A knowledge of soil permeability is essential to evaluate hydrologic characteristics of soil, such as water storage and water movement, and soil permeability coefficient is an important parameter that reflects soil pe...A knowledge of soil permeability is essential to evaluate hydrologic characteristics of soil, such as water storage and water movement, and soil permeability coefficient is an important parameter that reflects soil permeability. In order to confirm the acceptability of the one-dimensional horizontal infiltration method（one-D method） for simultaneously determining both the saturated and unsaturated permeability coefficients of loamy sand, we first measured the cumulative infiltration and the wetting front distance under various infiltration heads through a series of one-dimensional horizontal infiltration experiments, and then analyzed the relationships of the cumulative horizontal infiltration with the wetting front distance and the square root of infiltration time. We finally compared the permeability results from Gardner model based on the one-D method with the results from other two commonly-used methods（i.e., constant head method and van Genuchten model） to evaluate the acceptability and applicability of the one-D method. The results showed that there was a robust linear relationship between the cumulative horizontal infiltration and the wetting front distance, suggesting that it is more appropriate to take the soil moisture content after infiltration in the entire wetted zone as the average soil moisture content than as the saturated soil moisture content. The results also showed that there was a robust linear relationship between the cumulative horizontal infiltration and the square root of infiltration time, suggesting that the Philip infiltration formula can better reflect the characteristics of cumulative horizontal infiltration under different infiltration heads. The following two facts indicate that it is feasible to use the one-D method for simultaneously determining the saturated and unsaturated permeability coefficients of loamy sand. First, the saturated permeability coefficient（prescribed in the Gardner model） of loamy sand obtained from the one-D method well agreed with the value obtained from the constant head method. Second, the relationship of unsaturated permeability coefficient with soil water suction for loamy sand calculated using Gardner model based on the one-D method was nearly identical with the same relationship calculated using van Genuchten model.展开更多
Infiltration–runoff–slope instability mechanism of macropore slope under heavy rainfall is unclear.This paper studied its instability mechanism with an improved Green–Ampt(GA)model considering the dual-porosity(i.e...Infiltration–runoff–slope instability mechanism of macropore slope under heavy rainfall is unclear.This paper studied its instability mechanism with an improved Green–Ampt(GA)model considering the dual-porosity(i.e.,matrix and macropore)and ponding condition,and proposed the infiltration equations,infiltration–runoff coupled model,and safety factor calculation method.Results show that the infiltration processes of macropore slope can be divided into three stages,and the proposed model is rational by a comparative analysis.The wetting front depth of the traditional unsaturated slope is 17.2%larger than that of the macropore slope in the early rainfall stage and 27%smaller than that of the macropore slope in the late rainfall stage.Then,macropores benefit the slope stability in the early rainfall but not in the latter.Macropore flow does not occur initially but becomes pronounced with increasing rainfall duration.The equal depth of the wetting front in the two domains is regarded as the onset criteria of macropore flow.Parameter analysis shows that macropore flow is delayed by increasing proportion of macropore domain(ω_(f)),whereas promoted by increasing ratio of saturated permeability coefficients between the two domains(μ).The increasing trend of ponding depth is sharp at first and then grows slowly.Finally,when rainfall duration is less than 3 h,ωf andμhave no significant effect on the safety factor,whereas it decreases with increasingωf and increases with increasingμunder longer duration(≥3 h).With the increase ofω_(f),the slope maximum instability time advances by 10.5 h,and with the increase ofμ,the slope maximum instability time delays by 3.1 h.展开更多
The Upper Chao Phraya River Basin, Thailand, has been facing continuous groundwater level decreases due to over-extraction for irrigation. MAR （managed aquifer recharge） using infiltration pond was investigated and ...The Upper Chao Phraya River Basin, Thailand, has been facing continuous groundwater level decreases due to over-extraction for irrigation. MAR （managed aquifer recharge） using infiltration pond was investigated and constructed. A recharge experiment at the pilot site at Ban Nong Na, Phitsanulok Province, was conducted during 2009 to 2011 to mitigate the declining shallow groundwater level. The HELP3 and MODFLOW models were applied to explore the current groundwater recharge. The MODFLOW was used to simulate the recharge mechanism of the experiment in the 1,260 m2 infiltration pond during July to November, 2010. The simulated results showed the groundwater influx and outflux for the year 2010 were 1.34 Mm3 1.57 Mm3, respectively. The annual shallow groundwater extraction was 1.40 Mm3 resulting in the groundwater system deficit of 0.23 Mm3 and causing groundwater level decline at the rate of 0.25 m/yr. The critical zone with groundwater level deeper than 8 m from the ground surface covers 19% of the study area of 4.12 km2 and it would be increased up to 85% within the next 10 years （2020）. To achieve the groundwater system balance, the deficit amount of 0.23 Mm3 is needed and six infiltration ponds are required.展开更多
基金funded by the National Basic Research Program of China (2013CB429902)the National Natural Science Foundation of China (U1303181, 41671032)
文摘A knowledge of soil permeability is essential to evaluate hydrologic characteristics of soil, such as water storage and water movement, and soil permeability coefficient is an important parameter that reflects soil permeability. In order to confirm the acceptability of the one-dimensional horizontal infiltration method（one-D method） for simultaneously determining both the saturated and unsaturated permeability coefficients of loamy sand, we first measured the cumulative infiltration and the wetting front distance under various infiltration heads through a series of one-dimensional horizontal infiltration experiments, and then analyzed the relationships of the cumulative horizontal infiltration with the wetting front distance and the square root of infiltration time. We finally compared the permeability results from Gardner model based on the one-D method with the results from other two commonly-used methods（i.e., constant head method and van Genuchten model） to evaluate the acceptability and applicability of the one-D method. The results showed that there was a robust linear relationship between the cumulative horizontal infiltration and the wetting front distance, suggesting that it is more appropriate to take the soil moisture content after infiltration in the entire wetted zone as the average soil moisture content than as the saturated soil moisture content. The results also showed that there was a robust linear relationship between the cumulative horizontal infiltration and the square root of infiltration time, suggesting that the Philip infiltration formula can better reflect the characteristics of cumulative horizontal infiltration under different infiltration heads. The following two facts indicate that it is feasible to use the one-D method for simultaneously determining the saturated and unsaturated permeability coefficients of loamy sand. First, the saturated permeability coefficient（prescribed in the Gardner model） of loamy sand obtained from the one-D method well agreed with the value obtained from the constant head method. Second, the relationship of unsaturated permeability coefficient with soil water suction for loamy sand calculated using Gardner model based on the one-D method was nearly identical with the same relationship calculated using van Genuchten model.
基金funded by the Natural Science Foundation of Fujian Province(Grant No.2023J011133)。
文摘Infiltration–runoff–slope instability mechanism of macropore slope under heavy rainfall is unclear.This paper studied its instability mechanism with an improved Green–Ampt(GA)model considering the dual-porosity(i.e.,matrix and macropore)and ponding condition,and proposed the infiltration equations,infiltration–runoff coupled model,and safety factor calculation method.Results show that the infiltration processes of macropore slope can be divided into three stages,and the proposed model is rational by a comparative analysis.The wetting front depth of the traditional unsaturated slope is 17.2%larger than that of the macropore slope in the early rainfall stage and 27%smaller than that of the macropore slope in the late rainfall stage.Then,macropores benefit the slope stability in the early rainfall but not in the latter.Macropore flow does not occur initially but becomes pronounced with increasing rainfall duration.The equal depth of the wetting front in the two domains is regarded as the onset criteria of macropore flow.Parameter analysis shows that macropore flow is delayed by increasing proportion of macropore domain(ω_(f)),whereas promoted by increasing ratio of saturated permeability coefficients between the two domains(μ).The increasing trend of ponding depth is sharp at first and then grows slowly.Finally,when rainfall duration is less than 3 h,ωf andμhave no significant effect on the safety factor,whereas it decreases with increasingωf and increases with increasingμunder longer duration(≥3 h).With the increase ofω_(f),the slope maximum instability time advances by 10.5 h,and with the increase ofμ,the slope maximum instability time delays by 3.1 h.
文摘The Upper Chao Phraya River Basin, Thailand, has been facing continuous groundwater level decreases due to over-extraction for irrigation. MAR （managed aquifer recharge） using infiltration pond was investigated and constructed. A recharge experiment at the pilot site at Ban Nong Na, Phitsanulok Province, was conducted during 2009 to 2011 to mitigate the declining shallow groundwater level. The HELP3 and MODFLOW models were applied to explore the current groundwater recharge. The MODFLOW was used to simulate the recharge mechanism of the experiment in the 1,260 m2 infiltration pond during July to November, 2010. The simulated results showed the groundwater influx and outflux for the year 2010 were 1.34 Mm3 1.57 Mm3, respectively. The annual shallow groundwater extraction was 1.40 Mm3 resulting in the groundwater system deficit of 0.23 Mm3 and causing groundwater level decline at the rate of 0.25 m/yr. The critical zone with groundwater level deeper than 8 m from the ground surface covers 19% of the study area of 4.12 km2 and it would be increased up to 85% within the next 10 years （2020）. To achieve the groundwater system balance, the deficit amount of 0.23 Mm3 is needed and six infiltration ponds are required.
