Enhancing root-zone soil moisture estimation using Richards' equation and dynamic surface soil moisture data

Root-zone soil moisture (RZSM) is a critical variable for accurately modeling hydrological and ecological processes, but its monitoring is challenging due to the spatial and temporal variability at watershed scales. Richards' equation is a fundamental physical equation that accurately captures...

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Main Authors: Xizhuoma Zha, Wenbin Zhu, Yan Han, Aifeng Lv
Format: Article
Language:English
Published: Elsevier 2025-05-01
Series:Agricultural Water Management
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Online Access:http://www.sciencedirect.com/science/article/pii/S037837742500174X
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author Xizhuoma Zha
Wenbin Zhu
Yan Han
Aifeng Lv
author_facet Xizhuoma Zha
Wenbin Zhu
Yan Han
Aifeng Lv
author_sort Xizhuoma Zha
collection DOAJ
description Root-zone soil moisture (RZSM) is a critical variable for accurately modeling hydrological and ecological processes, but its monitoring is challenging due to the spatial and temporal variability at watershed scales. Richards' equation is a fundamental physical equation that accurately captures the dynamics of soil moisture transport in the root zone. However, due to its high sensitivity to input parameters, its application in large-scale spatial domains remains a significant challenge, particularly in regions with sparse meteorological data. This study addresses these challenges by proposing an innovative approach to estimating root-zone soil moisture by integrating dynamic surface soil moisture data into Richards' equation (SSMRE model). This approach encapsulates soil-atmosphere interactions using near-surface soil moisture, simplifying the computational framework and expanding the applicability of Richards' equation to broader spatial scales. Using the Lightning River Basin as a case study, simulations of different vegetation types and boundary conditions indicate that the correlation coefficient (R) for root zone soil moisture(50 cm) is generally greater than 0.7,SSMRE can accurately simulate root zone soil moisture under various lower boundary conditions and vegetation types. The HYDRUS-1D model, which is widely applied, typically uses atmospheric boundary conditions to simulate soil water movement under atmospheric influence. Comparative analysis of the HYDRUS-1D and SSMRE models against site-measured data reveals that for HYDRUS-1D, the correlation coefficients (R) across 5 cm,10 cm,20 cm,50 cm are 0.654, 0.621, 0.549 and 0.48, with root mean square errors (RMSE) of 0.03, 0.03, 0.03, and 0.04, respectively. The SSMRE model exhibits R values of 0.9, 0.85, 0.74, and 0.72, with RMSE values of 0.04, 0.02, 0.04, and 0.05. Demonstrating that our method provides improved accuracy in root-zone soil moisture simulations. The application of the Shuffled Complex Evolution-University of Arizona (SCE-UA) algorithm significantly enhances the model's accuracy. This research establishes a theoretical foundation for estimating multi-layer soil moisture over large spatial scales by integrating satellite-derived near-surface soil moisture data with Richards' equation.
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spelling doaj-art-944e12bb1d874ecf9c298fdf5ea3b1a92025-08-20T03:10:34ZengElsevierAgricultural Water Management1873-22832025-05-0131210946010.1016/j.agwat.2025.109460Enhancing root-zone soil moisture estimation using Richards' equation and dynamic surface soil moisture dataXizhuoma Zha0Wenbin Zhu1Yan Han2Aifeng Lv3Qinghai Normal University, Qinghai, China; Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, ChinaKey Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, ChinaKey Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, ChinaKey Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China; Corresponding author at: Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.Root-zone soil moisture (RZSM) is a critical variable for accurately modeling hydrological and ecological processes, but its monitoring is challenging due to the spatial and temporal variability at watershed scales. Richards' equation is a fundamental physical equation that accurately captures the dynamics of soil moisture transport in the root zone. However, due to its high sensitivity to input parameters, its application in large-scale spatial domains remains a significant challenge, particularly in regions with sparse meteorological data. This study addresses these challenges by proposing an innovative approach to estimating root-zone soil moisture by integrating dynamic surface soil moisture data into Richards' equation (SSMRE model). This approach encapsulates soil-atmosphere interactions using near-surface soil moisture, simplifying the computational framework and expanding the applicability of Richards' equation to broader spatial scales. Using the Lightning River Basin as a case study, simulations of different vegetation types and boundary conditions indicate that the correlation coefficient (R) for root zone soil moisture(50 cm) is generally greater than 0.7,SSMRE can accurately simulate root zone soil moisture under various lower boundary conditions and vegetation types. The HYDRUS-1D model, which is widely applied, typically uses atmospheric boundary conditions to simulate soil water movement under atmospheric influence. Comparative analysis of the HYDRUS-1D and SSMRE models against site-measured data reveals that for HYDRUS-1D, the correlation coefficients (R) across 5 cm,10 cm,20 cm,50 cm are 0.654, 0.621, 0.549 and 0.48, with root mean square errors (RMSE) of 0.03, 0.03, 0.03, and 0.04, respectively. The SSMRE model exhibits R values of 0.9, 0.85, 0.74, and 0.72, with RMSE values of 0.04, 0.02, 0.04, and 0.05. Demonstrating that our method provides improved accuracy in root-zone soil moisture simulations. The application of the Shuffled Complex Evolution-University of Arizona (SCE-UA) algorithm significantly enhances the model's accuracy. This research establishes a theoretical foundation for estimating multi-layer soil moisture over large spatial scales by integrating satellite-derived near-surface soil moisture data with Richards' equation.http://www.sciencedirect.com/science/article/pii/S037837742500174XHydraulic modelSoil hydraulic property parametersSCE-UA algorithmHYDRUS-1D modelLightning river basin
spellingShingle Xizhuoma Zha
Wenbin Zhu
Yan Han
Aifeng Lv
Enhancing root-zone soil moisture estimation using Richards' equation and dynamic surface soil moisture data
Agricultural Water Management
Hydraulic model
Soil hydraulic property parameters
SCE-UA algorithm
HYDRUS-1D model
Lightning river basin
title Enhancing root-zone soil moisture estimation using Richards' equation and dynamic surface soil moisture data
title_full Enhancing root-zone soil moisture estimation using Richards' equation and dynamic surface soil moisture data
title_fullStr Enhancing root-zone soil moisture estimation using Richards' equation and dynamic surface soil moisture data
title_full_unstemmed Enhancing root-zone soil moisture estimation using Richards' equation and dynamic surface soil moisture data
title_short Enhancing root-zone soil moisture estimation using Richards' equation and dynamic surface soil moisture data
title_sort enhancing root zone soil moisture estimation using richards equation and dynamic surface soil moisture data
topic Hydraulic model
Soil hydraulic property parameters
SCE-UA algorithm
HYDRUS-1D model
Lightning river basin
url http://www.sciencedirect.com/science/article/pii/S037837742500174X
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AT yanhan enhancingrootzonesoilmoistureestimationusingrichardsequationanddynamicsurfacesoilmoisturedata
AT aifenglv enhancingrootzonesoilmoistureestimationusingrichardsequationanddynamicsurfacesoilmoisturedata