(HRB) is known as a typical ecologically fragile area in the arid/semi-arid regions of northwestern China,which makes it more sensitive to the LUCC.However,its sensitivity varies in a broad range of controlling factors,such as soil layers,LUCCs and calculation methods(e.g.the fixed depth method,FD,and the equivalent mass method,ESM).In this study,we performed a meta-analysis to assess the response of soil organic carbon(SOC) and total nitrogen(TN) storage to the LUCC as well as method bias based on 383 sets of SOC data and 148 sets of TN data from the HRB.We first evaluated the calculation methods and found that based on the FD method,the LUCC caused SOC and TN storage to decrease by 17.39% and 14.27%,respectively;while the losses estimated using the ESM method were 19.31% and 18.52%,respectively.The deviations between two methods were mainly due to the fact that the FD method ignores the heterogeneity of soil bulk density(BD),which may underestimate the results subsequently.We then analyzed the response of SOC and TN storage to various types of the LUCC.In particular,when woodland and grassland were converted into cultivated land or other land types,SOC and TN suffered from heavy losses,while other LUCCs had minor influences.Finally,we showed that increasing the depth of the soil layers would reduce the losses of SOC and TN storage.In summary,we identified a series of controlling factors(e.g.soil layer,the LUCC and calculation method) to evaluate the impact of the LUCC on SOC and TN storage in the HRB,which should be considered in future research.
基金Funds for Creative Research Groups of China,No.41121001 Project for Incubation of Specialists in Glaciology and Geocryology of National Natural Science Foundation of China,No.J1210003/J0109+1 种基金 National Natural Science Foundation of China,No.41340014 National Basic Research Program of China,No.2013CBA01801
文摘The Heihe River Basin is the second largest inland river basin in Northwest China and it is also a hotspot in arid hydrology, water resources and other aspects of researches in cold regions. In addition, the Heihe River Basin has complete landscape, moderate watershed size, and typical social ecological environmental problems. So far, there has been no detailed assessment of glaciers change information of the whole river basin. 1：50,000 topographic map data, Landsat TM/ETM＋ remote sensing images and digital elevation model data were used in this research. Through integrated computer automatic interpretation and visual interpretation methods, the object-oriented image feature extraction method was applied to extract glacier outline information. Glaciers change data were derived from analysis, and the glacier variation and its response to climate change in the period 1956/1963–2007/ 2011 were also analyzed. The results show that：（1） In the period 1956/1963–2007/2011, the Heihe River Basin＇s glaciers had an evident retreat trend, the total area of glaciers decreased from 361.69 km2 to 231.17 km^2; shrinking at a rate of 36.08%, with average single glacier area decrease 0.14 km^2; the total number of the glaciers decreased from 967 to 800.（2） Glaciers in this basin are mainly distributed at elevations of 4300–4400 m, 4400–4500 m and 4500–4600 m; and there are significant regional differences in glaciers distribution and glaciers change.（3） Compared with other western mountain glaciers, glaciers retreat in the Heihe River Basin has a higher rate.（4） Analysis of the six meteorological stations＇ annual average temperature and precipitation data from 1960 to 2010 suggests that the mean annual temperature increased significantly and the annual precipitation also showed an increasing trend. It is concluded that glacier shrinkage is closely related with temperature rising, besides, glacier melting caused by rising temperatures greater than glacier mass supply by increased precipitation to
基金supported by grant from the National High Technology Research and Development Program (863) of China (Grant No.2009AA122104)grants from the National Natural Science Foundation of China (No.40901202, No.40925004)+1 种基金supported by the CAS Action Plan for West Development Program (Grant No.KZCX2-XB2-09)Chinese State Key Basic Research Project (Grant No.2007CB714400)
文摘The research of coupling WRF （Weather Research and Forecasting Model） with a land surface model is enhanced to explore the interaction of the atmosphere and land surface; however, regional applicability of WRF model is questioned. In order to do the validation of WRF model on simulating forcing data for the Heihe River Basin, daily meteorological observation data from 15 stations of CMA （China Meteorological Administration） and hourly meteorological observation data from seven sites of WATER （Watershed Airborne Telemetry Experimental Research） are used to compare with WRF simulations, with a time range of a whole year for 2008. Results show that the average MBE （Mean Bias Error） of daily 2-m surface temperature, surface pressure, 2-m relative humidity and 10-m wind speed were -0.19 ℃, -4.49 hPa, 4.08% and 0.92 m/s, the average RMSE （Root Mean Square Error） of them were 2.11 ℃, 5.37 hPa, 9.55% and 1.73 m/s, and the average R （correlation coefficient） of them were 0.99, 0.98, 0.80 and 0.55, respectively. The average MBE of hourly 2-m surface temperature, surface pressure, 2-m relative humidity, 10-m wind speed, downward shortwave radiation and downward longwave were-0.16 ℃,-6.62 hPa,-5.14%, 0.26 m/s, 33.0 W/m^2 and-6.44 W/m^2, the average RMSE of them were 2.62 ℃, 17.10 hPa, 20.71%, 2.46 m/s, 152.9 W/m^2 and 53.5 W/m^2, and the average R of them were 0.96, 0.97, 0.70, 0.26, 0.91 and 0.60, respectively. Thus, the following conclusions were obtained： （1） regardless of daily or hourly validation, WRF model simulations of 2-m surface temperature, surface pressure and relative humidity are more reliable, especially for 2-m surface air temperature and surface pressure, the values of MBE were small and R were more than 0.96; （2） the WRF simulating downward shortwave radiation was relatively good, the average R between WRF simulation and hourly observation data was above 0.9, and the average R of downward longwave radiation was 0.6; （3） both wind speed and rainfall simulated fr
基金supported financially by the National Natural Science Foundation of China(Grant No.91025025)National Basic Research Program of China(Grant.No.2010CB951003)
文摘The object of this paper is the different plant communities in the Ejina desert riparian forest. Groundwater depth, soil moisture, plant water potential, relative leaf moisture content and water use efficiency was monitored, and the response of soil moisture and plant ecology to the groundwater depth and the water use efficiency of the different plant communities was analyzed. The results showed that：（1） Along with the groundwater depth increasing, predawn and midday water potential of the plants, with the exception of Reaumuria soongorica, did not decrease significantly, indicating that when the groundwater depth is less than 3 m, the plant communities in the range of 4 km from the river way did not suffer or slightly suffer from water stress;（2） The distribution of higher soil moisture content within 0–3 m soil layer is suitable with the plants’ root system, as indicated in the communities of coexisting overripe Populus euphratica or Taramrix chinensis, both of which can release excessive water into soil for shallow rooted shrubs or herbaceous plants when there is water shortage;（3） R. soongorica can absorb deep soil moisture through deep roots for their own survival;（4） The community consisting of Sophora alopecuroides, Karelinia caspica, T. chinensis, and overripe P. euphratica has the best species combination for restoring the damaged eco-environment in the lower reaches of Heihe River;（5） The order of plants’ relative leaf water contents is K. caspica ＆gt; S. alopecuroides ＆gt; young P. euphratica ＆gt; overripe P. euphratica ＆gt; mature P. euphratica = T. chinensis coexisting with other species ＆gt; single R. soongorica ＆gt; single T. chinensis and the order of WUE is single T. chinensis ＆gt; single R. soongorica ＆gt; T. chinensis living in symbiosis with other species ＆gt; S. alopecuroides = young P. euphratica ＆gt; mature P. euphratica ＆gt; overripe P. euphratica ＆gt; K. caspica. Therefore, with ample soil moisture, the plant community helps rapid growth
文摘[Objective] The effect of climate change on wetland ecological environment in Heihe River basin was researched.[Method] Based on meteorological data from six meteorological stations in Heihe River basin from 1959 to 2009,the effect of climate change on wetland ecological environment in Heihe River basin in recent 51 years was studied by means of statistical method.[Result] Temperature and precipitation in Heihe River basin showed obvious increasing trend in recent 51 years,especially in recent 20 years;climate change made Heihe River basin more and more dry,specially in mountain area;wetland ecological environment closely related to climate responded to climate change,such as groundwater level rise,wetland area decrease,agriculture planting structure change,meteorological disaster increase,destroyed biodiversity and so on.[Conclusion] Our study had important significance for the protection and development of wetland resources.
