To evaluate isotopic tracers at natural abundances by providing basic isotope data of the hydrological investigations and assessing the impacts of different factors on the water cycle, a total of 197 water samples wer...To evaluate isotopic tracers at natural abundances by providing basic isotope data of the hydrological investigations and assessing the impacts of different factors on the water cycle, a total of 197 water samples were collected from the Laohugou Glacial catchment in the Shule River basin northwestern China during the 2013 ablation seasons and analyzed their H- and O-isotope composition. The results showed that the isotopic composition of precipitation in the Qilianshan Station in the Laohugou Glacial catchment was remarkable variability. Correspondingly, a higher slope of δ180-δD diagram, with an average of 8.74, is obtained based on the precipitation samples collected on the Glacier No.la, mainly attributed to the lower temperature on the glacier surface. Because of percolation and elution, the bottom of the firn the isotopic composition at is nearly steady. The 6180 /altitude gradients for precipitation and melt water were -o.37%o/100 m and -o.34%o/100 m, respectively Exposed to the air and influenced by strong ablation and evaporation, the isotopic values and the 6180 vs 6D diagram of the glacial surface ice show no altitudinal effect, indicating that glacier ice has the similar origins with the firn. The variation of isotopic composition in the melt water, varying from -l0.7‰ to -16.9‰ （8180） and from -61.1%o to -122.1%o （6D） indicates the recharging of snowmelt and glacial ice melt water produced at different altitudes. With a mean value of -13.3‰ for 8180 and -89.7‰ for 8D, the isotopic composition of the stream water is much closer to the melt water, indicating that stream water is mainly recharged by the ablation water. Our results of the stable isotopic compositions in natural water in the Laohugou Glacial catchment indicate the fractionations and the smoothing fluctuations of the stable isotopes during evaporation, infiltration and mixture.展开更多
The borders of Illinois were established when Illinois became a state in 1818. The western border was delineated using the Mississippi River, and the Ohio River was used as the southern border. The eastern border was ...The borders of Illinois were established when Illinois became a state in 1818. The western border was delineated using the Mississippi River, and the Ohio River was used as the southern border. The eastern border was formed by the Ohio and Wabash Rivers plus the line along latitude 42030＇30＇＇ connecting the Wabash River to Lake Michigan. As initially proposed, the northern border of Illinois would have been 82 km （51 mi） to the south of the current longitude line of 87~31 ＇. This 2,160,000 ha （5,440,000 ac） addition to Illinois resulted in the territory having the required minimum of 40,000 people to qualify as a state. The northern border was moved to allow the linkage of the Great Lakes shipping route to the Illinois and Mississippi River navigation channels. Illinois thus gained a valuable shoreline on Lake Michigan and a location for a shipping port hub which became Chicago. Initially the transfer of goods between these waterways required a portage, but later a shipping canal was created to link the waterways. During the Civil War, Union forces used the connected waterway systems as a northern supply route to avoid the contested Ohio River.展开更多
Reconstruction of natural streamflow is fundamental to the sustainable management of water resources.In China,previous reconstructions from sparse and poor-quality gauge measurements have led to large biases in simula...Reconstruction of natural streamflow is fundamental to the sustainable management of water resources.In China,previous reconstructions from sparse and poor-quality gauge measurements have led to large biases in simulation of the interannual and seasonal variability of natural flows.Here we use a well-trained and tested land surface model coupled to a routing model with flow direction correction to reconstruct the first high-quality gauge-based natural streamflow dataset for China,covering all its330 catchments during the period from 1961 to 2018.A stronger positive linear relationship holds between upstream routing cells and drainage areas,after flow direction correction to 330 catchments.We also introduce a parameter-uncertainty analysis framework including sensitivity analysis,optimization,and regionalization,which further minimizes biases between modeled and inferred natural streamflow from natural or near-natural gauges.The resulting behavior of the natural hydrological system is represented properly by the model which achieves high skill metric values of the monthly streamflow,with about 83%of the 330 catchments having Nash-Sutcliffe efficiency coefficient(NSE)>0.7,and about56%of the 330 catchments having Kling-Gupta efficiency coefficient(KGE)>0.7.The proposed construction scheme has important implications for similar simulation studies in other regions,and the developed low bias long-term national datasets by statistical postprocessing should be useful in supporting river management activities in China.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
基金the projects of National Major Scientific Research Project (2013CBA01806)National Natural Science Foundation of China (Grant Nos. 41271085,41130641)open fund project of State Key Laboratory of Cryospheric Science (SKLCS-OP2013-05)
文摘To evaluate isotopic tracers at natural abundances by providing basic isotope data of the hydrological investigations and assessing the impacts of different factors on the water cycle, a total of 197 water samples were collected from the Laohugou Glacial catchment in the Shule River basin northwestern China during the 2013 ablation seasons and analyzed their H- and O-isotope composition. The results showed that the isotopic composition of precipitation in the Qilianshan Station in the Laohugou Glacial catchment was remarkable variability. Correspondingly, a higher slope of δ180-δD diagram, with an average of 8.74, is obtained based on the precipitation samples collected on the Glacier No.la, mainly attributed to the lower temperature on the glacier surface. Because of percolation and elution, the bottom of the firn the isotopic composition at is nearly steady. The 6180 /altitude gradients for precipitation and melt water were -o.37%o/100 m and -o.34%o/100 m, respectively Exposed to the air and influenced by strong ablation and evaporation, the isotopic values and the 6180 vs 6D diagram of the glacial surface ice show no altitudinal effect, indicating that glacier ice has the similar origins with the firn. The variation of isotopic composition in the melt water, varying from -l0.7‰ to -16.9‰ （8180） and from -61.1%o to -122.1%o （6D） indicates the recharging of snowmelt and glacial ice melt water produced at different altitudes. With a mean value of -13.3‰ for 8180 and -89.7‰ for 8D, the isotopic composition of the stream water is much closer to the melt water, indicating that stream water is mainly recharged by the ablation water. Our results of the stable isotopic compositions in natural water in the Laohugou Glacial catchment indicate the fractionations and the smoothing fluctuations of the stable isotopes during evaporation, infiltration and mixture.
文摘The borders of Illinois were established when Illinois became a state in 1818. The western border was delineated using the Mississippi River, and the Ohio River was used as the southern border. The eastern border was formed by the Ohio and Wabash Rivers plus the line along latitude 42030＇30＇＇ connecting the Wabash River to Lake Michigan. As initially proposed, the northern border of Illinois would have been 82 km （51 mi） to the south of the current longitude line of 87~31 ＇. This 2,160,000 ha （5,440,000 ac） addition to Illinois resulted in the territory having the required minimum of 40,000 people to qualify as a state. The northern border was moved to allow the linkage of the Great Lakes shipping route to the Illinois and Mississippi River navigation channels. Illinois thus gained a valuable shoreline on Lake Michigan and a location for a shipping port hub which became Chicago. Initially the transfer of goods between these waterways required a portage, but later a shipping canal was created to link the waterways. During the Civil War, Union forces used the connected waterway systems as a northern supply route to avoid the contested Ohio River.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0405)the National Natural Science Foundation of China(42041006,41877155)+1 种基金support from the Center for Geodata and Analysis,Faculty of Geographical Science,Beijing Normal University(https://gda.bnu.edu.cn/)reviewed by Ministry of Natural Resources of the People’s Republic of China(GS(2021)7303)。
文摘Reconstruction of natural streamflow is fundamental to the sustainable management of water resources.In China,previous reconstructions from sparse and poor-quality gauge measurements have led to large biases in simulation of the interannual and seasonal variability of natural flows.Here we use a well-trained and tested land surface model coupled to a routing model with flow direction correction to reconstruct the first high-quality gauge-based natural streamflow dataset for China,covering all its330 catchments during the period from 1961 to 2018.A stronger positive linear relationship holds between upstream routing cells and drainage areas,after flow direction correction to 330 catchments.We also introduce a parameter-uncertainty analysis framework including sensitivity analysis,optimization,and regionalization,which further minimizes biases between modeled and inferred natural streamflow from natural or near-natural gauges.The resulting behavior of the natural hydrological system is represented properly by the model which achieves high skill metric values of the monthly streamflow,with about 83%of the 330 catchments having Nash-Sutcliffe efficiency coefficient(NSE)>0.7,and about56%of the 330 catchments having Kling-Gupta efficiency coefficient(KGE)>0.7.The proposed construction scheme has important implications for similar simulation studies in other regions,and the developed low bias long-term national datasets by statistical postprocessing should be useful in supporting river management activities in China.
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.
