Paolo Nasta | Università degli Studi di Napoli "Federico II" (original) (raw)

Papers by Paolo Nasta

This study explores the feasibility of identifying the effective soil hydraulic parameterization ... more This study explores the feasibility of identifying the effective soil hydraulic parameterization of a layered soil profile by using a conventional unsteady drainage experiment leading to field capacity. The flux-based field capacity criterion is attained by subjecting the soil profile to a synthetic drainage process implemented numerically in the Soil-Water-Atmosphere-Plant (SWAP) model. The effective hydraulic param-eterization is associated to either aggregated or equivalent parameters, the former being determined by the geometrical scaling theory while the latter is obtained through the inverse modeling approach. Outcomes from both these methods depend on information that is sometimes difficult to retrieve at local scale and rather challenging or virtually impossible at larger scales. The only knowledge of topsoil hydraulic properties, for example, as retrieved by a near-surface field campaign or a data assimilation technique, is often exploited as a proxy to determine effective soil hydraulic parameterization at the largest spatial scales. Comparisons of the effective soil hydraulic characterization provided by these three methods are conducted by discussing the implications for their use and accounting for the trade-offs between required input information and model output reliability. To better highlight the epistemic errors associated to the different effective soil hydraulic properties and to provide some more practical guidance, the layered soil profiles are then grouped by using the FAO textural classes. For the moderately heterogeneous soil profiles available, all three approaches guarantee a general good predictability of the actual field capacity values and provide adequate identification of the effective hydraulic parameters. Conversely, worse performances are encountered for the highly variable vertical heterogeneity, especially when resorting to the ''topsoil-only'' information. In general, the best performances are guaranteed by the equivalent parameters, which might be considered a reference for comparisons with other techniques. As might be expected, the information content of the soil hydraulic properties pertaining only to the uppermost soil horizon is rather inefficient and also not capable to map out the hydrologic behavior of the real vertical soil heterogeneity since the drainage process is significantly affected by profile layering in almost all cases.

Hillslopes represent basic landscape elements of the catchment hydrological global response. Unde... more Hillslopes represent basic landscape elements of the catchment hydrological global response. Understanding hillslope subsurface and overland flow response to rainfall events is of primary interest when managing land and water resources at catchment scale, as they represent key processes controlling water, sediments and pollutants transport. Experimental data concerning the hydrological conditions leading to the initiation of hillslope lateral subsurface response are quite rare, particularly in Mediterranean catchments, ...

Water Resources Research, 2013

1] Simultaneous scaling of soil water retention and hydraulic conductivity functions provides an ... more 1] Simultaneous scaling of soil water retention and hydraulic conductivity functions provides an effective means to characterize the heterogeneity and spatial variability of soil hydraulic properties in a given study area. The statistical significance of this approach largely depends on the number of soil samples collected. Unfortunately, direct measurement of the soil hydraulic functions is tedious, expensive and time consuming. Here we present a simple and cost-effective hybrid scaling approach that combines the use of ancillary information (e.g., particle-size distribution and soil bulk density) with direct measurements of saturated soil water content and saturated hydraulic conductivity. Our results demonstrate that the presented approach requires far fewer laboratory measurements than conventional scaling methods to adequately capture the spatial variability of soil hydraulic properties.

Appropriate parameterization of the soil hydraulic properties represents a key issue for reliable... more Appropriate parameterization of the soil hydraulic properties represents a key issue for reliable modeling water transport processes in soil. Many analytical relationships can be found in the literature to describe the soil hydraulic properties, namely the soil water retention and unsaturated hydraulic conductivity function, but the various facets of soil hydraulic behavior can hardly be kept in its wholeness by even complex parametric expressions. In case of structured and well-aggregated soils, we have developed soil hydraulic relations whose parameters maintain a physical meaning while improving the predictions of unsaturated conductivities. We assume that the soil water retention function is made up by a superposition of two distinct modalities, each of which is described by a Kosugi-type log-normal function. These two modalities can be schematically associated to a more textural and a more structural retention behavior, respectively. It is shown that these two components of the water retention response are linked by a weighting factor to which a physical meaning can also be given. An important and practical advantage of the proposed bimodal water retention function (bWRF) is that a closed-form analytical expression is obtained for the bimodal hydraulic conductivity function (bHCF). A sensitivity analysis and comparisons with experimental data are used to evaluate the proposed bimodal log-normal hydraulic functions and demonstrate their effectiveness of better predicting the hydraulic conductivity characteristic of soils.

We propose to improve the estimation of soil hydraulic properties by first using a bimodal analyt... more We propose to improve the estimation of soil hydraulic properties by first using a bimodal analytical relationship to describe the water retention function. Basically a superposition of structural and textural unimodal components represents the behavior of bimodal pore-size distribution. Each of these water retention functions is described by a Kosugi-type log-normal function, with parameters being associated to the soil pore-size distribution. The two components of the water retention response are linked by a ...

Journal of Hydrology, 2009

The application of spatially distributed hydrological models is a challenging problem, particular... more The application of spatially distributed hydrological models is a challenging problem, particularly because of the difficulties arising in the identification of the model parameters describing the soil hydraulic properties and their spatial variability. Generally soil data are available just for a limited number of locations across the study area and very often the available data consist of soil physical and chemical properties rather than direct measurements of the soil hydraulic properties. Thus indirect methods are often required for an assessment of model parameters describing the soil hydraulic properties, based on a limited number of measurements.

Soil Science Society of America Journal, Mar 1, 2011

Geophysical Research Abstracts, 2007

The accurate description of the spatial and temporal variability of soil water content is a key i... more The accurate description of the spatial and temporal variability of soil water content is a key issue for hydrological applications. In this study we investigated the spatial variability of the soil water content at the hillslope scale within a sub-humid area in Southern Italy. Six hillslope transects have been selected across the main soil-landscape units of a 40 km2 catchment. The selected transects have slope gradients ranging from 10% up to 50%. Landuse is dominated by pasture, Mediterranean macchia and orchard. Surface soil ...

Water Resources Research, 2013

1] Prediction of flow through variably saturated porous media requires accurate knowledge of the ... more 1] Prediction of flow through variably saturated porous media requires accurate knowledge of the soil hydraulic properties, namely the water retention function (WRF) and the hydraulic conductivity function (HCF). Unfortunately, direct measurement of the HCF is time consuming and expensive. In this study, we derive a simple closed-form equation that predicts the saturated hydraulic conductivity, K s from the WRF parameters of . This physically based analytical expression uses an empirical tortuosity parameter () and exploits the information embedded in the measured pore-size distribution. Our proposed model is compared against the current state of the art using more than 250 soil samples from the Grenoble soil catalog (GRIZZLY) and hydraulic properties of European soils (HYPRES) databases. Results demonstrate that the proposed model provides better predictions of the saturated hydraulic conductivity values with reduced size of the 90% confidence intervals of about 3 orders of magnitude.

To overcome some drawbacks of the unimodal relations commonly used to describe soil hydraulic pro... more To overcome some drawbacks of the unimodal relations commonly used to describe soil hydraulic properties (SHPs), previously we developed bimodal lognormal relations that have the following main features: (i) they are closed-form expressions, (ii) they have a sound theoretical basis and provide a more general conceptualization of soil and (iii) they improve the description of both the water retention (WRF) and hydraulic conductivity (HCF) functions. Nevertheless, the reliability of soil hydraulic analytical relations is often tested only at the curve fitting level. Comparisons between unimodal and bimodal soil hydraulic relations are more effective and informative when performed within a functional evaluation approach. We use the HYDRUS-1D package to quantify and compare soil moisture dynamics and storage regimes for hydrological processes at both the event and annual timescales when the soil domain is characterized by either unimodal or bimodal hydraulic properties. Seven soil samples taken from a previous study were used in numerical simulations of drainage or infiltration processes; there were large relative discrepancies in terms of simulated soil water storage. A subsequent test that involved simulations of soil water budget for the period 2000–2012 was implemented for a peach-orchard field by a conventional scaling method. This test also enables soil spatial variation to be taken into consideration. Two different scenarios enable the epistemic uncertainty to be evaluated when different hydraulic models are considered for soil with weak or strong bimodality. With Willmott's refined index of agreement, discrepancies in soil water storage were about 15% (weak bimodality) or more than 30% (strong bimodality). Highlights • Main aim of this study is the assessment of epistemic uncertainty in modelling soil water dynamics. • We make functional evaluations for both event-based and long-term hydrological processes. • Disregard of bimodal soil hydraulic behaviour can lead to large epistemic errors. • Better predictions of soil hydraulic properties should be sought in future research.

Procedia Environmental Sciences, 2013

Management interaction am the spatial an models. In th humid area in recorded by a dam in the o g... more Management interaction am the spatial an models. In th humid area in recorded by a dam in the o grassland and delineated alo portable TDR October 2004 wet winters w instability and near saturatio runoff and su and the wetne

Water Resources Research, 2014

1] Variability in sediment hydraulic properties associated with landscape depositional and erosio... more 1] Variability in sediment hydraulic properties associated with landscape depositional and erosional features can influence groundwater recharge processes by affecting soil-water storage and transmission. This study considers recharge to aquifers underlying river-incised glaciated terrain where the distribution of clay-rich till is largely intact in upland locations but has been removed by alluvial erosion in stream valleys. In a stream-dissected glacial region in eastern Nebraska (Great Plains region of the United States), recharge estimates were developed for nested profile, aquifer, and regional scales using unsaturated zone profile measurements (matric potentials, Cl 2 and 3 H), groundwater tracers (CFC-12 and SF 6 ), and a remote sensing-assisted water balance model. Results show a consistent influence of till lithology on recharge rates across nested spatial scales despite substantial uncertainty in all recharge estimation methods, suggesting that minimal diffuse recharge occurs through upland glacial till lithology whereas diffuse recharge occurs in river valleys where till is locally absent. Diffuse recharge is estimated to account for a maximum of 61% of total recharge based on comparison of diffuse recharge estimated from the unsaturated zone (0-43 mm yr 21 ) and total recharge estimated from groundwater tracers (median 58 mm yr 21 ) and water balance modeling (median 56 mm yr 21 ). The results underscore the importance of lithologic controls on the distributions of both recharge rates and mechanisms.

Procedia Environmental Sciences, 2013

Reliable large-scale characterization of soil water retention (WRF) and hydraulic conductivity (H... more Reliable large-scale characterization of soil water retention (WRF) and hydraulic conductivity (HCF) functions requires a large amount of direct measurements for hydrological modeling applications. Although direct measurements of WRF are time consuming, they tend to be far less time and labor-intensive than direct measurements of HCF. Therefore, WRF experimental data are often exploited to predict the HCF through available existing models. Current popular approaches include the well known physically-based Mualem's model. We hereby propose a novel, simple and physically sound model to predict the relative HCF from Kosugi's WRF expression . The proposed model is based on the introduction of a new conductivity parameter, , that is related to the coefficient of variation of the WRF. The model is calibrated on 20 soil samples and subsequently tested on an independent data set of 57 samples. The predictions show relatively high accuracy and reliability when compared to those derived from Mualem's model.

Soil Science, 2013

Effective soil hydraulic parameters of soil vegetation atmosphere transfer (SVAT) models can be d... more Effective soil hydraulic parameters of soil vegetation atmosphere transfer (SVAT) models can be derived in a cost-efficient way by inverse modeling. Nevertheless, a serious drawback of SVAT models based on Richards' equation is that they require as many as five unexploited correlated hydraulic parameters. To reduce the feasible parameter space, we propose a method to prevent nonphysical combinations of soil hydraulic parameter sets obtained by optimization. We adopt the soil hydraulic analytical model by Kosugi because it enables the feasible parameter space to be reduced by predicting parameter σ from R m , which are the variance and mean of the log-transformed soil pore radius, respectively. To further decrease the parameter space, we derive two models to predict saturated hydraulic conductivity, K s , from three or four Kosugi soil water retention parameters, respectively. These two models are based on the combination of the Hagen-Poiseuille and Darcy equations that use three semiempirical parameters (τ 1 , τ 2 , and τ 3 ) calibrated on large UNSODA and HYPRES databases. Our derived models are compared with a version of the Mishra and Parker (1990. Ground Water. 28:775-777) K s model being modified to account for the parameters of Kosugi's relationships. The results show that the uncertainties of the developed K s model are comparable to the uncertainties of K s measurements. Moreover, the developed K s model outperforms the Mishra and Parker model. Therefore, the developed method will enable one to substantially reduce the feasible range of the inverted Kosugi's hydraulic parameters.

Soil Science Society of America Journal, 2011

Journal of Hydrology, 2009

The application of spatially distributed hydrological models is a challenging problem, particular... more The application of spatially distributed hydrological models is a challenging problem, particularly because of the difficulties arising in the identification of the model parameters describing the soil hydraulic properties and their spatial variability. Generally soil data are available just for a limited number of locations across the study area and very often the available data consist of soil physical and chemical properties rather than direct measurements of the soil hydraulic properties. Thus indirect methods are often required for an assessment of model parameters describing the soil hydraulic properties, based on a limited number of measurements.

Hydrological Sciences Journal, 2013

Agricultural Water Management, 2013

EGU General Assembly 2010, held 2-7 May, 2010 in Vienna, Austria, p. 3870, May 1, 2010

Appropriate parameterization of the soil hydraulic properties represents a key issue for reliable... more Appropriate parameterization of the soil hydraulic properties represents a key issue for reliable modeling water transport processes in soil. Many analytical relationships can be found in the literature to describe the soil hydraulic properties, namely the soil water retention and unsaturated hydraulic conductivity function, but the various facets of soil hydraulic behavior can hardly be kept in its wholeness by even complex parametric expressions. In case of structured and well-aggregated soils, we have developed soil ...

Water Resources Research, 2013

1] Prediction of flow through variably saturated porous media requires accurate knowledge of the ... more 1] Prediction of flow through variably saturated porous media requires accurate knowledge of the soil hydraulic properties, namely the water retention function (WRF) and the hydraulic conductivity function (HCF). Unfortunately, direct measurement of the HCF is time consuming and expensive. In this study, we derive a simple closed-form equation that predicts the saturated hydraulic conductivity, K s from the WRF parameters of . This physically based analytical expression uses an empirical tortuosity parameter () and exploits the information embedded in the measured pore-size distribution. Our proposed model is compared against the current state of the art using more than 250 soil samples from the Grenoble soil catalog (GRIZZLY) and hydraulic properties of European soils (HYPRES) databases. Results demonstrate that the proposed model provides better predictions of the saturated hydraulic conductivity values with reduced size of the 90% confidence intervals of about 3 orders of magnitude.

This study explores the feasibility of identifying the effective soil hydraulic parameterization ... more This study explores the feasibility of identifying the effective soil hydraulic parameterization of a layered soil profile by using a conventional unsteady drainage experiment leading to field capacity. The flux-based field capacity criterion is attained by subjecting the soil profile to a synthetic drainage process implemented numerically in the Soil-Water-Atmosphere-Plant (SWAP) model. The effective hydraulic param-eterization is associated to either aggregated or equivalent parameters, the former being determined by the geometrical scaling theory while the latter is obtained through the inverse modeling approach. Outcomes from both these methods depend on information that is sometimes difficult to retrieve at local scale and rather challenging or virtually impossible at larger scales. The only knowledge of topsoil hydraulic properties, for example, as retrieved by a near-surface field campaign or a data assimilation technique, is often exploited as a proxy to determine effective soil hydraulic parameterization at the largest spatial scales. Comparisons of the effective soil hydraulic characterization provided by these three methods are conducted by discussing the implications for their use and accounting for the trade-offs between required input information and model output reliability. To better highlight the epistemic errors associated to the different effective soil hydraulic properties and to provide some more practical guidance, the layered soil profiles are then grouped by using the FAO textural classes. For the moderately heterogeneous soil profiles available, all three approaches guarantee a general good predictability of the actual field capacity values and provide adequate identification of the effective hydraulic parameters. Conversely, worse performances are encountered for the highly variable vertical heterogeneity, especially when resorting to the ''topsoil-only'' information. In general, the best performances are guaranteed by the equivalent parameters, which might be considered a reference for comparisons with other techniques. As might be expected, the information content of the soil hydraulic properties pertaining only to the uppermost soil horizon is rather inefficient and also not capable to map out the hydrologic behavior of the real vertical soil heterogeneity since the drainage process is significantly affected by profile layering in almost all cases.

Hillslopes represent basic landscape elements of the catchment hydrological global response. Unde... more Hillslopes represent basic landscape elements of the catchment hydrological global response. Understanding hillslope subsurface and overland flow response to rainfall events is of primary interest when managing land and water resources at catchment scale, as they represent key processes controlling water, sediments and pollutants transport. Experimental data concerning the hydrological conditions leading to the initiation of hillslope lateral subsurface response are quite rare, particularly in Mediterranean catchments, ...

Water Resources Research, 2013

1] Simultaneous scaling of soil water retention and hydraulic conductivity functions provides an ... more 1] Simultaneous scaling of soil water retention and hydraulic conductivity functions provides an effective means to characterize the heterogeneity and spatial variability of soil hydraulic properties in a given study area. The statistical significance of this approach largely depends on the number of soil samples collected. Unfortunately, direct measurement of the soil hydraulic functions is tedious, expensive and time consuming. Here we present a simple and cost-effective hybrid scaling approach that combines the use of ancillary information (e.g., particle-size distribution and soil bulk density) with direct measurements of saturated soil water content and saturated hydraulic conductivity. Our results demonstrate that the presented approach requires far fewer laboratory measurements than conventional scaling methods to adequately capture the spatial variability of soil hydraulic properties.

Appropriate parameterization of the soil hydraulic properties represents a key issue for reliable... more Appropriate parameterization of the soil hydraulic properties represents a key issue for reliable modeling water transport processes in soil. Many analytical relationships can be found in the literature to describe the soil hydraulic properties, namely the soil water retention and unsaturated hydraulic conductivity function, but the various facets of soil hydraulic behavior can hardly be kept in its wholeness by even complex parametric expressions. In case of structured and well-aggregated soils, we have developed soil hydraulic relations whose parameters maintain a physical meaning while improving the predictions of unsaturated conductivities. We assume that the soil water retention function is made up by a superposition of two distinct modalities, each of which is described by a Kosugi-type log-normal function. These two modalities can be schematically associated to a more textural and a more structural retention behavior, respectively. It is shown that these two components of the water retention response are linked by a weighting factor to which a physical meaning can also be given. An important and practical advantage of the proposed bimodal water retention function (bWRF) is that a closed-form analytical expression is obtained for the bimodal hydraulic conductivity function (bHCF). A sensitivity analysis and comparisons with experimental data are used to evaluate the proposed bimodal log-normal hydraulic functions and demonstrate their effectiveness of better predicting the hydraulic conductivity characteristic of soils.

We propose to improve the estimation of soil hydraulic properties by first using a bimodal analyt... more We propose to improve the estimation of soil hydraulic properties by first using a bimodal analytical relationship to describe the water retention function. Basically a superposition of structural and textural unimodal components represents the behavior of bimodal pore-size distribution. Each of these water retention functions is described by a Kosugi-type log-normal function, with parameters being associated to the soil pore-size distribution. The two components of the water retention response are linked by a ...

Journal of Hydrology, 2009

The application of spatially distributed hydrological models is a challenging problem, particular... more The application of spatially distributed hydrological models is a challenging problem, particularly because of the difficulties arising in the identification of the model parameters describing the soil hydraulic properties and their spatial variability. Generally soil data are available just for a limited number of locations across the study area and very often the available data consist of soil physical and chemical properties rather than direct measurements of the soil hydraulic properties. Thus indirect methods are often required for an assessment of model parameters describing the soil hydraulic properties, based on a limited number of measurements.

Soil Science Society of America Journal, Mar 1, 2011

Geophysical Research Abstracts, 2007

The accurate description of the spatial and temporal variability of soil water content is a key i... more The accurate description of the spatial and temporal variability of soil water content is a key issue for hydrological applications. In this study we investigated the spatial variability of the soil water content at the hillslope scale within a sub-humid area in Southern Italy. Six hillslope transects have been selected across the main soil-landscape units of a 40 km2 catchment. The selected transects have slope gradients ranging from 10% up to 50%. Landuse is dominated by pasture, Mediterranean macchia and orchard. Surface soil ...

Water Resources Research, 2013

1] Prediction of flow through variably saturated porous media requires accurate knowledge of the ... more 1] Prediction of flow through variably saturated porous media requires accurate knowledge of the soil hydraulic properties, namely the water retention function (WRF) and the hydraulic conductivity function (HCF). Unfortunately, direct measurement of the HCF is time consuming and expensive. In this study, we derive a simple closed-form equation that predicts the saturated hydraulic conductivity, K s from the WRF parameters of . This physically based analytical expression uses an empirical tortuosity parameter () and exploits the information embedded in the measured pore-size distribution. Our proposed model is compared against the current state of the art using more than 250 soil samples from the Grenoble soil catalog (GRIZZLY) and hydraulic properties of European soils (HYPRES) databases. Results demonstrate that the proposed model provides better predictions of the saturated hydraulic conductivity values with reduced size of the 90% confidence intervals of about 3 orders of magnitude.

To overcome some drawbacks of the unimodal relations commonly used to describe soil hydraulic pro... more To overcome some drawbacks of the unimodal relations commonly used to describe soil hydraulic properties (SHPs), previously we developed bimodal lognormal relations that have the following main features: (i) they are closed-form expressions, (ii) they have a sound theoretical basis and provide a more general conceptualization of soil and (iii) they improve the description of both the water retention (WRF) and hydraulic conductivity (HCF) functions. Nevertheless, the reliability of soil hydraulic analytical relations is often tested only at the curve fitting level. Comparisons between unimodal and bimodal soil hydraulic relations are more effective and informative when performed within a functional evaluation approach. We use the HYDRUS-1D package to quantify and compare soil moisture dynamics and storage regimes for hydrological processes at both the event and annual timescales when the soil domain is characterized by either unimodal or bimodal hydraulic properties. Seven soil samples taken from a previous study were used in numerical simulations of drainage or infiltration processes; there were large relative discrepancies in terms of simulated soil water storage. A subsequent test that involved simulations of soil water budget for the period 2000–2012 was implemented for a peach-orchard field by a conventional scaling method. This test also enables soil spatial variation to be taken into consideration. Two different scenarios enable the epistemic uncertainty to be evaluated when different hydraulic models are considered for soil with weak or strong bimodality. With Willmott's refined index of agreement, discrepancies in soil water storage were about 15% (weak bimodality) or more than 30% (strong bimodality). Highlights • Main aim of this study is the assessment of epistemic uncertainty in modelling soil water dynamics. • We make functional evaluations for both event-based and long-term hydrological processes. • Disregard of bimodal soil hydraulic behaviour can lead to large epistemic errors. • Better predictions of soil hydraulic properties should be sought in future research.

Procedia Environmental Sciences, 2013

Management interaction am the spatial an models. In th humid area in recorded by a dam in the o g... more Management interaction am the spatial an models. In th humid area in recorded by a dam in the o grassland and delineated alo portable TDR October 2004 wet winters w instability and near saturatio runoff and su and the wetne

Water Resources Research, 2014

1] Variability in sediment hydraulic properties associated with landscape depositional and erosio... more 1] Variability in sediment hydraulic properties associated with landscape depositional and erosional features can influence groundwater recharge processes by affecting soil-water storage and transmission. This study considers recharge to aquifers underlying river-incised glaciated terrain where the distribution of clay-rich till is largely intact in upland locations but has been removed by alluvial erosion in stream valleys. In a stream-dissected glacial region in eastern Nebraska (Great Plains region of the United States), recharge estimates were developed for nested profile, aquifer, and regional scales using unsaturated zone profile measurements (matric potentials, Cl 2 and 3 H), groundwater tracers (CFC-12 and SF 6 ), and a remote sensing-assisted water balance model. Results show a consistent influence of till lithology on recharge rates across nested spatial scales despite substantial uncertainty in all recharge estimation methods, suggesting that minimal diffuse recharge occurs through upland glacial till lithology whereas diffuse recharge occurs in river valleys where till is locally absent. Diffuse recharge is estimated to account for a maximum of 61% of total recharge based on comparison of diffuse recharge estimated from the unsaturated zone (0-43 mm yr 21 ) and total recharge estimated from groundwater tracers (median 58 mm yr 21 ) and water balance modeling (median 56 mm yr 21 ). The results underscore the importance of lithologic controls on the distributions of both recharge rates and mechanisms.

Procedia Environmental Sciences, 2013

Reliable large-scale characterization of soil water retention (WRF) and hydraulic conductivity (H... more Reliable large-scale characterization of soil water retention (WRF) and hydraulic conductivity (HCF) functions requires a large amount of direct measurements for hydrological modeling applications. Although direct measurements of WRF are time consuming, they tend to be far less time and labor-intensive than direct measurements of HCF. Therefore, WRF experimental data are often exploited to predict the HCF through available existing models. Current popular approaches include the well known physically-based Mualem's model. We hereby propose a novel, simple and physically sound model to predict the relative HCF from Kosugi's WRF expression . The proposed model is based on the introduction of a new conductivity parameter, , that is related to the coefficient of variation of the WRF. The model is calibrated on 20 soil samples and subsequently tested on an independent data set of 57 samples. The predictions show relatively high accuracy and reliability when compared to those derived from Mualem's model.

Soil Science, 2013

Effective soil hydraulic parameters of soil vegetation atmosphere transfer (SVAT) models can be d... more Effective soil hydraulic parameters of soil vegetation atmosphere transfer (SVAT) models can be derived in a cost-efficient way by inverse modeling. Nevertheless, a serious drawback of SVAT models based on Richards' equation is that they require as many as five unexploited correlated hydraulic parameters. To reduce the feasible parameter space, we propose a method to prevent nonphysical combinations of soil hydraulic parameter sets obtained by optimization. We adopt the soil hydraulic analytical model by Kosugi because it enables the feasible parameter space to be reduced by predicting parameter σ from R m , which are the variance and mean of the log-transformed soil pore radius, respectively. To further decrease the parameter space, we derive two models to predict saturated hydraulic conductivity, K s , from three or four Kosugi soil water retention parameters, respectively. These two models are based on the combination of the Hagen-Poiseuille and Darcy equations that use three semiempirical parameters (τ 1 , τ 2 , and τ 3 ) calibrated on large UNSODA and HYPRES databases. Our derived models are compared with a version of the Mishra and Parker (1990. Ground Water. 28:775-777) K s model being modified to account for the parameters of Kosugi's relationships. The results show that the uncertainties of the developed K s model are comparable to the uncertainties of K s measurements. Moreover, the developed K s model outperforms the Mishra and Parker model. Therefore, the developed method will enable one to substantially reduce the feasible range of the inverted Kosugi's hydraulic parameters.

Soil Science Society of America Journal, 2011

Journal of Hydrology, 2009

The application of spatially distributed hydrological models is a challenging problem, particular... more The application of spatially distributed hydrological models is a challenging problem, particularly because of the difficulties arising in the identification of the model parameters describing the soil hydraulic properties and their spatial variability. Generally soil data are available just for a limited number of locations across the study area and very often the available data consist of soil physical and chemical properties rather than direct measurements of the soil hydraulic properties. Thus indirect methods are often required for an assessment of model parameters describing the soil hydraulic properties, based on a limited number of measurements.

Hydrological Sciences Journal, 2013

Agricultural Water Management, 2013

EGU General Assembly 2010, held 2-7 May, 2010 in Vienna, Austria, p. 3870, May 1, 2010

Appropriate parameterization of the soil hydraulic properties represents a key issue for reliable... more Appropriate parameterization of the soil hydraulic properties represents a key issue for reliable modeling water transport processes in soil. Many analytical relationships can be found in the literature to describe the soil hydraulic properties, namely the soil water retention and unsaturated hydraulic conductivity function, but the various facets of soil hydraulic behavior can hardly be kept in its wholeness by even complex parametric expressions. In case of structured and well-aggregated soils, we have developed soil ...

Water Resources Research, 2013

1] Prediction of flow through variably saturated porous media requires accurate knowledge of the ... more 1] Prediction of flow through variably saturated porous media requires accurate knowledge of the soil hydraulic properties, namely the water retention function (WRF) and the hydraulic conductivity function (HCF). Unfortunately, direct measurement of the HCF is time consuming and expensive. In this study, we derive a simple closed-form equation that predicts the saturated hydraulic conductivity, K s from the WRF parameters of . This physically based analytical expression uses an empirical tortuosity parameter () and exploits the information embedded in the measured pore-size distribution. Our proposed model is compared against the current state of the art using more than 250 soil samples from the Grenoble soil catalog (GRIZZLY) and hydraulic properties of European soils (HYPRES) databases. Results demonstrate that the proposed model provides better predictions of the saturated hydraulic conductivity values with reduced size of the 90% confidence intervals of about 3 orders of magnitude.

3. Results 4.Conclusions 1. Project context and motivations Assessing the impact of farmland aban... more 3. Results 4.Conclusions 1. Project context and motivations Assessing the impact of farmland abandonment on ecosystem services of a catchment in Southern Italy In mountainous areas of Mediterranean Europe farming systems have been subjected to progressive abandonment and subsequent expansion of forest during the second half of the 20th century. Therefore, an in-depth knowledge of the influence of afforestation on catchment-scale budget helps define proper trade-offs in regulating and provisioning Hydrologic Ecosystem Services (HES). While it is common evidence that afforestation increases the amount of water consumption and reduces downstream water availability at local or catchment scales (demand-side view), on the other hand, forest might be envisioned as a source of water that contributes in the intensification of the hydrologic cycle at regional or even continental scales (supply-side view). In a demand-side context, our major objective is to compute absolute and relative changes in the average annual and monthly water and sediment budgets by using available historical land-use/land-cover (LULC) maps built in 1955, 1998 and 2015. In contrast, in a supply-side point of view, a second target of this study encompasses the analysis of the relationship between monthly rainfall characteristics and simulated water yield.