The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Stefania Tamea - One of the best experts on this subject based on the ideXlab platform.
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Stochastic Water Table dynamics in groundWater-dependent ecosystems
2020Co-Authors: Ignacio Rodriguez-iturbe, Stefania Tamea, Paolo D'odorico, Francesco Laio, Luca RidolfiAbstract:Humidlands are environments where the groundWater plays a key role on the ecosystem function. Contrary to Water limited ecosystems, where Water Table is mostly out of reach for the vegetation, groundWater-dependent ecosystems exhibit important interactions between the Water Table and vegetation dynamics. We propose here an analytical model to study the interactions between rainfall, Water Table and vegetation in humidland ecosystems. The groundWater dynamics is studied as a random process, stochastically driven by a marked Poisson noise representing rainfall events. Infiltration, root Water uptake, Water flow to/from an external Water body, and capillary rise are accounted for in a probabilistic description of Water Table fluctuations. We obtain analytical expressions for the steady-state probability distribution of Water Table depth, which allows us to investigate the long term behavior of Water Table dynamics, and their sensitivity to changes in climate, vegetation cover, and Water management
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ecohydrology of groundWater dependent ecosystems 1 stochastic Water Table dynamics
Water Resources Research, 2009Co-Authors: Francesco Laio, Stefania Tamea, Luca Ridolfi, Paolo Dodorico, Ignacio RodrigueziturbeAbstract:[1] Areas with a relatively shallow Water Table are environments where the groundWater plays a key role on the ecosystem function, and important interactions exist between hydrology and ecosystem processes. We propose here an analytical model to study the interactions between rainfall, Water Table, and vegetation in groundWater-dependent ecosystems. The Water Table dynamics are studied as a random process stochastically driven by a marked Poisson noise representing rainfall events. Infiltration, root Water uptake, Water flow to/from an external Water body, and capillary rise are accounted for in a probabilistic description of Water Table fluctuations. We obtain analytical expressions for the steady state probability distribution of Water Table depth, which allows us to investigate the long-term behavior of Water Table dynamics, and their sensitivity to changes in climate, vegetation cover, and Water management.
Ignacio Rodrigueziturbe - One of the best experts on this subject based on the ideXlab platform.
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ecohydrology of groundWater dependent ecosystems 1 stochastic Water Table dynamics
Water Resources Research, 2009Co-Authors: Francesco Laio, Stefania Tamea, Luca Ridolfi, Paolo Dodorico, Ignacio RodrigueziturbeAbstract:[1] Areas with a relatively shallow Water Table are environments where the groundWater plays a key role on the ecosystem function, and important interactions exist between hydrology and ecosystem processes. We propose here an analytical model to study the interactions between rainfall, Water Table, and vegetation in groundWater-dependent ecosystems. The Water Table dynamics are studied as a random process stochastically driven by a marked Poisson noise representing rainfall events. Infiltration, root Water uptake, Water flow to/from an external Water body, and capillary rise are accounted for in a probabilistic description of Water Table fluctuations. We obtain analytical expressions for the steady state probability distribution of Water Table depth, which allows us to investigate the long-term behavior of Water Table dynamics, and their sensitivity to changes in climate, vegetation cover, and Water management.
Peter Nielsen - One of the best experts on this subject based on the ideXlab platform.
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Behavior of a shallow Water Table under periodic flow conditions
Water Resources Research, 2009Co-Authors: Nick Cartwright, Peter Nielsen, Pierre PerrochetAbstract:A new laboratory data set on the behavior of a shallow Water Table in a sand column aquifer subject to simple harmonic periodic forcing at its base is presented and discussed. The data are analyzed using the dynamic effective porosity, which is defined as the ratio of the rate of change in total moisture to the rate of change in Water Table elevation; thus, a reduction in this parameter means that the extent of moisture exchange has been reduced relative to a given Water Table fluctuation. The data show a clear decrease in the dynamic effective porosity with increasing proximity of the Water Table to the sand surface, which is consistent with previous research under a steadily rising or falling shallow Water Table. The observed reduction in moisture exchange due to shallowness of the Water Table has implications for periodic flow scenarios such as the propagation of Water Table waves in coastal and beach groundWater systems. That is, as moisture exchange is reduced, less work is being done by the flow, and thus, energy dissipation rates for shallow Water Tables will be reduced relative to the case of a deeper Water Table. At present no account of the influence of Water Table shallowness has been included in theories describing Water Table wave dispersion. The present experiments, in conjunction with the dynamic effective porosity concept, provide a framework in which this gap in knowledge can be further investigated. Additional experiments were designed such that the free surface transgressed the sand surface for part of the oscillation period to investigate the influence of meniscus formation and deformation at the sand surface on periodic flow dynamics. The observed behavior is consistent with previous observations of steady infiltration above shallow Water Tables, namely, a rapid drop (rise) in pore pressure with the onset of meniscus formation (deformation). A simple "wetting and drying'' model is derived, accounting for the variation in effective porosity caused by the free surface transgressing the sand surface, which is shown to accurately capture the observed behavior. A finite element solution of the Richards equation in which the transient upper boundary condition is easily mimicked by means of a surface element with special storage features also shows excellent agreement with the observed data.
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tidal dynamics of the Water Table in beaches
Water Resources Research, 1990Co-Authors: Peter NielsenAbstract:Tidal motions of the Water Table height inside a sloping beach are investigated via field measurements and theoretical considerations. Only the movements forced by the tide are considered, so a beach with negligible wave activity was chosen for the field measurements. The data show that even in the absence of precipitation the time averaged inland Water Table stands considerably above the mean sea level. Also the Water Table at a fixed point inside the beach is far from sinusoidal even though its variation is forced by an essentially sinusoidal tide. This latter effect is due to the boundary condition along the sloping beach face which acts as a highly nonlinear filter. The observed behavior of the Water Table is explained in terms of perturbation extensions to the classical “deep aquifer solution.” One extension deals with the nonlinearity in the interior, the other with the boundary condition at the sloping beach face.
Francesco Laio - One of the best experts on this subject based on the ideXlab platform.
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Stochastic Water Table dynamics in groundWater-dependent ecosystems
2020Co-Authors: Ignacio Rodriguez-iturbe, Stefania Tamea, Paolo D'odorico, Francesco Laio, Luca RidolfiAbstract:Humidlands are environments where the groundWater plays a key role on the ecosystem function. Contrary to Water limited ecosystems, where Water Table is mostly out of reach for the vegetation, groundWater-dependent ecosystems exhibit important interactions between the Water Table and vegetation dynamics. We propose here an analytical model to study the interactions between rainfall, Water Table and vegetation in humidland ecosystems. The groundWater dynamics is studied as a random process, stochastically driven by a marked Poisson noise representing rainfall events. Infiltration, root Water uptake, Water flow to/from an external Water body, and capillary rise are accounted for in a probabilistic description of Water Table fluctuations. We obtain analytical expressions for the steady-state probability distribution of Water Table depth, which allows us to investigate the long term behavior of Water Table dynamics, and their sensitivity to changes in climate, vegetation cover, and Water management
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ecohydrology of groundWater dependent ecosystems 1 stochastic Water Table dynamics
Water Resources Research, 2009Co-Authors: Francesco Laio, Stefania Tamea, Luca Ridolfi, Paolo Dodorico, Ignacio RodrigueziturbeAbstract:[1] Areas with a relatively shallow Water Table are environments where the groundWater plays a key role on the ecosystem function, and important interactions exist between hydrology and ecosystem processes. We propose here an analytical model to study the interactions between rainfall, Water Table, and vegetation in groundWater-dependent ecosystems. The Water Table dynamics are studied as a random process stochastically driven by a marked Poisson noise representing rainfall events. Infiltration, root Water uptake, Water flow to/from an external Water body, and capillary rise are accounted for in a probabilistic description of Water Table fluctuations. We obtain analytical expressions for the steady state probability distribution of Water Table depth, which allows us to investigate the long-term behavior of Water Table dynamics, and their sensitivity to changes in climate, vegetation cover, and Water management.
Mahmood Nachabe - One of the best experts on this subject based on the ideXlab platform.
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evapotranspiration of two vegetation covers in a shallow Water Table environment
Soil Science Society of America Journal, 2005Co-Authors: Mahmood Nachabe, Nirjhar Shah, Mark Ross, Jeff VomackaAbstract:A method is introduced to estimate evapotranspiration (ET) in shallow Water Table environments. The method involves measuring the diurnal fluctuations in total soil moisture above the Water Table to estimate (i) the net lateral and vertical subsurface flux in the aquifer and (ii) evapotranspiration from the vegetation cover. In a hillslope discharge zone, the net lateral subsurface flux was calculated from the recovery rate of soil moisture between midnight and 0400 h. Evapotranspiration was then estimated from a daily Water balance in a soil column that included the Water Table. The method was tested on two vegetation covers, a pasture in a groundWater recharge area, and a riparian zone with woody vegetation in a groundWater discharge area. A moisture probe carrying eight sensors was used in each area to estimate the total soil moisture in a sandy soil environment. The observed Water Table fluctuated between land surface and a depth of 1.2 m during the study period, allowing observation and estimation of the total soil moisture in a soil column that included the Water Table. The results of this investigation support another hypothesis that, in humid, shallow Water Table environments, ET demand may be supported by adjacent ecosystems. This method provided reasonable results for the two landscapes investigated and was able to capture the variability of evapotranspiration in heterogeneous vegetation covers. It provided a relatively inexpensive alternative to characterize ET within regionally heterogeneous but microhomogenous landscapes. Though tested for coarse-textured soil, the method involving soil moisture monitoring can be easily adapted to other soil types with shallow Water Table. Another advantage of using this method is that ET can be successfully estimated without detailed knowledge of soil hydraulic properties, subsurface flow patterns, or vegetation characteristics.
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analytical expressions for transient specific yield and shallow Water Table drainage
Water Resources Research, 2002Co-Authors: Mahmood NachabeAbstract:[1] New closed-form expressions are introduced to capture the dependence of specific yield on time and depth to Water Table. The expressions allow the user to convert observations of Water Table fluctuations to volumes of Water released from storage in a shallow Water Table aquifer. Whereas a linear relationship between Water Table fluctuations and released volumes holds for a deep Water Table aquifer, this relationship is nonlinear for shallow Water Table aquifers. The dependence of specific yield on time stems from the slow drainage of soil Water from pores above the Water Table. The new expressions allow determination of transient specific yield and time to drain the soil Water profile for a given Water Table fluctuation. If the time step in a numerical groundWater model is longer than the time for limiting specific yield, then a constant (time independent) specific yield can be justifiably adopted. The new expressions are easy to use and require knowledge of soil hydraulic properties which are readily available from soil Water retention data and surveys.
