Calibration of a Two‐Dimensional Root Water Uptake Model

ISH Journal of Hydraulic Engineering, 2014

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Reviews of Geophysics, 2012

RG3003 comprises aquifers and cave ecosystems, where species such as crustaceans, insects, worms, fishes, and microscopic organisms can be found [Humphreys, 2006; Tomlinson and Boulton, 2010]. The second class includes springs, wetlands, rivers, estuaries, and nearshore marine ecosystems. The third class primarily consists of terrestrial vegetation, which is a term meant to exclude aquatic, submerged, and emergent vegetation [Eamus et al., 2006b] and associated faunal, microbial, and fungal populations. [4] This review focuses on the vegetation belonging to the third class, and specifically on phreatophytes, defined here as plants that have roots that can penetrate the capillary fringe and the saturated zone [Naumburg et al., 2005]. Perhaps the most thorough studies on the subject yet remain the reports from the U.S. Geological Survey by Meinzer [1927], White [1932], and Robinson [1958]. Meinzer [1927] reviews phreatophyte species mainly present in the western United States, identifying their main characteristics in relation to groundwater depth; this report was updated by Robinson [1958]. White [1932] presents results from experiments in Utah to show how transpiration generates daily groundwater fluctuations, which can be used to estimate plant groundwater use. More recently, Le Maitre et al. [1999] reviewed studies in South Africa and Australia, and Naumburg et al. [2005] described the consequences of water table fluctuations on water use by phreatophytes. Eamus et al. [2006b] present details of studies of GDEs in four catchments throughout Australia and a general introduction of GDEs and their management in South Africa. Lubczynski [2009] discussed experimental methods to estimate vegetation groundwater use at different time and spatial scales and provided information about existent models that include the interaction between groundwater and vegetation. In addition to these reviews, which focus more on deep groundwater environments, Rodriguez-Iturbe et al. [2007] summarized the main feedback mechanisms between vegetation and water table depth in shallow groundwater ecosystems and wetlands. Although we will not focus specifically on wetlands, because that would widen too much the scope of this review, several riparian ecosystems in arid and semiarid climates experience shallow groundwater levels and are thus pertinent to our discussion. [5] In summary, in this review we try to guide readers through the ample literature on phreatophytes from different fields, including ecology, plant physiology, and hydrology. We review the mechanisms that allow phreatophytes to use groundwater and how different water table levels might induce vegetation patterns and thus shape the landscape. A description of the main quantitative models developed to simulate the interactions between vegetation and groundwater dynamics is also presented. Research gaps are identified and possible directions to deepen the knowledge of GDEs and improve their management are suggested.

Water Resources Research, 2003

In this paper we have tested the feasibility of the inverse modeling approach to derive root water uptake parameters (RWUP) from soil water content data using numerical experiments for three differently textured soils and for an optimal drying period. The RWUP of interest are the rooting depth and the bottom root length density. In a first step, a thorough sensitivity analysis was performed. This showed that soil water content dynamics is relatively insensitive to RWUP and that the sensitivity depends on the texture of the considered soil. For medium-fine textured soil, the sensitivity is particularly low due to relatively high unsaturated hydraulic conductivity values. These ones allow a ''compensating effect'' to occur, i.e., vertical unsaturated water fluxes overshadowing in some way the root water uptake. In a second step, we analyzed the well-posedness of the solution (stability and nonuniqueness) when only RWUP are optimized. For this case, the inverse problem is clearly ill-posed except for the estimation of the rooting depth parameter for coarse and the very fine textured soils. In a third step, we addressed the case where RWUP are estimated simultaneously with additional parameters of the system (i.e., with soil hydraulic parameters). For this case, our study showed that the inverse problem is well-posed for the coarse and very fine textured soils, allowing for the estimation of both RWUP of interest provided that a powerful global optimization algorithm is used. On the contrary, the estimation of RWUP is unfeasible for medium-fine textured soil due to the ''compensating effect'' of the vertical unsaturated water flows. In conclusion, we can state that the inverse modeling approach can be applied to derive RWUP for some soils (coarse and very fine textured) and that the feasibility is strongly improved if the RWUP are simultaneously optimized with additional parameters. Nevertheless, more detailed research is needed to apply the inverse modeling approach to real cases for which additional issues are likely to be encountered such as soil heterogeneity and root dynamics.

Hydrological Processes, 2011

When hydrology model parameters are determined, a traditional data assimilation method (such as Kalman filter) and a hydrology model can estimate the root zone soil water with uncertain state variables (such as initial soil water content). The simulated result can be quite good. However, when a key soil hydraulic property, such as the saturated hydraulic conductivity, is overestimated or underestimated, the traditional soil water assimilation process will produce a persistent bias in its predictions. In this paper, we present and demonstrate a new multi-scale assimilation method by combining the direct insertion assimilation method, particle swarm optimisation (PSO) algorithm and Richards equation. We study the possibility of estimating root zone soil water with a multi-scale assimilation method by using observed in situ data from the Wudaogou experiment station, Huaihe River Basin, China. The results indicate there is a persistent bias between simulated and observed values when the direct insertion assimilation surface soil water content is used to estimate root zone soil water contents. Using a multi-scale assimilation method (PSO algorithm and direct insertion assimilation) and an assumed bottom boundary condition, the results show some obvious improvement, but the root mean square error is still relatively large. When the bottom boundary condition is similar to the actual situation, the multi-scale assimilation method can well represent the root zone soil water content. The results indicate that the method is useful in estimating root zone soil water when available soil water data are limited to the surface layer and the initial soil water content even when the soil hydraulic conductivities are uncertain.

Hydrological Processes, 2010

Root zone soil water content impacts plant water availability, land energy and water balances. Because of unknown hydrological model error, observation errors and the statistical characteristics of the errors, the widely used Kalman filter (KF) and its extensions are challenged to retrieve the root zone soil water content using the surface soil water content. If the soil hydraulic parameters are poorly estimated, the KF and its extensions fail to accurately estimate the root zone soil water. The H-infinity filter (HF) represents a robust version of the KF. The HF is widely used in data assimilation and is superior to the KF, especially when the performance of the model is not well understood. The objective of this study is to study the impact of uncertain soil hydraulic parameters, initial soil moisture content and observation period on the ability of HF assimilation to predict in situ soil water content. In this article, we study seven cases. The results show that the soil hydraulic parameters hold a critical role in the course of assimilation. When the soil hydraulic parameters are poorly estimated, an accurate estimation of root soil water content cannot be retrieved by the HF assimilation approach. When the estimated soil hydraulic parameters are similar to actual values, the soil water content at various depths can be accurately retrieved by the HF assimilation. The HF assimilation is not very sensitive to the initial soil water content, and the impact of the initial soil water content on the assimilation scheme can be eliminated after about 5-7 days. The observation interval is important for soil water profile distribution retrieval with the HF, and the shorter the observation interval, the shorter the time required to achieve actual soil water content. However, the retrieval results are not very accurate at a depth of 100 cm. Also it is complex to determine the weighting coefficient and the error attenuation parameter in the HF assimilation. In this article, the trial-and-error method was used to determine the weighting coefficient and the error attenuation parameter. After the first establishment of limited range of the parameters, 'the best parameter set' was selected from the range of values. For the soil conditions investigated, the HF assimilation results are better than the open-loop results.

2021

Abstract. The biophysical processes occurring in the unsaturated zone have a direct impact on the water table dynamics. Representing these processes through the application of unsaturated zone models of different complexity has an impact on the estimates of the volumes of water flowing between the unsaturated zone and the aquifer. These fluxes, known as net recharge, are often used as the shared variable that couples unsaturated to groundwater models. However, as recharge estimates are always affected by a degree of uncertainty, model–data fusion methods, such as data assimilation, can be used to inform these coupled models and reduce uncertainty. This study assesses the effect of unsaturated zone models complexity (conceptual versus physically based) to update groundwater model outputs, through the assimilation of actual evapotranspiration rates, for a water-limited site in South Australia. Actual evapotranspiration rates are assimilated because they have been shown to be related t...

Irrigation Science, 2015

scenarios with plastic and irrigation in alternate furrows showed a reduction in transpiration and yield, more water loss due to deep drainage, and less water lost due to evaporation. However, similar crop yields were obtained for this alternate furrow strategy as for the control furrow surface treatments. When only half the water was used for irrigation in this scenario, the reduction in yield was less than 20 % compared to the control treatments, producing higher water-use efficiency. Communicated by J. Hornbuckle.

Water, 2019

This paper mainly aims to illustrate an irrigation management tool to simulate scheduling of district-level water needs over the course of an irrigation season. The tool is mostly based on a daily model for simulating flow of water (and solutes) in heterogeneous agri-environmental systems (called FLOWS-HAGES). The model produces information on the daily evolution of: soil water contents and pressure potentials in the soil profile; water uptake and actual evapotranspiration; stress periods for each crop; return fluxes to the groundwater and their quality in terms of solute concentrations (e.g., nitrates). FLOWS-HAGES provides a daily list of hydrants to be operated according to water or crop-based criteria. The daily optimal sequence of hydrant use may thus be established by passing the volumes to be delivered on to the model for simulating the hydraulics of the irrigation network, in order to ensure that the discharges flowing inside the network of distribution pipes are delivered under optimal pressure head distribution in the system. All the above evaluations can be carried out in a stochastic framework to account for soil heterogeneity and climate changes. To illustrate the potential of FLOWS-HAGES, a case study was considered for a selected sector of the Irrigation District 10 in the "Sinistra Ofanto" irrigation system (southern Italy, Apulia region). In a 139 ha area (Sector 6 of the Irrigation District), soil profiles were analyzed for characterization of hydraulic properties variability. Hydraulic properties were determined by a combination of field and laboratory measurements. Model simulations were validated by comparing soil water storage simulated and measured by a sensor based on electromagnetic induction technique. Irrigation water volumes and frequency calculated by the model were compared to the volumes actually supplied by the farmers. Compared to the farmers behavior, the model simulates more frequent irrigations with lower irrigation volumes. Finally, some indexes of irrigation performance were calculated for each farm under study. The resulting maps provide useful information on the spatial distribution of farmer behavior, indicating the abuse or underuse of water as well as the fraction of the water lost by drainage following the irrigation method applied.

Vadose Zone Journal, 2021

Turfgrass systems have been identified as potential sources of nitrate leaching and subsequent groundwater contamination. The HYDRUS (2D/3D) model was used to quantify nitrate leaching from bermudagrass [Cynodon dactylon (L.) Pers.] and buffalograss [Buchloe dactyloides (Nutt.) Engelm] established by either seed or sod and irrigated with either tailored (defined as reclaimed water with an N concentration of 15 mg L -1 ) or potable water and fertilized with calcium nitrate. A parameter sensitivity analysis conducted prior to model calibration revealed that soil texture, denitrification rate, and plant uptake all affected nitrate leaching. Simulated nitrate flux matched the experimental data more accurately when denitrification rate varied by soil depth. Moreover, nitrate leaching also differed between turfgrass species and between establishment methods. Leaching was higher from grasses propagated by seed than from sod at the beginning of the establishment period. Increasing the concentration of nitrate in tailored water from 0 to 200 mg L -1 increased concentrations at 50-cm depths for both species but the increase was significantly higher under buffalograss than bermudagrass and was attributed to lower nutrient uptake and denitrification rates under buffalograss. Nitrate concentrations at 50-cm depth were significantly higher for coarse sand compared with loamy sand, which was attributed to differences in retention times of the two soil types. Soil texture was even more important than nitrate application rate in predicting nitrate leaching losses and the results of the sensitivity analysis demonstrated that nitrate leaching was affected more by denitrification than by plant uptake. Turfgrass systems, which generally require regular irrigation and N fertilizer applications, are increasingly being scrutinized as a potential source of NO 3 -N leaching (Carey et al., Abbreviations: CSS, composite scale sensitivities; LAI, leaf area index. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Water Resources Research, 2001

Although solutions of multidimensional transient water flow can be obtained by numerical modeling, their application may be limited as root water uptake is generally considered to be one-or two-dimensional only. This is especially the case for trees. The first objective of this paper is to test the suitability of a three-dimensional root water uptake model for the simultaneous simulation of transient soil water flow around an almond tree. The soil hydraulic and root water uptake parameters were optimized by minimizing the residuals between measured and simulated water content data. Water content was measured in a three-dimensional grid around a sprinkler-irrigated almond tree for a 16 day period, following irrigation. A second objective was to compare the performance and results of the three-dimensional flow model with one-and twodimensional root water uptake models. For this purpose, measured water contents were aggregated in the x and y direction in the one-dimensional case and in the radial direction for the two-dimensional uptake model. For the estimation of root water uptake model parameters a genetic algorithm was used to estimate the approximate global minimum of the parameter space, whereas final parameters were determined using the Simplex optimization algorithm. With the optimized root water uptake parameters, simulated and measured water contents during the 16-day period were in excellent agreement for all root water uptake models. Most significantly, the spatial variation in flux density below the rooting zone decreased when reducing multidimensional root water uptake to fewer dimensions, thereby justifying the proposed multidimensional approach.

Revista Iberoamericana de Automática e Informática industrial

En la agricultura que se desarrolla en los valles cordilleranos de Argentina, el uso eficiente del agua destinada para el riego es fundamental para el desarrollo y sustentabilidad de los emprendimientos agrícolas. A fin de abordar este desafío, se propone lograr un modelo híbrido que permita representar con la mayor fidelidad posible la dinámica del contenido de agua en un suelo bajo riego por goteo, incluyendo la extracción de agua por parte de un cultivo. Para esto, se cuenta con la formulación de un modelo matemático del proceso basado en la ecuación general de flujo, la cual ha sido resuelta mediante diferencias finitas. Se incorpora a esta estructura una red neuronal de base radial (RBF) para compensar de manera off-line la salida del modelo en un punto del suelo, identificando el error de salida. Además, este estudio incorpora el diseño de un controlador de riego de tipo adaptable para dinámicas desconocidas. El diseño está basado en superficies deslizantes en combinación PI ...

Irrigation and Drainage, 2015

Agriculture constitutes the backbone of Pakistan's economy by contributing 21.4% to national gross domestic product. 74% of cultivated area is irrigated (14.6 million hectares), out of 22 million hectares. Per capita water availability in Pakistan is continuously on decline as it stood at 1000 cubic meter per person per year in 2012-13, against 5600 cubic meter per person per year at the time of partition. Agricultural water availability is dwindling with each passing year, particularly due to reduction in Pakistan's water storage capacity, increasing population and climate change. Pakistan owns world's largest irrigation system as total length of canals in Pakistan is 56073 km, while the total length of water courses is 1.6 million km. About, 106 million acre feet water is diverted to canals, of which about 15% is lost in main and branch canals, 8% water is lost in distributary minors and 30% water is lost in water courses and 30% in the field, thus making the efficiency of irrigation system just over 41%. Drip irrigation also known as trickle irrigation which involves dripping water onto the soil at very low rates (2-20 liters per hour) constitutes the future life line for Pakistan's irrigated agriculture. But high initial cost in the range of Rs.110000-120000 per acre and lack of awareness has hampered the adoption of this technique. Government needs to shoulder the responsibility by subsidizing the initial cost for drip irrigation to ensure the food security of teeming millions in times to come.

Water Resources Research, 2008

We explore and review the value of soil moisture measurements in vadose zone hydrology with a focus on the field and catchment scales. This review is motivated by the increasing ability to measure soil moisture with unprecedented spatial and temporal resolution across scales. We highlight and review the state of the art in using soil moisture measurements for (1) estimation of soil hydraulic properties, (2) quantification of water and energy fluxes, and (3) retrieval of spatial and temporal dynamics of soil moisture profiles. We argue for the urgent need to have access to field monitoring sites and databases that include detailed information about variability of hydrological fluxes and parameters, including their upscaled values. In addition, improved data assimilation methods are needed that fully exploit the information contained in soil moisture data. The development of novel upscaling methods for predicting effective moisture fluxes and disaggregation schemes toward integrating large-scale soil moisture measurements in hydrological models will increase the value of soil moisture measurements. Finally, we recognize a need to develop strategies that combine hydrogeophysical measurement techniques with remote sensing methods.

Irrigation Science

The main purpose of this paper was to study the effect of spatial variability of soil hydraulic properties (HP) and vegetation parameters (VP) (e.g., leaf-area index, LAI, and crop coefficient, Kc) on modelling agro-hydrological processes and optimising irrigation volumes at large scale. Based on this analysis, the effect of partly overlooking the spatial variability of soil HP and/or VP inputs was verified on a 140 ha irrigation sector in “Sinistra Ofanto” irrigation system in Apulia Region, Southern Italy. Five soil profiles were excavated and the HP were measured in all the soil horizons. Additionally, measurements of soil HP were taken in the surface soil layer in ninety sites distributed over the whole irrigation sector. All the HP measurements were carried out using tension infiltrometer. Remote sensing applications were used to obtain LAI and Kc using European Space Agency’s (ESA) Sentinel-2 images with 10 m resolutions. First, distributed (on ninety polygons with an average ...

Water Resources Management

In this study, wetting patterns around the reservoirs with different permeability (low, medium, and high) were assessed in the eld and simulated using the HYDRUS-2D/3D software. The results showed that the highest soil water content was observed near the reservoir and it decreased with increasing distance from the reservoir. In the high permeability treatment, a large volume of water was released for almost three days, so that, more water was deep-percolated and lowered the soil water available to plant roots. In the low and medium permeability treatments, the water content slowly moved and observed that the maximum soil water content occurred in the 20-40 cm layer overtime. The HYDRUS-2D/3D software was able to simulate water ow and soil water content during the growth period of plants with a high correspondence between measured and simulated soil water contents (R 2 = 0.90-0.95). 1 Introduction Water scarcity in the arid and semi-arid regions is a major concern. High-performance irrigation systems, such as surface or subsurface drip irrigation systems, are often recommended to overcome this problem and to dramatically increase the water use e ciency over that of traditional irrigation systems (Kandelous and Šimůnek, 2010). Subsurface irrigation with a ring-shaped emitter is one of the irrigation techniques in arid lands. Emitters are usually made from rubber although ring-shaped emitters have been successfully used for irrigation; its current design and operation are purely empirical. Besides, the current design of the ring-shaped emitter does not allow one to easily detect malfunctions because the emitter is fully covered with a permeable textile. As a result, it is not easy to repair it quickly (Saefuddin et al., 2019). Transient simulation models allow one to consider the physical processes governing the ow of water and chemicals in the unsaturated root-soil zone and consequently to evaluate the shape and the dimension of the wetting patterns as a function of the amount of applied water. The knowledge of the wetted soil volume dimensions as a function of time contributes, for each soil type, to identify proper design parameters (emitter spacing and distance between laterals) and the duration of irrigation providing to wet a xed soil depth (Provenzano, 2007). Deterministic models de ne mathematically individual processes as well as interactions between them, and each set of input data leading to a unique and reproducible prediction (Šimůnek et al., 1999; Wagenet and Hutson, 1992). Using physically based simulation models also contributes to develop management scenarios and strategies for irrigation, aiming to nd indications for water saving and consequently for increasing water use e ciency. To assess the accuracy of the models, it is necessary to proceed for the calibration and validation by using experimental measurements (Provenzano, 2007).

Water, 2023

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