In the Elkhorn River,burrows,tubes,and sediment mounds created by invertebrate bioturbation were observed in the exposed streambed and commonly concentrated on the fine-sediment patches,which consist of silt,clay,and ...In the Elkhorn River,burrows,tubes,and sediment mounds created by invertebrate bioturbation were observed in the exposed streambed and commonly concentrated on the fine-sediment patches,which consist of silt,clay,and organic matter.These invertebrate activities could loosen the thin layer of clogging sediments and result in an increase of pore size in the sediments,leading to greater vertical hydraulic conductivity of the streambed(Kv).The measurements of the vertical hydraulic gradient across the submerged streambed show that vertical flux in the hyporheic zone can alter directions(upward versus downward)for two locations only a few meters apart.In situ permeameter tests show that streambed Kv in the upper sediment layer is much higher than that in the lower sediment layer,and the calculated Kv in the submerged streambed is consistently greater than that in the clogged sediments around the shorelines of the sand bars.Moreover,a phenomenon of gas bubble release at the water-sediment interface from the subsurface sediments was observed in the groundwater seepage zone where flow velocity is extremely small.The bursting of gas bubbles can potentially break the thin clogging layer of sediments and enhance the vertical hydraulic conductivity of the streambed.展开更多
Flood routing models are critical to flood forecasting and confluence calculations. In the streams that dry up and disconnect from groundwater, the streambed infiltration is intensive and has a significant effect on f...Flood routing models are critical to flood forecasting and confluence calculations. In the streams that dry up and disconnect from groundwater, the streambed infiltration is intensive and has a significant effect on flood wave movement. Streambed infiltration should be considered in flood routing. A flood routing model incorporating intensive streambed infiltration is proposed. In the model a streambed infiltration simulation method based on soil infiltration theory is developed. In this method the Horton equation is used to calculate infiltration capacity. A trial-and-error method is developed to calculate infiltration rate and determine whether the flood wave can travel downstream. A formula is derived to calculate infiltration flow per unit length. The Muskingum-Cunge method with streambed infiltration flow as lateral outflow is used for flood routing. The proposed model is applied to the stream from the downstream of the Yuecheng Reservoir to the Caixiaozhuang Hydrometric Station in the Zhangwei River of the Haihe River Basin. Simulation results show that the accuracy of the model is high, and the infiltration simulation method can represent infiltration processes well. The proposed model is simple and practical for flood simulation and forecasting, and can be used in river confluence calculations in a rainfall-runoff model for arid and semiarid regions.展开更多
The vertical seepage velocity is an important parameter in the groundwater-surface water （GW-SW） exchange process. It is reported that the periodical fluctuated temperature record of the streambed can be used to det...The vertical seepage velocity is an important parameter in the groundwater-surface water （GW-SW） exchange process. It is reported that the periodical fluctuated temperature record of the streambed can be used to determine the seepage velocity. Based on a 1-D flow and heat transport model with a sinusoidal temperature oscillation at the upstream boundary, a new analytical model is built. This analytical model can be used to determine the seepage velocity from the amplitude ratio of the deep and shallow test points. The process of calculation is discussed. The field data are superimposed by multi-periods, so the spectrum analysis and the data filtering are desirable. For the typical seepage medium, the analytical model is effective to compute the seepage velocity between -2 m/d and 6 m/d by using the record of the daily period fluctuation. The temperature time-series analytical model is used to determine the upwards seepage under the condition that the spacing of test points is small （less than 0.2 m）. Lastly, a case study for the Russian River shows that this model is very convenient to determine the temporal changes of the GW-SW exchange.展开更多
基金the Program for Changjiang Scholars and Innovative Research Team of China Ministry of Education(No.IRT0811).
文摘In the Elkhorn River,burrows,tubes,and sediment mounds created by invertebrate bioturbation were observed in the exposed streambed and commonly concentrated on the fine-sediment patches,which consist of silt,clay,and organic matter.These invertebrate activities could loosen the thin layer of clogging sediments and result in an increase of pore size in the sediments,leading to greater vertical hydraulic conductivity of the streambed(Kv).The measurements of the vertical hydraulic gradient across the submerged streambed show that vertical flux in the hyporheic zone can alter directions(upward versus downward)for two locations only a few meters apart.In situ permeameter tests show that streambed Kv in the upper sediment layer is much higher than that in the lower sediment layer,and the calculated Kv in the submerged streambed is consistently greater than that in the clogged sediments around the shorelines of the sand bars.Moreover,a phenomenon of gas bubble release at the water-sediment interface from the subsurface sediments was observed in the groundwater seepage zone where flow velocity is extremely small.The bursting of gas bubbles can potentially break the thin clogging layer of sediments and enhance the vertical hydraulic conductivity of the streambed.
基金supported by the National Natural Science Foundation of China(Grant Nos.51279223,51109055,51409169,51309004,51409141)the Public Welfare Industry Funding for Research and Special Projects of Ministry of Water Resources of China(Grant Nos.201001074,201201022)the Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering(Grant No.2013491011)
文摘Flood routing models are critical to flood forecasting and confluence calculations. In the streams that dry up and disconnect from groundwater, the streambed infiltration is intensive and has a significant effect on flood wave movement. Streambed infiltration should be considered in flood routing. A flood routing model incorporating intensive streambed infiltration is proposed. In the model a streambed infiltration simulation method based on soil infiltration theory is developed. In this method the Horton equation is used to calculate infiltration capacity. A trial-and-error method is developed to calculate infiltration rate and determine whether the flood wave can travel downstream. A formula is derived to calculate infiltration flow per unit length. The Muskingum-Cunge method with streambed infiltration flow as lateral outflow is used for flood routing. The proposed model is applied to the stream from the downstream of the Yuecheng Reservoir to the Caixiaozhuang Hydrometric Station in the Zhangwei River of the Haihe River Basin. Simulation results show that the accuracy of the model is high, and the infiltration simulation method can represent infiltration processes well. The proposed model is simple and practical for flood simulation and forecasting, and can be used in river confluence calculations in a rainfall-runoff model for arid and semiarid regions.
基金supported by the National Natural Science Foundation of China (Grant No. 41272265)the Scientific Research and innovate Foundation to support college graduate of Jiangsu Province (Grant No. CX09B_167Z)
文摘The vertical seepage velocity is an important parameter in the groundwater-surface water （GW-SW） exchange process. It is reported that the periodical fluctuated temperature record of the streambed can be used to determine the seepage velocity. Based on a 1-D flow and heat transport model with a sinusoidal temperature oscillation at the upstream boundary, a new analytical model is built. This analytical model can be used to determine the seepage velocity from the amplitude ratio of the deep and shallow test points. The process of calculation is discussed. The field data are superimposed by multi-periods, so the spectrum analysis and the data filtering are desirable. For the typical seepage medium, the analytical model is effective to compute the seepage velocity between -2 m/d and 6 m/d by using the record of the daily period fluctuation. The temperature time-series analytical model is used to determine the upwards seepage under the condition that the spacing of test points is small （less than 0.2 m）. Lastly, a case study for the Russian River shows that this model is very convenient to determine the temporal changes of the GW-SW exchange.
