Due to the great influences of both climate warming and human activities,permafrost on the Qinghai-Xizang Plateau(QXP) has been undergoing considerable degradation.Continuous degradation of plateau permafrost dramatic...Due to the great influences of both climate warming and human activities,permafrost on the Qinghai-Xizang Plateau(QXP) has been undergoing considerable degradation.Continuous degradation of plateau permafrost dramatically modifies the regional water cycle and hydrological processes,affecting the hydrogeological conditions,and ground hydrothermal status in cold regions.Permafrost thawing impacts the ecological environment,engineering facilities,and carbon storage functions,releasing some major greenhouse gases and exacerbating climate change.Despite the utilization of advanced research methodologies to investigate the changing hydrological processes and the corresponding influencing factors in permafrost regions,there still exist knowledge gaps in multivariate data,quantitative analysis of permafrost degradation's impact on various water bodies,and systematic hydrological modeling on the QXP.This review summarizes the main research methods in permafrost hydrology and elaborates on the impacts of permafrost degradation on regional precipitation distribution patterns,changes in surface runoff,expansion of thermokarst lakes/ponds,and groundwater dynamics on the QXP.Then,we discuss the current inadequacies and future research priorities,including multiple methods,observation data,and spatial and temporal scales,to provide a reference for a comprehensive analysis of the hydrological and environmental effects of permafrost degradation on the QXP under a warming climate.展开更多
The conceptions of theorems, laws and corollaries of hydrology were put forward. Combining with hydrology practice, several theo- rems, laws as well as corollaries of hydrology were summarized. The study provided some...The conceptions of theorems, laws and corollaries of hydrology were put forward. Combining with hydrology practice, several theo- rems, laws as well as corollaries of hydrology were summarized. The study provided some references for accelerating the development of hydrology theory in these aspects and promoting the improvement of its production technology.展开更多
The complexities of hydrological phenomena, the causes that lead to these complexities, and the essences and defects of reductionism are analyzed. The driving forces for the development of hydrology and the formation ...The complexities of hydrological phenomena, the causes that lead to these complexities, and the essences and defects of reductionism are analyzed. The driving forces for the development of hydrology and the formation of branch subjects of hydrology are discussed. The theoretical basis and limitations of existing hydrology are summarized. Existing misunderstandings in the development of the watershed hydrological model are put forward. Finally, the necessity of the expansion of hydrology from linear to nonlinear is discussed.展开更多
Based on the surface runoff, temperature and precipitation data over the last 50 years from eight representative rivers in Xinjiang, using Mann-Kendall trend and jump detection method, the paper investigated the long-...Based on the surface runoff, temperature and precipitation data over the last 50 years from eight representative rivers in Xinjiang, using Mann-Kendall trend and jump detection method, the paper investigated the long-term trend and jump point of time series, the surface runoff, mean annual temperature and annual precipitation. Meanwhile, the paper analyzed the relationship between runoff and temperature and precipitation, and the flood frequency and peak flow. Results showed that climate of all parts of Xinjiang conformably has experienced an increase in temperature and precipitation since the mid-1980s. Northern Xinjiang was the area that changed most significantly followed by southern and eastern Xinjiang. Affected by temperature and precipitation variation, river runoff had changed both inter-annually and intra-annually. The surface runoff of most rivers has increased significantly since the early 1990s, and some of them have even witnessed the earlier spring floods, later summer floods and increasing flood peaks. The variation characteristics were closely related with the replenishment types of rivers. Flood frequency and peak flow increased all over Xinjiang. Climate warming has had an effect on the regional hydrological cycle.展开更多
Wetlands, one of the most productive systems in the biosphere are a unique ecosystem. They occur in landscapes that favor the ponding or slow runoff of surface water, discharge of ground water, or both. Wetlands are n...Wetlands, one of the most productive systems in the biosphere are a unique ecosystem. They occur in landscapes that favor the ponding or slow runoff of surface water, discharge of ground water, or both. Wetlands are not only important for maintaining plant and animal diversity, but also for balancing global carbon budget via sequestrating or releasing CO2 from/into atmosphere depending on their management. Therefore, it is imperative to understand how wetlands form and function, then we can better manage, utilize, and protect these unique ecosystems. Hydrie soils,hydrophytic vegetation, and wetland hydrology are the three main parameters of wetlands. These parameters are interrelated with each other which jointly influence the development and functions of wetland ecosystems. The objective of this paper was to report the current understanding of wetlands and provide future research directions. The paper will first focus on aspects of hydrology research in wetlands, and then shift to soil hydrosequence and wetland vegetation to better understand processes, structure, and function of wetlands, and conclude with some possible future research directions.展开更多
The use of isotope techniques and methods in catchment hydrology in the last 50 years has generated two major types of progress: (1) Assessment of the temporal variations of the major stocks and flows of water in catc...The use of isotope techniques and methods in catchment hydrology in the last 50 years has generated two major types of progress: (1) Assessment of the temporal variations of the major stocks and flows of water in catchments, from which the estimation of wa-ter residence times is introduced in this paper. (2) Assessment of catchment hydrologic processes, in which the interactions be-tween different waters, hydrographical separation, and bio-geochemical process are described by using isotopes tracers. Future progress on isotope techniques and methods in hydrology is toward the understanding of the hydrological process in large river basins. Much potential also waits realization in terms of how isotope information may be used to calibrate and test distributed rainfall-runoff models and regarding aid in the quantification of sustainable water resources management.展开更多
An analytical expression for subgrid–scale inhomogeneous runoff ratios generated by heterogeneous soil moisture content and climatic precipitation forcing is presented based on physical mechanisms for land surface hy...An analytical expression for subgrid–scale inhomogeneous runoff ratios generated by heterogeneous soil moisture content and climatic precipitation forcing is presented based on physical mechanisms for land surface hydrology and theory of statistical probability distribution. Thereby the commonly used mosaic parameterization of subgrid runoff ratio was integrated into a statistical–dynamic scheme with the bulk heterogeneity of a grid area included. Furthermore, a series of numerical experiments evaluating the reliability of the parameterization were conducted using the data generated by the emulated simulation method. All the experimental results demonstrate that the proposed scheme is feasible and practical.展开更多
The Geodynamics-Earth-Tides-meeting-2016 was held in the Karst, the origin of geologic karst- formation. Surface-rivers are absent, and water flows in channels over distances of 30 km, forming subsurface caves. Geodet...The Geodynamics-Earth-Tides-meeting-2016 was held in the Karst, the origin of geologic karst- formation. Surface-rivers are absent, and water flows in channels over distances of 30 km, forming subsurface caves. Geodetic observations allow detecting caves and sense hydrologic flow. The Karst water had been recognized before Romans as provision for man and livestock. Proto-historic remains near the mouth of the underground river suggest the water outpouring from the Karst was associated with deities to be worshiped. Here the geodetic and cultural aspects of the Karst are summarized, illustrating the field trip that had been offered to the participants.展开更多
Carbon emissions and water use are two major kinds of human activities. To reveal whether these two activities can modify the hydrological cycle and climate system in China, we conducted two sets of numerical experime...Carbon emissions and water use are two major kinds of human activities. To reveal whether these two activities can modify the hydrological cycle and climate system in China, we conducted two sets of numerical experiments using regional climate model RegCM4. In the first experiment used to study the climatic responses to human carbon emissions, the model were configured over entire China because the impacts of carbon emissions can be detected across the whole country. Results from the first experiment revealed that near-surface air temperature may significantly increase from 2007 to 2059 at a rate exceeding 0.1 ~C per decade in most areas across the country; southwestern and southeastern China also showed increasing trends in summer precipitation, with rates exceeding 10 mm per decade over the same period. In summer, only northern China showed an increasing trend of evapotranspiration, with increase rates ranging from 1 to 5 mm per decade; in winter, increase rates ranging from 1 to 5 mm per decade were observed in most regions. These effects are believed to be caused by global warming from human carbon emissions. In the second experiment used to study the effects of human water use, the model were configured over a limited region-- Haihe River Basin in the northern China, because compared with the human carbon emissions, the effects of human water use are much more local and regional, and the Haihe River Basin is the most typical region in China that suffers from both intensive human groundwater exploitation and surface water diversion. We incorporated a scheme of human water regulation into RegCM4 and conducted the second experiment. Model outputs showed that the groundwater table severely declined by -10 m in 1971-2000 through human groundwater over- exploitation in the basin; in fact, current conditions are so extreme that even reducing the pumping rate by half cannot eliminate the ground- water depletion cones observed in the area. Other hydrological and climatic elements, such as soil moisture, runoff generation, air humidity, precipitation, wind field, and soil and air temperature, were also significantly affected by anthropogenic water withdrawal and consumption, although these effects could be mitigated by reducing the amount of water drawn for extraction and application.展开更多
Although forests play important roles in the hydrological cycle,there is little information that relates the water retention capacity of litter in areas under passive restoration,especially in Cerrado savannas.This st...Although forests play important roles in the hydrological cycle,there is little information that relates the water retention capacity of litter in areas under passive restoration,especially in Cerrado savannas.This study relates litter levels to water holding capacity and effective water retention among forest fragments under different passive restoration stages:46,11,and 8 years to better understand litter hydrological functions in the Cerrado.Water retention capacity and effective water retention capacity of litters(unstructured materials,branches and leaves)in the field were monitored on a monthly basis.Total litter accumulation at 46 years was significantly higher than that of the other succession stages.Unstructured litter mass was significantly higher than that of leaves and branches.The 46-year stage had the highest water holding capacity in the leaf fraction,followed by unstructured material and branches.Although the water holding capacity was lower in the oldest resto-ration,this site showed the highest efficiency under field conditions.The process was quickly reestablished,as the 11-year restoration showed results closer to that for the 46-year stage in comparison to the area at 8 years.Thus,passive restoration plays a key role in soil water mainte-nance due to the influence of litter in Cerrado savannas.Deforestation and the imminent need of restoring degraded sites,highlight the need for further studies focused on bet-ter understanding of the process of forest restoration and its temporal effect on soil water recovery dynamics.展开更多
Fire is quite a common natural phenomenon closely related to forest hydrology in forest ecosystem. The influence of fire on water is indirectly manifested in that the post fire changes of vegetation, ground cover, soi...Fire is quite a common natural phenomenon closely related to forest hydrology in forest ecosystem. The influence of fire on water is indirectly manifested in that the post fire changes of vegetation, ground cover, soil and environment affect water cycle, water quality and aquatic lives. The effect varies depending upon fire severity and frequency. Light wildland fires or prescribed burnings do not affect hydrology regime significantly but frequent burnings or intense fires can cause changes in hydrology regime similar to that caused clear cutting.展开更多
The hydrology of the Little Ruaha River which is a major catchment of the Ihemi Cluster in the Southern Agricultural Growth Corridor of Tanzania (SA-GCOT) has been studied. The study focused on the hydrological assess...The hydrology of the Little Ruaha River which is a major catchment of the Ihemi Cluster in the Southern Agricultural Growth Corridor of Tanzania (SA-GCOT) has been studied. The study focused on the hydrological assessment through analysis of the available data and developing a model that could be used for assessing impacts of environmental change. Pressures on land and water resources in the watershed are increasing mainly as a result of human activities, and understanding the hydrological regime is deemed necessary. In this study, modeling was conducted using the Soil and Water Assessment Tool (SWAT) in which meteorological and streamflow data were used in the simulation, calibration and evaluation. Calibration and evaluation was done at three gauging stations and the results were deemed plausible with NSE ranging between 0.64 and 0.80 for the two stages. The simulated flows were used for gap filling the missing data and generation of complete daily time series of streamflow at three gauging stations of Makalala, Ihimbu and Mawande. Results of statistical trends and flow duration curves, revealed decline in magnitudes of seasonal and annual flows indicating that streamflows are changing with time and may have implications on envisioned development and the water dependent ecosystems.展开更多
Global warming has become one of important environmental issues, and will alter the spatial distribution of hydrology and water re- sources through accelerating atmospheric and hydrological cycles. Yangtze River Delta...Global warming has become one of important environmental issues, and will alter the spatial distribution of hydrology and water re- sources through accelerating atmospheric and hydrological cycles. Yangtze River Delta region, an economic center in China, has experienced a re- gional temperature increase since the 1960s, forming a heat island, and the warming rate has improved since the 1990s. The characteristics of hy- drology and water resources changed under regional climate warming. Here, the impacts of climate change on hydrology and water resources were discussed from the aspects of precipitation change, sea level rise, seawater invasion and water pollution in Yangtze River Delta region, China.展开更多
Seagull Lake is an unusual saline lake,having a marine spring connected to a large continental ecosystem.With climate change the balance between marine,meteoric and groundwater inputs to,and evaporitic and groundwater
Climate change is one of the greatest issues for human society. The objective of this study is to assess the impacts of future climate change on seasonal average discharge and monthly water budget in a small headwater...Climate change is one of the greatest issues for human society. The objective of this study is to assess the impacts of future climate change on seasonal average discharge and monthly water budget in a small headwater catchment, located on the Grande River basin, in Minas Gerais, Brazil. The assessment is carried out using the hydrology model, DHSVM. The atmospheric forcing to drive the Distributed Hydrology-Soil-Vegetation Model (DHSVM) is derived from the downscaling of the HadGEM2-ES projections by the Eta Regional Climate Model, at 5-km high resolution. The projections assume the RCP4.5 and RCP8.5 IPCC AR5 emission scenarios. Baseline period was taken between 1961 and 1990. The projections are assessed in three time slices (2011-2040, 2041-2070 and 2071-2099). The climate change is assessed in time slices of 30 years and in comparison against the baseline period to evaluate the hydrological changes in the catchment. The results showed differences in the hydrological behavior between the emission scenarios and though time slices. Reductions in the magnitude of the seasonal average discharge and monthly water budget may alter the water availability. Under the RCP4.5 scenario, results show greater reductions in the water availability in the first time slice, whereas under RCP8.5 scenario greater reductions are indicated in the third time slice.展开更多
Urban development generally leads to an increase in impervious cover resulting in a greater volume of surface runoff following storm activity. However, the type of urban development in place strongly controls the degr...Urban development generally leads to an increase in impervious cover resulting in a greater volume of surface runoff following storm activity. However, the type of urban development in place strongly controls the degree of impervious cover generated. Traditional neighborhood designs focus on a medium-to-low urban density spread over larger areas, while new urbanist neighborhood designs incorporate more diversity by increasing urban density across smaller areas. The purpose of this study is to model and compare the potential surface runoff for two urban neighborhoods in Austin, Texas-Circle C Ranch, a traditional neighborhood design, and Mueller, a new urbanist development for a 10-year 24-hour storm scenario. Potential surface runoff was calculated by layering various geospatial datasets representing the physical characteristics of both study sites within the Watershed Modeling System (WMS) to configure the HEC-HMS runoff model. Results initially imply that the higher density new urbanist neighborhood significantly increases total and peak storm runoff compared to the traditional neighborhood. However, a greater number of residential units are available at Mueller over the same area as Circle C Ranch. When taking this into account the increased potential surface runoff is negated at the new urbanist site. Although new urbanist neighborhoods will usually contain more residential units than traditional developments when compared at the same scale, the higher urban density associated with these neighborhoods demand the development of more effective stormwater retention systems to cope with a potential increase in surface runoff.展开更多
Crack orientations are an important soil physical property that affects water flow, particularly in vertic soils. However, the spatial and temporal variability of crack orientations across different land uses and gilg...Crack orientations are an important soil physical property that affects water flow, particularly in vertic soils. However, the spatial and temporal variability of crack orientations across different land uses and gilgai features is not well-documented and addressed in hydrology models. Thus;there is a need to quantify crack orientations for different land uses and to incorporate their spatial and temporal dynamics into hydrological models. Our objectives were to document the spatial variability of cracks orientations across two land uses and to demonstrate the potential importance of crack orientation related to the hydrology of Vertisols. The exploratory field measurements of the spatial distribution of crack orientations across two Vertisol catenae of two land uses and gilgai features are presented. The field survey showed the complexity of crack geometry in a field, the potential impact of crack orientation on Vertisol hydrology and the challenges associated with measurement of crack orientations.展开更多
System of villagers autonomy is one of the basic political systems in China and one of those systems ensuring that the people are the masters of the country. Northwest minorities generally live in the remote northwest...System of villagers autonomy is one of the basic political systems in China and one of those systems ensuring that the people are the masters of the country. Northwest minorities generally live in the remote northwestern China where economy and education are relatively underdeveloped compared with those in central and eastern China and civil authority has great influence on rural grass-roots democracy as well as social autonomy there,which causes difficulties to the development of rural democracy and social autonomy. Assisting northwest minority regions in overcoming the difficulties of developing grass-roots democracy and social autonomy,carrying out effective measures to properly guide the development and influence of civil authority and finally achieving the construction of new socialist countryside have great significance in ensuring that people there are the masters of their country.展开更多
基金supported by the Key Research Program of Frontier Sciences,CAS(Grant No.ZDBS-LY-DQC026).
文摘Due to the great influences of both climate warming and human activities,permafrost on the Qinghai-Xizang Plateau(QXP) has been undergoing considerable degradation.Continuous degradation of plateau permafrost dramatically modifies the regional water cycle and hydrological processes,affecting the hydrogeological conditions,and ground hydrothermal status in cold regions.Permafrost thawing impacts the ecological environment,engineering facilities,and carbon storage functions,releasing some major greenhouse gases and exacerbating climate change.Despite the utilization of advanced research methodologies to investigate the changing hydrological processes and the corresponding influencing factors in permafrost regions,there still exist knowledge gaps in multivariate data,quantitative analysis of permafrost degradation's impact on various water bodies,and systematic hydrological modeling on the QXP.This review summarizes the main research methods in permafrost hydrology and elaborates on the impacts of permafrost degradation on regional precipitation distribution patterns,changes in surface runoff,expansion of thermokarst lakes/ponds,and groundwater dynamics on the QXP.Then,we discuss the current inadequacies and future research priorities,including multiple methods,observation data,and spatial and temporal scales,to provide a reference for a comprehensive analysis of the hydrological and environmental effects of permafrost degradation on the QXP under a warming climate.
文摘The conceptions of theorems, laws and corollaries of hydrology were put forward. Combining with hydrology practice, several theo- rems, laws as well as corollaries of hydrology were summarized. The study provided some references for accelerating the development of hydrology theory in these aspects and promoting the improvement of its production technology.
基金supported by the National Natural Science Foundation of China (Grant No. 41130639)
文摘The complexities of hydrological phenomena, the causes that lead to these complexities, and the essences and defects of reductionism are analyzed. The driving forces for the development of hydrology and the formation of branch subjects of hydrology are discussed. The theoretical basis and limitations of existing hydrology are summarized. Existing misunderstandings in the development of the watershed hydrological model are put forward. Finally, the necessity of the expansion of hydrology from linear to nonlinear is discussed.
基金National Natural Science Foundation of China, No.40671014Knowledge Innovation Project of the Chinese Academy of Sciences, No.KZCX2-YW-127+1 种基金Open Foundation of Key Laboratory of Oasis Ecology and De-sert Environment, CAS, No.200901-07Doctor Research Foundation of Xinjiang University, No.BS080131
文摘Based on the surface runoff, temperature and precipitation data over the last 50 years from eight representative rivers in Xinjiang, using Mann-Kendall trend and jump detection method, the paper investigated the long-term trend and jump point of time series, the surface runoff, mean annual temperature and annual precipitation. Meanwhile, the paper analyzed the relationship between runoff and temperature and precipitation, and the flood frequency and peak flow. Results showed that climate of all parts of Xinjiang conformably has experienced an increase in temperature and precipitation since the mid-1980s. Northern Xinjiang was the area that changed most significantly followed by southern and eastern Xinjiang. Affected by temperature and precipitation variation, river runoff had changed both inter-annually and intra-annually. The surface runoff of most rivers has increased significantly since the early 1990s, and some of them have even witnessed the earlier spring floods, later summer floods and increasing flood peaks. The variation characteristics were closely related with the replenishment types of rivers. Flood frequency and peak flow increased all over Xinjiang. Climate warming has had an effect on the regional hydrological cycle.
文摘Wetlands, one of the most productive systems in the biosphere are a unique ecosystem. They occur in landscapes that favor the ponding or slow runoff of surface water, discharge of ground water, or both. Wetlands are not only important for maintaining plant and animal diversity, but also for balancing global carbon budget via sequestrating or releasing CO2 from/into atmosphere depending on their management. Therefore, it is imperative to understand how wetlands form and function, then we can better manage, utilize, and protect these unique ecosystems. Hydrie soils,hydrophytic vegetation, and wetland hydrology are the three main parameters of wetlands. These parameters are interrelated with each other which jointly influence the development and functions of wetland ecosystems. The objective of this paper was to report the current understanding of wetlands and provide future research directions. The paper will first focus on aspects of hydrology research in wetlands, and then shift to soil hydrosequence and wetland vegetation to better understand processes, structure, and function of wetlands, and conclude with some possible future research directions.
基金conducted with in the Nation Basic Research Program of China (973 Program, Research No. 2007CB411502)project "Matter fluxes in Inner Mongo-lia as influenced by stocking rate (MAGIM)" funded by the German Science Foundation (DFG) (Research Unit 536)
文摘The use of isotope techniques and methods in catchment hydrology in the last 50 years has generated two major types of progress: (1) Assessment of the temporal variations of the major stocks and flows of water in catchments, from which the estimation of wa-ter residence times is introduced in this paper. (2) Assessment of catchment hydrologic processes, in which the interactions be-tween different waters, hydrographical separation, and bio-geochemical process are described by using isotopes tracers. Future progress on isotope techniques and methods in hydrology is toward the understanding of the hydrological process in large river basins. Much potential also waits realization in terms of how isotope information may be used to calibrate and test distributed rainfall-runoff models and regarding aid in the quantification of sustainable water resources management.
基金This work is supported jointly by the Major-Subject Program of the National Natural Science Foundation of China (Grant No.498992
文摘An analytical expression for subgrid–scale inhomogeneous runoff ratios generated by heterogeneous soil moisture content and climatic precipitation forcing is presented based on physical mechanisms for land surface hydrology and theory of statistical probability distribution. Thereby the commonly used mosaic parameterization of subgrid runoff ratio was integrated into a statistical–dynamic scheme with the bulk heterogeneity of a grid area included. Furthermore, a series of numerical experiments evaluating the reliability of the parameterization were conducted using the data generated by the emulated simulation method. All the experimental results demonstrate that the proposed scheme is feasible and practical.
文摘The Geodynamics-Earth-Tides-meeting-2016 was held in the Karst, the origin of geologic karst- formation. Surface-rivers are absent, and water flows in channels over distances of 30 km, forming subsurface caves. Geodetic observations allow detecting caves and sense hydrologic flow. The Karst water had been recognized before Romans as provision for man and livestock. Proto-historic remains near the mouth of the underground river suggest the water outpouring from the Karst was associated with deities to be worshiped. Here the geodetic and cultural aspects of the Karst are summarized, illustrating the field trip that had been offered to the participants.
文摘Carbon emissions and water use are two major kinds of human activities. To reveal whether these two activities can modify the hydrological cycle and climate system in China, we conducted two sets of numerical experiments using regional climate model RegCM4. In the first experiment used to study the climatic responses to human carbon emissions, the model were configured over entire China because the impacts of carbon emissions can be detected across the whole country. Results from the first experiment revealed that near-surface air temperature may significantly increase from 2007 to 2059 at a rate exceeding 0.1 ~C per decade in most areas across the country; southwestern and southeastern China also showed increasing trends in summer precipitation, with rates exceeding 10 mm per decade over the same period. In summer, only northern China showed an increasing trend of evapotranspiration, with increase rates ranging from 1 to 5 mm per decade; in winter, increase rates ranging from 1 to 5 mm per decade were observed in most regions. These effects are believed to be caused by global warming from human carbon emissions. In the second experiment used to study the effects of human water use, the model were configured over a limited region-- Haihe River Basin in the northern China, because compared with the human carbon emissions, the effects of human water use are much more local and regional, and the Haihe River Basin is the most typical region in China that suffers from both intensive human groundwater exploitation and surface water diversion. We incorporated a scheme of human water regulation into RegCM4 and conducted the second experiment. Model outputs showed that the groundwater table severely declined by -10 m in 1971-2000 through human groundwater over- exploitation in the basin; in fact, current conditions are so extreme that even reducing the pumping rate by half cannot eliminate the ground- water depletion cones observed in the area. Other hydrological and climatic elements, such as soil moisture, runoff generation, air humidity, precipitation, wind field, and soil and air temperature, were also significantly affected by anthropogenic water withdrawal and consumption, although these effects could be mitigated by reducing the amount of water drawn for extraction and application.
基金This work is supported by the International Paper Co.from Brazil(Process 23112.000670/2015-59)by Brazilian National Council for Scientific and Technological Development(CNPq)in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil(CAPES)-Finance Code 001.
文摘Although forests play important roles in the hydrological cycle,there is little information that relates the water retention capacity of litter in areas under passive restoration,especially in Cerrado savannas.This study relates litter levels to water holding capacity and effective water retention among forest fragments under different passive restoration stages:46,11,and 8 years to better understand litter hydrological functions in the Cerrado.Water retention capacity and effective water retention capacity of litters(unstructured materials,branches and leaves)in the field were monitored on a monthly basis.Total litter accumulation at 46 years was significantly higher than that of the other succession stages.Unstructured litter mass was significantly higher than that of leaves and branches.The 46-year stage had the highest water holding capacity in the leaf fraction,followed by unstructured material and branches.Although the water holding capacity was lower in the oldest resto-ration,this site showed the highest efficiency under field conditions.The process was quickly reestablished,as the 11-year restoration showed results closer to that for the 46-year stage in comparison to the area at 8 years.Thus,passive restoration plays a key role in soil water mainte-nance due to the influence of litter in Cerrado savannas.Deforestation and the imminent need of restoring degraded sites,highlight the need for further studies focused on bet-ter understanding of the process of forest restoration and its temporal effect on soil water recovery dynamics.
文摘Fire is quite a common natural phenomenon closely related to forest hydrology in forest ecosystem. The influence of fire on water is indirectly manifested in that the post fire changes of vegetation, ground cover, soil and environment affect water cycle, water quality and aquatic lives. The effect varies depending upon fire severity and frequency. Light wildland fires or prescribed burnings do not affect hydrology regime significantly but frequent burnings or intense fires can cause changes in hydrology regime similar to that caused clear cutting.
文摘The hydrology of the Little Ruaha River which is a major catchment of the Ihemi Cluster in the Southern Agricultural Growth Corridor of Tanzania (SA-GCOT) has been studied. The study focused on the hydrological assessment through analysis of the available data and developing a model that could be used for assessing impacts of environmental change. Pressures on land and water resources in the watershed are increasing mainly as a result of human activities, and understanding the hydrological regime is deemed necessary. In this study, modeling was conducted using the Soil and Water Assessment Tool (SWAT) in which meteorological and streamflow data were used in the simulation, calibration and evaluation. Calibration and evaluation was done at three gauging stations and the results were deemed plausible with NSE ranging between 0.64 and 0.80 for the two stages. The simulated flows were used for gap filling the missing data and generation of complete daily time series of streamflow at three gauging stations of Makalala, Ihimbu and Mawande. Results of statistical trends and flow duration curves, revealed decline in magnitudes of seasonal and annual flows indicating that streamflows are changing with time and may have implications on envisioned development and the water dependent ecosystems.
基金Supported by Natural Science Foundation of Jiangsu Province,China (BK2011096)Survey of National Soil Situation and Pollution Control (GZTR20070302)
文摘Global warming has become one of important environmental issues, and will alter the spatial distribution of hydrology and water re- sources through accelerating atmospheric and hydrological cycles. Yangtze River Delta region, an economic center in China, has experienced a re- gional temperature increase since the 1960s, forming a heat island, and the warming rate has improved since the 1990s. The characteristics of hy- drology and water resources changed under regional climate warming. Here, the impacts of climate change on hydrology and water resources were discussed from the aspects of precipitation change, sea level rise, seawater invasion and water pollution in Yangtze River Delta region, China.
基金Financial assistance for the researchers to undertake the initial fieldwork in 2012 was provided by the Friends of Streaky Bay Parks as a Caring for our Country grantThe Royal Society of South Australia provided a research grant to assist with the continuation of the work in 2013
文摘Seagull Lake is an unusual saline lake,having a marine spring connected to a large continental ecosystem.With climate change the balance between marine,meteoric and groundwater inputs to,and evaporitic and groundwater
文摘Climate change is one of the greatest issues for human society. The objective of this study is to assess the impacts of future climate change on seasonal average discharge and monthly water budget in a small headwater catchment, located on the Grande River basin, in Minas Gerais, Brazil. The assessment is carried out using the hydrology model, DHSVM. The atmospheric forcing to drive the Distributed Hydrology-Soil-Vegetation Model (DHSVM) is derived from the downscaling of the HadGEM2-ES projections by the Eta Regional Climate Model, at 5-km high resolution. The projections assume the RCP4.5 and RCP8.5 IPCC AR5 emission scenarios. Baseline period was taken between 1961 and 1990. The projections are assessed in three time slices (2011-2040, 2041-2070 and 2071-2099). The climate change is assessed in time slices of 30 years and in comparison against the baseline period to evaluate the hydrological changes in the catchment. The results showed differences in the hydrological behavior between the emission scenarios and though time slices. Reductions in the magnitude of the seasonal average discharge and monthly water budget may alter the water availability. Under the RCP4.5 scenario, results show greater reductions in the water availability in the first time slice, whereas under RCP8.5 scenario greater reductions are indicated in the third time slice.
文摘Urban development generally leads to an increase in impervious cover resulting in a greater volume of surface runoff following storm activity. However, the type of urban development in place strongly controls the degree of impervious cover generated. Traditional neighborhood designs focus on a medium-to-low urban density spread over larger areas, while new urbanist neighborhood designs incorporate more diversity by increasing urban density across smaller areas. The purpose of this study is to model and compare the potential surface runoff for two urban neighborhoods in Austin, Texas-Circle C Ranch, a traditional neighborhood design, and Mueller, a new urbanist development for a 10-year 24-hour storm scenario. Potential surface runoff was calculated by layering various geospatial datasets representing the physical characteristics of both study sites within the Watershed Modeling System (WMS) to configure the HEC-HMS runoff model. Results initially imply that the higher density new urbanist neighborhood significantly increases total and peak storm runoff compared to the traditional neighborhood. However, a greater number of residential units are available at Mueller over the same area as Circle C Ranch. When taking this into account the increased potential surface runoff is negated at the new urbanist site. Although new urbanist neighborhoods will usually contain more residential units than traditional developments when compared at the same scale, the higher urban density associated with these neighborhoods demand the development of more effective stormwater retention systems to cope with a potential increase in surface runoff.
文摘Crack orientations are an important soil physical property that affects water flow, particularly in vertic soils. However, the spatial and temporal variability of crack orientations across different land uses and gilgai features is not well-documented and addressed in hydrology models. Thus;there is a need to quantify crack orientations for different land uses and to incorporate their spatial and temporal dynamics into hydrological models. Our objectives were to document the spatial variability of cracks orientations across two land uses and to demonstrate the potential importance of crack orientation related to the hydrology of Vertisols. The exploratory field measurements of the spatial distribution of crack orientations across two Vertisol catenae of two land uses and gilgai features are presented. The field survey showed the complexity of crack geometry in a field, the potential impact of crack orientation on Vertisol hydrology and the challenges associated with measurement of crack orientations.
基金Supported by the Social Sciences Planning Project Launched by Ministry of Education of China in 2011-Study on the Informal Institutional Implementation and the Coordinated Development between Economy and Society in the Northwest Minority Areas(11YJA710005)China Scholarship Council([2012]5030)+1 种基金Professor Andrew J.Nathan,Weatherhead East Asian Insti-tute of Columbia UniversityJames D.Seymour,Adjunct Associate Professor at Chinese University of Hong Kong
文摘System of villagers autonomy is one of the basic political systems in China and one of those systems ensuring that the people are the masters of the country. Northwest minorities generally live in the remote northwestern China where economy and education are relatively underdeveloped compared with those in central and eastern China and civil authority has great influence on rural grass-roots democracy as well as social autonomy there,which causes difficulties to the development of rural democracy and social autonomy. Assisting northwest minority regions in overcoming the difficulties of developing grass-roots democracy and social autonomy,carrying out effective measures to properly guide the development and influence of civil authority and finally achieving the construction of new socialist countryside have great significance in ensuring that people there are the masters of their country.