Vegetation cover has a major effect on water flow in soils. Two sites, separated by distance of about 50 m, were selected to quantify the influence of grass cover on hydrophysical parameters and heterogeneity of water...Vegetation cover has a major effect on water flow in soils. Two sites, separated by distance of about 50 m, were selected to quantify the influence of grass cover on hydrophysical parameters and heterogeneity of water flow in a sandy soil emerging during a heavy rain following a long hot, dry period. A control soil （pure sand） with limited impact of vegetation or organic matter was obtained by sampling at 50 cm depth beneath a glade area, and a grassland soil was covered in a 10 cm thick humic layer and colonised by grasses. The persistence of water repellency was measured using the water drop penetration time test, sorptivity and unsaturated hydraulic conductivity using a mini disk infiltrometer, and saturated hydraulic conductivity using a double-ring infiltrometer. Dye tracer experiments were used to assess the heterogeneity of water flow, and both the modified method for estimating effective cross section and an original method for assessing the degree of preferential flow were used to quantify this heterogeneity from the images of dyed soil profiles. Most hydrophysical parameters were substantially different between the two surfaces. The grassland soil had an index of water repellency about 10 times that of pure sand and the persistence of water repellency almost 350 times that of pure sand. Water and ethanol sorptivities in the grassland soil were 7% and 43%, respectively, of those of the pure sand. Hydraulic conductivity and saturated hydraulic conductivities in the grassland soil were 5% and 16% of those of the pure sand, respectively. Dye tracer experiments revealed a stable flow with ＂air-draining＂ condition in pure sand and well-developed preferential flow in grassland soil, corresponding to individual grass tussocks and sinai! micro-depressions. The grassland soil was substantially more water repellent and had 3 times the degree of preferential flow compared to pure sand. The results of this study reinforce our view that the consequences of any change in climate, which will ultimately influence hydrology, will be markedly different between grasslands and bare soils.展开更多
Large dams are complex structures with nonlinear dynamic behavior.Engineers often are forced to assess dam safety based on the available incomplete data,which is extremely difficult.This important problem can be solve...Large dams are complex structures with nonlinear dynamic behavior.Engineers often are forced to assess dam safety based on the available incomplete data,which is extremely difficult.This important problem can be solved with the modern theory of complex systems.It is possible to derive characteristics of the whole unknown dynamics of a structure using few data sets of certain carefully selected representative parameter(s).By means of high quality continuous records of some geotechnical characteristic(s)of a dam and modern methods of time series linear/nonlinear analysis the main dynamical features of the entire,unknown process(here—dam deformation)can be analyzed.We created the cost-effective Monitoring Telemetric System for Dam Diagnostics(DAMWATCH),which consists of sensors(tiltmeters),terminal and central controllers connected by the GSM/GPRS Modem to the diagnostic center.The tilt data recorded for varying reservoir level are compared with static design model of dam deformations computed by a finite element method(FEM)for the dam-reservoir-foundation system.Besides,recently developed linear/nonlinear data analysis and prediction schemes may help to quantify fine dynamical features of the dam behavior.The software package DAMTOOL has been developed for this purpose.The differences between measured and theoretically predicted response parameters of the dam may signal abnormal behavior of the object.The data obtained already by testing of the DAMWATCH/DAMTOOL system during operation of the high Enguri arc dam and reservoir(Georgia)show interesting long-term and short-term patterns of tilts in the dam body,which can be used for dam diagnostics.The proposed real-time telemetric monitoring(DAMWATCH)complex and linear/nonlinear dynamical analysis system(DAMTOOL)are unique.展开更多
基金Supported by the Slovak Scientific Grant Agency VEGA(Nos.2/0042/11 and 2/0073/11)the Ministry of the Environment of the Czech Republic(No.VaV SP/lab/151/07)
文摘Vegetation cover has a major effect on water flow in soils. Two sites, separated by distance of about 50 m, were selected to quantify the influence of grass cover on hydrophysical parameters and heterogeneity of water flow in a sandy soil emerging during a heavy rain following a long hot, dry period. A control soil （pure sand） with limited impact of vegetation or organic matter was obtained by sampling at 50 cm depth beneath a glade area, and a grassland soil was covered in a 10 cm thick humic layer and colonised by grasses. The persistence of water repellency was measured using the water drop penetration time test, sorptivity and unsaturated hydraulic conductivity using a mini disk infiltrometer, and saturated hydraulic conductivity using a double-ring infiltrometer. Dye tracer experiments were used to assess the heterogeneity of water flow, and both the modified method for estimating effective cross section and an original method for assessing the degree of preferential flow were used to quantify this heterogeneity from the images of dyed soil profiles. Most hydrophysical parameters were substantially different between the two surfaces. The grassland soil had an index of water repellency about 10 times that of pure sand and the persistence of water repellency almost 350 times that of pure sand. Water and ethanol sorptivities in the grassland soil were 7% and 43%, respectively, of those of the pure sand. Hydraulic conductivity and saturated hydraulic conductivities in the grassland soil were 5% and 16% of those of the pure sand, respectively. Dye tracer experiments revealed a stable flow with ＂air-draining＂ condition in pure sand and well-developed preferential flow in grassland soil, corresponding to individual grass tussocks and sinai! micro-depressions. The grassland soil was substantially more water repellent and had 3 times the degree of preferential flow compared to pure sand. The results of this study reinforce our view that the consequences of any change in climate, which will ultimately influence hydrology, will be markedly different between grasslands and bare soils.
基金the financial support of joint project(#5016)of Georgian National Scientific Foundation(GNSF)and ScienceTechnology Center of Ukraine(STCU)and Open Partial Agreement on the Major Disasters at the Council of Europe(EUR-OPA).
文摘Large dams are complex structures with nonlinear dynamic behavior.Engineers often are forced to assess dam safety based on the available incomplete data,which is extremely difficult.This important problem can be solved with the modern theory of complex systems.It is possible to derive characteristics of the whole unknown dynamics of a structure using few data sets of certain carefully selected representative parameter(s).By means of high quality continuous records of some geotechnical characteristic(s)of a dam and modern methods of time series linear/nonlinear analysis the main dynamical features of the entire,unknown process(here—dam deformation)can be analyzed.We created the cost-effective Monitoring Telemetric System for Dam Diagnostics(DAMWATCH),which consists of sensors(tiltmeters),terminal and central controllers connected by the GSM/GPRS Modem to the diagnostic center.The tilt data recorded for varying reservoir level are compared with static design model of dam deformations computed by a finite element method(FEM)for the dam-reservoir-foundation system.Besides,recently developed linear/nonlinear data analysis and prediction schemes may help to quantify fine dynamical features of the dam behavior.The software package DAMTOOL has been developed for this purpose.The differences between measured and theoretically predicted response parameters of the dam may signal abnormal behavior of the object.The data obtained already by testing of the DAMWATCH/DAMTOOL system during operation of the high Enguri arc dam and reservoir(Georgia)show interesting long-term and short-term patterns of tilts in the dam body,which can be used for dam diagnostics.The proposed real-time telemetric monitoring(DAMWATCH)complex and linear/nonlinear dynamical analysis system(DAMTOOL)are unique.
