Optimizing Pedotransfer Functions for Predicting Soil Moisture of Wetting Curve Based on the Effective Degree of Saturation

2021 ◽  
Vol 54 (3) ◽  
pp. 399-408
Author(s):  
A. Y. Mady ◽  
E. V. Shein
Keyword(s):  
Soil Moisture ◽  
Degree Of Saturation ◽  
Pedotransfer Functions ◽  
Wetting Curve ◽  
Effective Degree

A generally applicable pedotransfer function that estimates field capacity and permanent wilting point from soil texture and bulk density

2008 ◽  
Vol 88 (5) ◽  
pp. 761-774 ◽  
Author(s):  
J. A. P. Pollacco
Keyword(s):  
Organic Matter ◽  
Soil Moisture ◽  
Bulk Density ◽  
Soil Texture ◽  
The United States ◽  
Pedotransfer Functions ◽  
Pedotransfer Function ◽  
Data Set ◽  
Wide Range ◽  
Fitting Parameters

Hydrological models require the determination of fitting parameters that are tedious and time consuming to acquire. A rapid alternative method of estimating the fitting parameters is to use pedotransfer functions. This paper proposes a reliable method to estimate soil moisture at -33 and -1500 kPa from soil texture and bulk density. This method reduces the saturated moisture content by multiplying it with two non-linear functions depending on sand and clay contents. The novel pedotransfer function has no restrictions on the range of the texture predictors and gives reasonable predictions for soils with bulk density that varies from 0.25 to 2.16 g cm-3. These pedotransfer functions require only five parameters for each pressure head. It is generally accepted that the introduction of organic matter as a predictor improves the outcomes; however it was found by using a porosity based pedotransfer model, using organic matter as a predictor only modestly improves the accuracy. The model was developed employing 18 559 samples from the IGBP-DIS soil data set for pedotransfer function development (Data and Information System of the International Geosphere Biosphere Programme) database that embodies all major soils across the United States of America. The function is reliable and performs well for a wide range of soils occurring in very dry to very wet climates. Climatical grouping of the IGBP-DIS soils was proposed (aquic, tropical, cryic, aridic), but the results show that only tropical soils require specific grouping. Among many other different non-climatical soil groups tested, only humic and vitric soils were found to require specific grouping. The reliability of the pedotransfer function was further demonstrated with an independent database from Northern Italy having heterogeneous soils, and was found to be comparable or better than the accuracy of other pedotransfer functions found in the literature. Key words: Pedotransfer functions, soil moisture, soil texture, bulk density, organic matter, grouping

scholarly journals Estimating flow and transport parameters in the unsaturated zone with pore water stable isotopes

2015 ◽  
Vol 19 (6) ◽  
pp. 2617-2635 ◽  
Author(s):  
M. Sprenger ◽  
T. H. M. Volkmann ◽  
T. Blume ◽  
M. Weiler
Keyword(s):  
Soil Moisture ◽  
Stable Isotope ◽  
Solute Transport ◽  
Water Flow ◽  
Pore Water ◽  
Pedotransfer Functions ◽  
Transport Parameters ◽  
Soil Moisture Dynamics ◽  
Moisture Dynamics ◽  
Water Isotope

Abstract. Determining the soil hydraulic properties is a prerequisite to physically model transient water flow and solute transport in the vadose zone. Estimating these properties by inverse modelling techniques has become more common within the last 2 decades. While these inverse approaches usually fit simulations to hydrometric data, we expanded the methodology by using independent information about the stable isotope composition of the soil pore water depth profile as a single or additional optimization target. To demonstrate the potential and limits of this approach, we compared the results of three inverse modelling strategies where the fitting targets were (a) pore water isotope concentrations, (b) a combination of pore water isotope concentrations and soil moisture time series, and (c) a two-step approach using first soil moisture data to determine water flow parameters and then the pore water stable isotope concentrations to estimate the solute transport parameters. The analyses were conducted at three study sites with different soil properties and vegetation. The transient unsaturated water flow was simulated by solving the Richards equation numerically with the finite-element code of HYDRUS-1D. The transport of deuterium was simulated with the advection-dispersion equation, and a modified version of HYDRUS was used, allowing deuterium loss during evaporation. The Mualem–van Genuchten and the longitudinal dispersivity parameters were determined for two major soil horizons at each site. The results show that approach (a), using only the pore water isotope content, cannot substitute hydrometric information to derive parameter sets that reflect the observed soil moisture dynamics but gives comparable results when the parameter space is constrained by pedotransfer functions. Approaches (b) and (c), using both the isotope profiles and the soil moisture time series, resulted in good simulation results with regard to the Kling–Gupta efficiency and good parameter identifiability. However, approach (b) has the advantage that it considers the isotope data not only for the solute transport parameters but also for water flow and root water uptake, and thus increases parameter realism. Approaches (b) and (c) both outcompeted simulations run with parameters derived from pedotransfer functions, which did not result in an acceptable representation of the soil moisture dynamics and pore water stable isotope composition. Overall, parameters based on this new approach that includes isotope data lead to similar model performances regarding the water balance and soil moisture dynamics and better parameter identifiability than the conventional inverse model approaches limited to hydrometric fitting targets. If only data from isotope profiles in combination with textural information is available, the results are still satisfactory. This method has the additional advantage that it will not only allow us to estimate water balance and response times but also site-specific time variant transit times or solute breakthrough within the soil profile.

scholarly journals Using data assimilation to optimize pedotransfer functions using large-scale in-situ soil moisture observations

2020 ◽  
Author(s):  
Elizabeth Cooper ◽  
Eleanor Blyth ◽  
Hollie Cooper ◽  
Rich Ellis ◽  
Ewan Pinnington ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Data Assimilation ◽  
Land Surface ◽  
Large Scale ◽  
Pedotransfer Functions ◽  
Surface Model ◽  
Climate Projections ◽  
Land Surface Models ◽  
Surface Models

Abstract. Soil moisture predictions from land surface models are important in hydrological, ecological and meteorological applications. In recent years the availability of wide-area soil-moisture measurements has increased, but few studies have combined model-based soil moisture predictions with in-situ observations beyond the point scale. Here we show that we can markedly improve soil moisture estimates from the JULES land surface model using field scale observations and data assimilation techniques. Rather than directly updating soil moisture estimates towards observed values, we optimize constants in the underlying pedotransfer functions, which relate soil texture to JULES soil physics parameters. In this way we generate a single set of newly calibrated pedotransfer functions based on observations from a number of UK sites with different soil textures. We demonstrate that calibrating a pedotransfer function in this way can improve the performance of land surface models, leading to the potential for better flood, drought and climate projections.

scholarly journals Hydropedological parameters limiting soil moisture regime floodplain ecosystems of south Moravia

2005 ◽  
Vol 53 (1) ◽  
pp. 71-84
Author(s):  
Ladislav Kubík
Keyword(s):  
Soil Moisture ◽  
Water Retention ◽  
Humus Content ◽  
Field Capacity ◽  
Pedotransfer Functions ◽  
Physical Parameters ◽  
Moisture Regime ◽  
Floodplain Ecosystems ◽  
Soil Moisture Regime ◽  
Wilting Point

Soil moisture regime of floodplain ecosystems in southern Moravia is considerably influenced and greatly changed by human activities. It can be changed negatively by water management engineering or positively by landscape revitalizations. The paper deals with problems of hydropedological characteristics (hydrolimits) limiting soil moisture regime and solves effect of hydrological factors on soil moisture regime in the floodplain ecosystems. Attention is paid especially to water retention curves and to hydrolimits – wilting point and field capacity. They can be acquired either directly by slow laboratory assessment, derivation from the water retention curves or indirectly by calculation using pedotransfer functions (PTF). This indirect assessment uses hydrolimit dependency on better available soil physical parameters namely soil granularity, bulk density and humus content. The aim is to calculate PTF for wilting point and field capacity and to compare them with measured values. The paper documents suitableness utilization of PTF for the region of interest. The results of correlation and regression analysis for soil moisture and groundwater table are furthermore presented.

scholarly journals Effect of soil moisture content on the bearing capacity of small bored piles in the unsaturated soil of Maringá, Paraná, Brazil

2021 ◽  
Vol 337 ◽  
pp. 03006
Author(s):  
Verônica Ricken Marques ◽  
Antonio Belincanta ◽  
Mary-Antonette Beroya-Eitner ◽  
Jorge Luis Almada Augusto ◽  
Ewerton Guelssi ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Bearing Capacity ◽  
Water Content ◽  
Unsaturated Soil ◽  
Soil Layer ◽  
Matric Suction ◽  
Load Test ◽  
Degree Of Saturation ◽  
Static Load Test

In this study, the influence of soil moisture on the bearing capacity of piles founded in an unsaturated clay soil was investigated. The soil studied, composing the upper soil layer in Maringá, Brazil, is lateritic, has degree of saturation between 37% and 70% and has collapsible behaviour when wet. The bearing capacity was determined by full-scale load tests following the Brazilian Standard for Static Load Test. Two pile lengths, 4 m and 8 m, were considered. To analyse the influence of soil moisture, two tests were performed for each pile length: one in soil in its natural moisture content and another in pre-moistened soil. Results show that for both pile lengths, an increase in water content caused a significant reduction in bearing capacity, which is attributed to the decrease in the matric suction of the soil. This is confirmed by the results of the initial evaluation made on the variation of matric suction and its contribution to the bearing capacity with changes in water content. In summary, this study confirms that the pile bearing capacity in unsaturated soil is dependent on soil water content, highlighting the fact that the approach of assuming full saturation condition in the evaluation of the pile bearing capacity in such soil may give erroneous results. Moreover, this study demonstrate that the empirical methods most commonly used in Brazil for pile bearing capacity determination, the Décourt & Quaresma and Aoki & Velloso methods, are overly conservative when applied to the Maringá soil.

scholarly journals Developing an improved soil moisture dataset by blending passive and active microwave satellite-based retrievals

2011 ◽  
Vol 15 (2) ◽  
pp. 425-436 ◽  
Author(s):  
Y. Y. Liu ◽  
R. M. Parinussa ◽  
W. A. Dorigo ◽  
R. A. M. De Jeu ◽  
W. Wagner ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Land Surface Model ◽  
Cumulative Distribution ◽  
Degree Of Saturation ◽  
Combination Method ◽  
Surface Model ◽  
Volumetric Soil Water Content ◽  
Data Set ◽  
Spatial Coverage

Abstract. Combining information derived from satellite-based passive and active microwave sensors has the potential to offer improved estimates of surface soil moisture at global scale. We develop and evaluate a methodology that takes advantage of the retrieval characteristics of passive (AMSR-E) and active (ASCAT) microwave satellite estimates to produce an improved soil moisture product. First, volumetric soil water content (m3 m−3) from AMSR-E and degree of saturation (%) from ASCAT are rescaled against a reference land surface model data set using a cumulative distribution function matching approach. While this imposes any bias of the reference on the rescaled satellite products, it adjusts them to the same range and preserves the dynamics of original satellite-based products. Comparison with in situ measurements demonstrates that where the correlation coefficient between rescaled AMSR-E and ASCAT is greater than 0.65 ("transitional regions"), merging the different satellite products increases the number of observations while minimally changing the accuracy of soil moisture retrievals. These transitional regions also delineate the boundary between sparsely and moderately vegetated regions where rescaled AMSR-E and ASCAT, respectively, are used for the merged product. Therefore the merged product carries the advantages of better spatial coverage overall and increased number of observations, particularly for the transitional regions. The combination method developed has the potential to be applied to existing microwave satellites as well as to new missions. Accordingly, a long-term global soil moisture dataset can be developed and extended, enhancing basic understanding of the role of soil moisture in the water, energy and carbon cycles.

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