The hydrological processes of mountainous watersheds in inland river basins are complicated.It is absolutely significant to quantify mountainous runoff for social,economic and ecological purposes.This paper takes the ...The hydrological processes of mountainous watersheds in inland river basins are complicated.It is absolutely significant to quantify mountainous runoff for social,economic and ecological purposes.This paper takes the mountainous watershed of the Heihe Mainstream River as a study area to simulate the hydrological processes of mountainous watersheds in inland river basins by using the soil and water assessment tool(SWAT)model.SWAT simulation results show that both the Nash–Sutcliffe efficiency and the determination coefficient values of the calibration period(January 1995 to December 2002)and validation period(January 2002 to December 2009)are higher than 0.90,and the percent bias is controlled within±5%,indicating that the simulation results are satisfactory.According to the SWAT performance,we discussed the yearly and monthly variation trends of the mountainous runoff and the runoff components.The results show that from 1996 to 2009,an indistinctive rising trend was observed for the yearly mountainous runoff,which is mainly recharged by lateral flow,and followed by shallow groundwater runoff and surface runoff.The monthly variation demonstrates that the mountainous runoff decreases slightly from May to July,contrary to other months.The mountainous runoff is mainly recharged by shallow groundwater runoff in January,February,and from October to December,by surface runoff in March and April,and by lateral flow from May to September.展开更多
The regional climate model RegCM3 incorporating the crop model CERES,called the RegCM3CERES model,was used to study the efects of crop growth and development on regional climate and hydrological processes over seven r...The regional climate model RegCM3 incorporating the crop model CERES,called the RegCM3CERES model,was used to study the efects of crop growth and development on regional climate and hydrological processes over seven river basins in China.A 20-year numerical simulation showed that incorporating the crop growth and development processes improved the simulation of precipitation over the Haihe River Basin,Songhuajiang River Basin and Pearl River Basin.When compared with the RegCM3 control run,RegCM3CERES reduced the negative biases of monthly mean temperature over most of the seven basins in summer,especially the Haihe River Basin and Huaihe River Basin.The simulated maximum monthly evapotranspiration for summer(JJA)was around 100 mm in the basins of the Yangtze,Haihe,Huaihe and Pearl Rivers.The seasonal and annual variations of water balance components(runof,evapotranspiration and total precipitation)over all seven basins indicate that changes of evapotranspiration agree well with total precipitation.Compared to the RegCM3,RegCM3CERES simulations indicate reduced local water recycling rate over most of the seven basins due to lower evapotranspiration and greater water flux into these basins and an increased precipitation in the Heihe River Basin and Yellow River Basin,but reduced precipitation in the other five basins.Furthermore,a lower summer leaf area index(1.20 m2m 2),greater root soil moisture(0.01 m3m 3),lower latent heat flux(1.34 W m 2),and greater sensible heat flux(2.04 W m 2)are simulated for the Yangtze River Basin.展开更多
In this paper, a novel and efficient study on the hydrological processes of storm runoff from catchments of different land uses is conducted. The motivation is to precisely simulate the hydrological processes of storm...In this paper, a novel and efficient study on the hydrological processes of storm runoff from catchments of different land uses is conducted. The motivation is to precisely simulate the hydrological processes of storm runoff in the agricultural catchments with different patterns of land uses, i.e., forest, paddy, and upland, respectively. As it is discussed in this paper, different land use leads to different characteristics of storm runoff. In order to understand the changes in the hydrological processes of storm runoff from catchments of different land uses, the effects of rainfall intensity, initial soil moisture deficit, evapotranspiration rate, percolation rate, and retention capacity on hydrological processes of the catchments are taken into consideration. According to the principle of water balance, a general model to connect the separate hydrological processes is developed; then, the individual hydrological process is studied in detail: Firstly, the daily evaporation is calculated according to the relation between the actual evapotranspiration and the potential evapotranspiration rate; Secondly, the retention of storm runoff is plotted against the total rainfall, and the maximum storage is calculated; Thirdly, the percolation rate is calculated for each catchment.展开更多
Continental Flood Basalts(CFB)occupy one fourth of the world’s land area.Hence,it is important to discern the hydrological processes in this complex hydrogeological setup for the sustainable water resources developme...Continental Flood Basalts(CFB)occupy one fourth of the world’s land area.Hence,it is important to discern the hydrological processes in this complex hydrogeological setup for the sustainable water resources development.A model assisted isotope,geochemical,geospatial and geophysical study was conducted to understand the monsoonal characteristics,recharge processes,renewability and geochemical evolution in one of the largest continental flood basalt provinces of India.HYSPLIT modelling and stable isotopes were used to assess the monsoonal characteristics.Rayleigh distillation model were used to understand the climatic conditions at the time of groundwater recharge.Lumped parameter models(LPM)were employed to quantify the mean transit time(MTT)of groundwater.Statistical and geochemical models were adopted to understand the geochemical evolution along the groundwater flow path.A geophysical model was used to understand the geometry of the aquifer.The back trajectory analysis confirms the isotopic finding that precipitation in this region is caused by orographic uplifting of air masses originating from the Arabian Sea.Stable isotopic data of groundwater showed its meteoric origin and two recharge processes were discerned;(i)quick and direct recharge by precipitation through fractured and weathered basalt,(ii)low infiltration through the clayey black cotton soil and subjected to evaporation prior to the recharge.Tritium data showed that the groundwater is a renewable source and have shorter transit times(from present day to<30 years).The hydrogeochemical study indicated multiple sources/processes such as:the minerals dissolution,silicate weathering,ion exchange,anthropogenic influences etc.control the chemistry of the groundwater.Based on the geo-electrical resistivity survey,the potential zones(weathered and fractured)were delineated for the groundwater development.Thus,the study highlights the usefulness of model assisted isotopic hydrogeochemical techniques for understanding the recharge and geochemical processes in a basaltic aquifer system.展开更多
Debris flow runoff process is one of key parameters for the design of emergency measures and control engineering. The Shenxi gully in Dujiangyan region,located in the meizoseismal areas of Wenchuan earthquake,was sele...Debris flow runoff process is one of key parameters for the design of emergency measures and control engineering. The Shenxi gully in Dujiangyan region,located in the meizoseismal areas of Wenchuan earthquake,was selected as the study area. Based on the research of hazard inducing environment,a soil conservation service( SCS) hydrological model was used to simulate the process of water flow,and then the debris flow runoff process was calculated using the empirical formula combining the results from the SCS hydrological model. Taking the debris flow event occurred on July 9th,2013 as an example,the peak discharges of water flow and debris flow were calculated as 162. 12 and 689. 22 m3/s,with error of 6. 03% compared to the measured values. The debris flow confluence process lasted 1. 8h, which was similar with the actual result. The proposed methodology can be applied to predict the debris flow runoff process in quake-hit areas of the Wenchuan earthquake and is of great importance for debris flow mitigation.展开更多
Present studies on the coupling relationship and hydrology mechanism between basin ecosystem and hydrological process has become an international research frontier in hydrology. This paper investigates this coupling r...Present studies on the coupling relationship and hydrology mechanism between basin ecosystem and hydrological process has become an international research frontier in hydrology. This paper investigates this coupling relationship, and also summarizes research and presents a method of combining isotopic technology with hydro-chemical methods, for the study of eco-hydrological process and function in different landscape zones. We then examine research trends for future direction and development of this field.展开更多
This paper investigates the hydrological interactions in the atmosphere-evegetation-soil system by using the bucket model and several new simplified intermediately complex models. The results of mathematical analysis ...This paper investigates the hydrological interactions in the atmosphere-evegetation-soil system by using the bucket model and several new simplified intermediately complex models. The results of mathematical analysis and numerical simulations show that these models, despite their simplicity, can very clearly reveal the essential features of the rather complex hydrological system of atmosphere-ecosystem-soil. For given atmospheric variables, these models clearly demonstrate multiple timescales, the "red shift" of response spectra, multi-equilibria and limit cycles, bifurcation, abrupt change, self-organization, recovery, "desertification", and chaos. Most of these agree with observations. Especially, the weakening of "shading effect" of living canopy and the wilted biomass might be a major mechanism leading to the desertification in a relatively short period due to overgrazing, and the desertification in a relatively long period or in climate of change might be due to both Charney's mechanism and the shading effect. These ideas could be validated with further numerical simulations. In the paper, some methods for improving the estimation of timescales in the soil water evolution responding to the forcing are also proposed.展开更多
Englacial and subglacial drainage systems of temperate glaciers have a strong influence on glacier dynamics, glacier-induced floods, glacier-weathering processes, and runoff from glacierized drainage basins. Proglacia...Englacial and subglacial drainage systems of temperate glaciers have a strong influence on glacier dynamics, glacier-induced floods, glacier-weathering processes, and runoff from glacierized drainage basins. Proglacial discharge is partly controlled by the geometry of the glacial drainage network and by the process of producing meltwater. The glacial-drainage system of some alpine glaciers has been characterized using a model based on proglacial discharge analysis. In this paper, we apply cross-correlation analysis to hourly hydro-climatic data collected from China's Hailuogou Glacier, a typical temperate glacier in Mt. Gongga, to study the seasonal status changes of the englacial and subglacial drainage systems by discharge-temperature (Q-T) time lag analy-sis. During early ablation season (April-May) of 2003, 2004 and 2005, the change of englacial and subglacial drainage system usually leads several outburst flood events, which are also substantiated by observing the leakage of supraglacial pond and cre-vasses pond water during field works in April, 2008. At the end of ablation season (October-December), the glacial-drainage net-works become less hydro-efficient. Those events are evidenced by hourly hydro-process near the terminus of Hailuogou Glacier, and the analysis of Q-T time lags also can be a good indicator of those changes. However, more detailed observations or experi-ments, e.g. dye-tracing experiment and recording borehole water level variations, are necessary to describe the evolutionary status and processes of englacial and subglacial drainage systems evolution during ablation season.展开更多
In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ i...In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ in OTC-1 and 3-5℃ in OTC-2 in the alpine meadow ecosystem on the Qinghai- Tibetan Plateau.Results show that the annual air temperatures under OTC-1 and OTC-2 were 1.21℃ and 3.62℃ higher than the Control,respectively.The entirely-frozen period of shallow soil in the active layer was shortened and the fully thawed period was prolonged with temperature increase.The maximum penetration depth and duration of the negative isotherm during the entirely-frozen period decreased, and soil freezing was retarded in the local scope of the soil profile when temperature increased.Meanwhile, the positive isotherm during the fully-thawed period increased,and the soil thawing was accelerated.Soil moisture under different manipulations decreased with the temperature increase at the same depth. During the early freezing period and the early fully- thawed period,the maximum soil moisture under the Control manipulation was at 0.2 m deep,whereas under OTC-1 and OTC-2 manipulations,the maximum soil moisture were at 0.4-0.5 m deep. These results indicate that elevated temperatures led to a decrease of the moisture in the surface soil.The coupled relationship between soil temperature and moisture was significantly affected by the temperature increase.During the freezing and thawing processes, the soil temperature and moisture under different manipulations fit the regression model given by the equationθV=a/{1+exp[b(TS+c)]}+d.展开更多
Based on previous research results on river re-distribution models, a modification on the effects of topographic slopes for a runoff parameterization was proposed and implemented to the NCAR's land sur- face model...Based on previous research results on river re-distribution models, a modification on the effects of topographic slopes for a runoff parameterization was proposed and implemented to the NCAR's land sur- face model (LSM). This modification has two aspects firstly, the topographic slopes cause outflows from higher topography and inflows into the lower topography points; secondly, topographic slopes also cause decrease of infiltration at higher topography and increases of infiltration at lower topography. Then changes in infiltration result in changes in soil molsture, surface fluxes and then in surface temperature, and eventual- ly in the upper atmosphere and the climate. This mechanism is very clearly demonstrated in the point bud- gets analysis at the Andes Mountains vicinities. Analysis from a regional scale perspective in the Mackenzie GEWEX Study (MAGS) area, the focus of the ongoing Canadian GEWEX program, shows that the modi- fied runoff parameterization does bring significant changes in the regional surface climate More important- ly, detailed analysis from a global perspective shows many encouraging improvements introduced by the modified LSM over the original model in simulating basic atmospheric climate properties such as thermodynamic features (temperature and humidity). All of these improvements in the atmospheric climate simulation illustrate that the inclusion of topographic effects in the LSM can force the AGCM to produce a more realistic model climate.展开更多
The hydrological characteristics of the Heihe River Basin in the arid inland area of northwest China were investigated.The spatial distribution of annual precipitation in the basin indicates that it decreases from eas...The hydrological characteristics of the Heihe River Basin in the arid inland area of northwest China were investigated.The spatial distribution of annual precipitation in the basin indicates that it decreases from east to west and from south to north,and increases with elevation by a gradient of 24.4 mm per hundred meters below 2,810 m a.s.l.,but decreases with elevation by that of 37.0 mm per hundred meters above 2,810 m a.s.l.For the last 50 years,the mountain runoff of the ba-sin has a tendency of increase.Except in the mountain area,the aridity is very high in the basin,and the aridity index ranges from 1.6 to 7.0 at the piedmont,to 9.0~20.0 in the midstream area and up to 40.0 in the downstream Ejin region.It is estimated for the last 50 years that a 1oC increment of annual temperature causes a 21.5 mm increase of evaporation in the mountain area,and the equivalent reduction of mountain runoff is 0.215×109 m3/yr at the Yingluoxia Hydrometric Sta-tion.The estimation shows also that a 1oC increment of annual temperature causes 1,842 mm increase of farmland evapotranspiration in the midstream area,an equivalent of 0.298×109 m3/yr more water consumption.The anthropogenic influence on the hydrological processes and water resources is then discussed.展开更多
Hydrological modeling,leveraging mathematical formulations to represent the hydrological cycle,is a pivotal tool in representing the spatiotemporal dynamics and distribution patterns inherent in hydrology.These models...Hydrological modeling,leveraging mathematical formulations to represent the hydrological cycle,is a pivotal tool in representing the spatiotemporal dynamics and distribution patterns inherent in hydrology.These models serve a dual purpose:they validate theoretical robustness and applicability via observational data and project future trends,thereby bridging the understanding and prediction of natural processes.In rapid advancements in computational methodologies and the continuous evolution of observational and experimental techniques,the development of numerical hydrological models based on physicallybased surface-subsurface process coupling have accelerated.Anchored in micro-scale conservation principles and physical equations,these models employ numerical techniques to integrate surface and subsurface hydrodynamics,thus replicating the macro-scale hydrological responses of watersheds.Numerical hydrological models have emerged as a leading and predominant trend in hydrological modeling due to their explicit representation of physical processes,heightened by their spatiotemporal resolution and reliance on interdisciplinary integration.This article focuses on the theoretical foundation of surface-subsurface numerical hydrological models.It includes a comparative and analytical discussion of leading numerical hydrological models,encompassing model architecture,numerical solution strategies,spatial representation,and coupling algorithms.Additionally,this paper contrasts these models with traditional hydrological models,thereby delineating the relative merits,drawbacks,and future directions of numerical hydrological modeling.展开更多
Discharge characteristics are crucial for detecting changes in hydrological processes.Recently,the river hydrology)in the Headwater Area of the Yellow River(HAYR)has exhibited erratic regimes(e.g.,monotonously declini...Discharge characteristics are crucial for detecting changes in hydrological processes.Recently,the river hydrology)in the Headwater Area of the Yellow River(HAYR)has exhibited erratic regimes(e.g.,monotonously declining/low/high hydrograph,even with normal precipitation)under the effects of climate change,permafrost thaw and changes in dam operation.This study integrates hydroclimatic variables(air temperature,precipitation,and potential evapotranspiration)with anthropogenic dam operation and permafrost degradation impact data to systematically examine the mechanisms of these hydrological process changes during 1956–2019.The results show the following:1)compared with the pre-dammed gauged flow,dam construction(January 1998–January 2000)and removal of dam(September 2018–August 2019)induced monotonously low(−17.2 m^(3) s^(−1);−61%)and high(+54.6 m^(3) s^(−1);+138%)hydrographs,respectively;2)hydroclimatic variables mainly controlled the summer–autumn hydrological processes in the HAYR;3)the monotonous decline of the hydrograph of Yellow River in the HAYR in some hydrological years(e.g.,1977,1979,1990 and 1995)was closely related with unusually high atmospheric demands of evaporation and low-intense rainfall during summer–autumn seasons;and 4)the lengthening of subsurface hydrological pathways and residence time,permafrost degradation reduced the recession coefficient(−0.002 per year)of winter flow and altered the hydrological regimes of seasonal rivers,which resulted in flattened hydrographs that reduced and delayed the peak flow(of 0.05 mm per year and 1.65 d per year,respectively)as well as boosted the winter baseflow(0.01 mm per year).This study can provide updated and systematic understanding of changing hydrological processes in typical alpine catchments on northeastern Qinghai–Tibet Plateau,China under a warming climate.展开更多
基金supported by the National Natural Science Foundation of China(41240002,91125025,91225302,Y211121001)the National Science and Technology Support Projects(2011BAC07B05)
文摘The hydrological processes of mountainous watersheds in inland river basins are complicated.It is absolutely significant to quantify mountainous runoff for social,economic and ecological purposes.This paper takes the mountainous watershed of the Heihe Mainstream River as a study area to simulate the hydrological processes of mountainous watersheds in inland river basins by using the soil and water assessment tool(SWAT)model.SWAT simulation results show that both the Nash–Sutcliffe efficiency and the determination coefficient values of the calibration period(January 1995 to December 2002)and validation period(January 2002 to December 2009)are higher than 0.90,and the percent bias is controlled within±5%,indicating that the simulation results are satisfactory.According to the SWAT performance,we discussed the yearly and monthly variation trends of the mountainous runoff and the runoff components.The results show that from 1996 to 2009,an indistinctive rising trend was observed for the yearly mountainous runoff,which is mainly recharged by lateral flow,and followed by shallow groundwater runoff and surface runoff.The monthly variation demonstrates that the mountainous runoff decreases slightly from May to July,contrary to other months.The mountainous runoff is mainly recharged by shallow groundwater runoff in January,February,and from October to December,by surface runoff in March and April,and by lateral flow from May to September.
基金supported by the National Basic Research Program of China(Nos.2010CB428403 and 2010CB951001)the National Natural Science Foundation of China(No.91125016)
文摘The regional climate model RegCM3 incorporating the crop model CERES,called the RegCM3CERES model,was used to study the efects of crop growth and development on regional climate and hydrological processes over seven river basins in China.A 20-year numerical simulation showed that incorporating the crop growth and development processes improved the simulation of precipitation over the Haihe River Basin,Songhuajiang River Basin and Pearl River Basin.When compared with the RegCM3 control run,RegCM3CERES reduced the negative biases of monthly mean temperature over most of the seven basins in summer,especially the Haihe River Basin and Huaihe River Basin.The simulated maximum monthly evapotranspiration for summer(JJA)was around 100 mm in the basins of the Yangtze,Haihe,Huaihe and Pearl Rivers.The seasonal and annual variations of water balance components(runof,evapotranspiration and total precipitation)over all seven basins indicate that changes of evapotranspiration agree well with total precipitation.Compared to the RegCM3,RegCM3CERES simulations indicate reduced local water recycling rate over most of the seven basins due to lower evapotranspiration and greater water flux into these basins and an increased precipitation in the Heihe River Basin and Yellow River Basin,but reduced precipitation in the other five basins.Furthermore,a lower summer leaf area index(1.20 m2m 2),greater root soil moisture(0.01 m3m 3),lower latent heat flux(1.34 W m 2),and greater sensible heat flux(2.04 W m 2)are simulated for the Yangtze River Basin.
基金Supported by the Natural Science Foundation of Hubei Province (2005ABA290)
文摘In this paper, a novel and efficient study on the hydrological processes of storm runoff from catchments of different land uses is conducted. The motivation is to precisely simulate the hydrological processes of storm runoff in the agricultural catchments with different patterns of land uses, i.e., forest, paddy, and upland, respectively. As it is discussed in this paper, different land use leads to different characteristics of storm runoff. In order to understand the changes in the hydrological processes of storm runoff from catchments of different land uses, the effects of rainfall intensity, initial soil moisture deficit, evapotranspiration rate, percolation rate, and retention capacity on hydrological processes of the catchments are taken into consideration. According to the principle of water balance, a general model to connect the separate hydrological processes is developed; then, the individual hydrological process is studied in detail: Firstly, the daily evaporation is calculated according to the relation between the actual evapotranspiration and the potential evapotranspiration rate; Secondly, the retention of storm runoff is plotted against the total rainfall, and the maximum storage is calculated; Thirdly, the percolation rate is calculated for each catchment.
文摘Continental Flood Basalts(CFB)occupy one fourth of the world’s land area.Hence,it is important to discern the hydrological processes in this complex hydrogeological setup for the sustainable water resources development.A model assisted isotope,geochemical,geospatial and geophysical study was conducted to understand the monsoonal characteristics,recharge processes,renewability and geochemical evolution in one of the largest continental flood basalt provinces of India.HYSPLIT modelling and stable isotopes were used to assess the monsoonal characteristics.Rayleigh distillation model were used to understand the climatic conditions at the time of groundwater recharge.Lumped parameter models(LPM)were employed to quantify the mean transit time(MTT)of groundwater.Statistical and geochemical models were adopted to understand the geochemical evolution along the groundwater flow path.A geophysical model was used to understand the geometry of the aquifer.The back trajectory analysis confirms the isotopic finding that precipitation in this region is caused by orographic uplifting of air masses originating from the Arabian Sea.Stable isotopic data of groundwater showed its meteoric origin and two recharge processes were discerned;(i)quick and direct recharge by precipitation through fractured and weathered basalt,(ii)low infiltration through the clayey black cotton soil and subjected to evaporation prior to the recharge.Tritium data showed that the groundwater is a renewable source and have shorter transit times(from present day to<30 years).The hydrogeochemical study indicated multiple sources/processes such as:the minerals dissolution,silicate weathering,ion exchange,anthropogenic influences etc.control the chemistry of the groundwater.Based on the geo-electrical resistivity survey,the potential zones(weathered and fractured)were delineated for the groundwater development.Thus,the study highlights the usefulness of model assisted isotopic hydrogeochemical techniques for understanding the recharge and geochemical processes in a basaltic aquifer system.
基金Water Resources Science and Technology Innovation Project of Guangdong Province,China(No.2016-15)National Natural Science Foundation of China(No.41372331)Science and Technology Planning Projects of Guangdong Province,China(Nos.2014A020219006,2014A020219006)
文摘Debris flow runoff process is one of key parameters for the design of emergency measures and control engineering. The Shenxi gully in Dujiangyan region,located in the meizoseismal areas of Wenchuan earthquake,was selected as the study area. Based on the research of hazard inducing environment,a soil conservation service( SCS) hydrological model was used to simulate the process of water flow,and then the debris flow runoff process was calculated using the empirical formula combining the results from the SCS hydrological model. Taking the debris flow event occurred on July 9th,2013 as an example,the peak discharges of water flow and debris flow were calculated as 162. 12 and 689. 22 m3/s,with error of 6. 03% compared to the measured values. The debris flow confluence process lasted 1. 8h, which was similar with the actual result. The proposed methodology can be applied to predict the debris flow runoff process in quake-hit areas of the Wenchuan earthquake and is of great importance for debris flow mitigation.
基金supported by the Projects Internation-al Science&Technology Cooperation Program of China(2012DFA20770)National Natural Science Foundation of China(41201043)+1 种基金Natural Science Foundation of Shanxi Province(2012021026-3)Science and Technology Major Projects of Shanxi Province(20121101011)
文摘Present studies on the coupling relationship and hydrology mechanism between basin ecosystem and hydrological process has become an international research frontier in hydrology. This paper investigates this coupling relationship, and also summarizes research and presents a method of combining isotopic technology with hydro-chemical methods, for the study of eco-hydrological process and function in different landscape zones. We then examine research trends for future direction and development of this field.
基金This work was supported by the China National Science foundation (Grant No, 40233027) N0AA 0ffice of Global Programs, NASA (NAGA-13322)+1 种基金the U. S. National Science foundation (ATM 0301188) the Chinese Academy of Sciences' 0verseas Assessor's Grant and Well-Known 0verseas Chinese Scholar Grant.
文摘This paper investigates the hydrological interactions in the atmosphere-evegetation-soil system by using the bucket model and several new simplified intermediately complex models. The results of mathematical analysis and numerical simulations show that these models, despite their simplicity, can very clearly reveal the essential features of the rather complex hydrological system of atmosphere-ecosystem-soil. For given atmospheric variables, these models clearly demonstrate multiple timescales, the "red shift" of response spectra, multi-equilibria and limit cycles, bifurcation, abrupt change, self-organization, recovery, "desertification", and chaos. Most of these agree with observations. Especially, the weakening of "shading effect" of living canopy and the wilted biomass might be a major mechanism leading to the desertification in a relatively short period due to overgrazing, and the desertification in a relatively long period or in climate of change might be due to both Charney's mechanism and the shading effect. These ideas could be validated with further numerical simulations. In the paper, some methods for improving the estimation of timescales in the soil water evolution responding to the forcing are also proposed.
基金supported by the National Natural Science Foundation of China (Grant No. 40801030 and 40801025)the Major State Basic Research Development Program of China (973 Program) (2007CB411506)+1 种基金the Innovation Project of Chinese Academy Sciences (Kzcx2-yw-301)the National Basic Work Program of Chinese MST (Glacier Inventory of China Ⅱ, Grant No. 2006FY110200)
文摘Englacial and subglacial drainage systems of temperate glaciers have a strong influence on glacier dynamics, glacier-induced floods, glacier-weathering processes, and runoff from glacierized drainage basins. Proglacial discharge is partly controlled by the geometry of the glacial drainage network and by the process of producing meltwater. The glacial-drainage system of some alpine glaciers has been characterized using a model based on proglacial discharge analysis. In this paper, we apply cross-correlation analysis to hourly hydro-climatic data collected from China's Hailuogou Glacier, a typical temperate glacier in Mt. Gongga, to study the seasonal status changes of the englacial and subglacial drainage systems by discharge-temperature (Q-T) time lag analy-sis. During early ablation season (April-May) of 2003, 2004 and 2005, the change of englacial and subglacial drainage system usually leads several outburst flood events, which are also substantiated by observing the leakage of supraglacial pond and cre-vasses pond water during field works in April, 2008. At the end of ablation season (October-December), the glacial-drainage net-works become less hydro-efficient. Those events are evidenced by hourly hydro-process near the terminus of Hailuogou Glacier, and the analysis of Q-T time lags also can be a good indicator of those changes. However, more detailed observations or experi-ments, e.g. dye-tracing experiment and recording borehole water level variations, are necessary to describe the evolutionary status and processes of englacial and subglacial drainage systems evolution during ablation season.
基金founded by The National Science Foundation of China(No.40730634 andNo.40925002)
文摘In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ in OTC-1 and 3-5℃ in OTC-2 in the alpine meadow ecosystem on the Qinghai- Tibetan Plateau.Results show that the annual air temperatures under OTC-1 and OTC-2 were 1.21℃ and 3.62℃ higher than the Control,respectively.The entirely-frozen period of shallow soil in the active layer was shortened and the fully thawed period was prolonged with temperature increase.The maximum penetration depth and duration of the negative isotherm during the entirely-frozen period decreased, and soil freezing was retarded in the local scope of the soil profile when temperature increased.Meanwhile, the positive isotherm during the fully-thawed period increased,and the soil thawing was accelerated.Soil moisture under different manipulations decreased with the temperature increase at the same depth. During the early freezing period and the early fully- thawed period,the maximum soil moisture under the Control manipulation was at 0.2 m deep,whereas under OTC-1 and OTC-2 manipulations,the maximum soil moisture were at 0.4-0.5 m deep. These results indicate that elevated temperatures led to a decrease of the moisture in the surface soil.The coupled relationship between soil temperature and moisture was significantly affected by the temperature increase.During the freezing and thawing processes, the soil temperature and moisture under different manipulations fit the regression model given by the equationθV=a/{1+exp[b(TS+c)]}+d.
文摘Based on previous research results on river re-distribution models, a modification on the effects of topographic slopes for a runoff parameterization was proposed and implemented to the NCAR's land sur- face model (LSM). This modification has two aspects firstly, the topographic slopes cause outflows from higher topography and inflows into the lower topography points; secondly, topographic slopes also cause decrease of infiltration at higher topography and increases of infiltration at lower topography. Then changes in infiltration result in changes in soil molsture, surface fluxes and then in surface temperature, and eventual- ly in the upper atmosphere and the climate. This mechanism is very clearly demonstrated in the point bud- gets analysis at the Andes Mountains vicinities. Analysis from a regional scale perspective in the Mackenzie GEWEX Study (MAGS) area, the focus of the ongoing Canadian GEWEX program, shows that the modi- fied runoff parameterization does bring significant changes in the regional surface climate More important- ly, detailed analysis from a global perspective shows many encouraging improvements introduced by the modified LSM over the original model in simulating basic atmospheric climate properties such as thermodynamic features (temperature and humidity). All of these improvements in the atmospheric climate simulation illustrate that the inclusion of topographic effects in the LSM can force the AGCM to produce a more realistic model climate.
基金supported by the West Action Program of Chinese Academy of Sciences (KZCX2-XB2-04-03)the Chinese National Natural Science Fund (40801021)+1 种基金the West Light Foundation of West Doctor of CASthe China Postdoctoral Science Foundation (200801244, 20070420135)
基金supported by a grant from National Natural Sciences Foundation of China (No.40725001 No.40671010)+1 种基金the Key Project (KZCX2-XB2-04-02) of the Chinese Academy of Sciences,the National Key Technology R & D Program (No. 2007BAD46B01)
文摘The hydrological characteristics of the Heihe River Basin in the arid inland area of northwest China were investigated.The spatial distribution of annual precipitation in the basin indicates that it decreases from east to west and from south to north,and increases with elevation by a gradient of 24.4 mm per hundred meters below 2,810 m a.s.l.,but decreases with elevation by that of 37.0 mm per hundred meters above 2,810 m a.s.l.For the last 50 years,the mountain runoff of the ba-sin has a tendency of increase.Except in the mountain area,the aridity is very high in the basin,and the aridity index ranges from 1.6 to 7.0 at the piedmont,to 9.0~20.0 in the midstream area and up to 40.0 in the downstream Ejin region.It is estimated for the last 50 years that a 1oC increment of annual temperature causes a 21.5 mm increase of evaporation in the mountain area,and the equivalent reduction of mountain runoff is 0.215×109 m3/yr at the Yingluoxia Hydrometric Sta-tion.The estimation shows also that a 1oC increment of annual temperature causes 1,842 mm increase of farmland evapotranspiration in the midstream area,an equivalent of 0.298×109 m3/yr more water consumption.The anthropogenic influence on the hydrological processes and water resources is then discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.41930759,42325502)the West Light Foundation of the Chinese Academy of Sciences(Grant No.xbzg-zdsys-202215)+2 种基金the Chinese Academy Sciences Talents Program,National Cryosphere Desert Data Centerthe Qinghai Key Laboratory of Disaster Prevention(Grant No.QFZ-2021-Z02)2023 First Batch of Science and Technology Plan Projects of Lanzhou City(Grant No.2023-1-49)。
文摘Hydrological modeling,leveraging mathematical formulations to represent the hydrological cycle,is a pivotal tool in representing the spatiotemporal dynamics and distribution patterns inherent in hydrology.These models serve a dual purpose:they validate theoretical robustness and applicability via observational data and project future trends,thereby bridging the understanding and prediction of natural processes.In rapid advancements in computational methodologies and the continuous evolution of observational and experimental techniques,the development of numerical hydrological models based on physicallybased surface-subsurface process coupling have accelerated.Anchored in micro-scale conservation principles and physical equations,these models employ numerical techniques to integrate surface and subsurface hydrodynamics,thus replicating the macro-scale hydrological responses of watersheds.Numerical hydrological models have emerged as a leading and predominant trend in hydrological modeling due to their explicit representation of physical processes,heightened by their spatiotemporal resolution and reliance on interdisciplinary integration.This article focuses on the theoretical foundation of surface-subsurface numerical hydrological models.It includes a comparative and analytical discussion of leading numerical hydrological models,encompassing model architecture,numerical solution strategies,spatial representation,and coupling algorithms.Additionally,this paper contrasts these models with traditional hydrological models,thereby delineating the relative merits,drawbacks,and future directions of numerical hydrological modeling.
基金the Chinese Academy of Sciences Strategic Priority Research Program(XDA20100103)the Ministry of Science and Technology of China Key R&D Program(2017YFC0405704)the Autonomous Province of Bozen/Bolzano e Department for Innovation,Research and University in the frame of the Seal of Excellence Program(project TEMPLINK,D55F20002520003).
文摘Discharge characteristics are crucial for detecting changes in hydrological processes.Recently,the river hydrology)in the Headwater Area of the Yellow River(HAYR)has exhibited erratic regimes(e.g.,monotonously declining/low/high hydrograph,even with normal precipitation)under the effects of climate change,permafrost thaw and changes in dam operation.This study integrates hydroclimatic variables(air temperature,precipitation,and potential evapotranspiration)with anthropogenic dam operation and permafrost degradation impact data to systematically examine the mechanisms of these hydrological process changes during 1956–2019.The results show the following:1)compared with the pre-dammed gauged flow,dam construction(January 1998–January 2000)and removal of dam(September 2018–August 2019)induced monotonously low(−17.2 m^(3) s^(−1);−61%)and high(+54.6 m^(3) s^(−1);+138%)hydrographs,respectively;2)hydroclimatic variables mainly controlled the summer–autumn hydrological processes in the HAYR;3)the monotonous decline of the hydrograph of Yellow River in the HAYR in some hydrological years(e.g.,1977,1979,1990 and 1995)was closely related with unusually high atmospheric demands of evaporation and low-intense rainfall during summer–autumn seasons;and 4)the lengthening of subsurface hydrological pathways and residence time,permafrost degradation reduced the recession coefficient(−0.002 per year)of winter flow and altered the hydrological regimes of seasonal rivers,which resulted in flattened hydrographs that reduced and delayed the peak flow(of 0.05 mm per year and 1.65 d per year,respectively)as well as boosted the winter baseflow(0.01 mm per year).This study can provide updated and systematic understanding of changing hydrological processes in typical alpine catchments on northeastern Qinghai–Tibet Plateau,China under a warming climate.