A method for identifying optimum strategies of measuring soil water contents for calibrating a root water uptake model

Musters, P.A.D.; Bouten, W.

doi:10.1016/s0022-1694(99)00187-0

Cited by 85 publications

(55 citation statements)

References 14 publications

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“…First, most of the macroscopic parameters cannot be directly determined or measured and, thus, require a calibration. This calibration stage is subject to major limitations: low sensitivity and non-uniqueness of the model parameters, lack of extrapolation power and uncertainty on the measurements used for the calibration (Musters and Bouten, 2000;Hupet and Vanclooster, 2005;Vandoorne et al, 2012). Second, by using root length or mass density distributions, these models neglect the effect of root hydraulic properties and architecture while numerous authors show their significant influence on RWU Schneider et al, 2010).…”

Section: Couvreur Et Al: a Macroscopic Root Water Uptake Model Bamentioning

confidence: 99%

A simple three-dimensional macroscopic root water uptake model based on the hydraulic architecture approach

Couvreur

Vanderborght

Javaux

2012

Hydrol. Earth Syst. Sci.

178

223

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Abstract. Many hydrological models including root water uptake (RWU) do not consider the dimension of root system hydraulic architecture (HA) because explicitly solving water flow in such a complex system is too time consuming. However, they might lack process understanding when basing RWU and plant water stress predictions on functions of variables such as the root length density distribution. On the basis of analytical solutions of water flow in a simple HA, we developed an "implicit" model of the root system HA for simulation of RWU distribution (sink term of Richards' equation) and plant water stress in three-dimensional soil water flow models. The new model has three macroscopic parameters defined at the soil element scale, or at the plant scale, rather than for each segment of the root system architecture: the standard sink fraction distribution SSF , the root system equivalent conductance K rs and the compensatory RWU conductance K comp . It clearly decouples the process of water stress from compensatory RWU, and its structure is appropriate for hydraulic lift simulation. As compared to a model explicitly solving water flow in a realistic maize root system HA, the implicit model showed to be accurate for predicting RWU distribution and plant collar water potential, with one single set of parameters, in dissimilar water dynamics scenarios. For these scenarios, the computing time of the implicit model was a factor 28 to 214 shorter than that of the explicit one. We also provide a new expression for the effective soil water potential sensed by plants in soils with a heterogeneous water potential distribution, which emerged from the implicit model equations. With the proposed implicit model of the root system HA, new concepts are brought which open avenues towards simple and mechanistic RWU models and water stress functions operational for field scale water dynamics simulation.

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Section: Couvreur Et Al: a Macroscopic Root Water Uptake Model Bamentioning

confidence: 99%

A simple three-dimensional macroscopic root water uptake model based on the hydraulic architecture approach

Couvreur

Vanderborght

Javaux

2012

Hydrol. Earth Syst. Sci.

178

223

View full text Add to dashboard Cite

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“…The results of the Monte Carlo runs were also used to determine the information content contained in the observations per parameter (Musters and Bouten, 2000;Vrugt et al, 2001;Weerts et al, 2001). Weerts et al (2001) determined the information content as follows: first, the model is run once using a reference parameter set.…”

Section: Parameter Estimationmentioning

confidence: 99%

Separation of base flow from streamflow using groundwater levels?illustrated for the Pang catchment (UK)

Peters

Lanen

2005

Hydrol. Process.

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Abstract:A new filter to separate base flow from streamflow has developed that uses observed groundwater levels. To relate the base flow to the observed groundwater levels, a non-linear relation was used. This relation is suitable for unconfined aquifers with deep groundwater levels that do not respond to individual rainfall event. Because the filter was calibrated using total streamflow, an estimate of the direct runoff was also needed. The direct runoff was estimated from precipitation and potential evapotranspiration using a water balance model. The parameters for the base flow and direct runoff were estimated simultaneously using a Monte Carlo approach. Instead of one best solution, a range of satisfactory solutions was accepted. The filter was applied to data from two nested gauging stations in the Pang catchment (UK). Streamflow at the upstream station (Frilsham) is strongly dominated by base flow from the main aquifer, whereas at the downstream station (Pangbourne) a significant component of direct runoff also occurs. The filter appeared to provide satisfactory estimates at both stations. For Pangbourne, the rise of the base flow was strongly delayed compared with the rise of the streamflow. However, base flow exceeded streamflow on several occasions, especially during summer and autumn, which might be explained by evapotranspiration from riparian vegetation. To evaluate the results, the base flow was also estimated using three existing base-flow separation filters: an arithmetic filter (BFI), a digital filter (Boughton) and another filter based on groundwater levels (Kliner and Knȇzek). Both the BFI and Boughton filters showed a much smaller difference in base flow between the two stations. The Kliner and Knȇzek filter gave consistently lower estimates of the base flow. Differences and lack of clarity in the definition of base flow complicated the comparison between the filters. An advantage of the method introduced in this paper is the clear interpretation of the separated components. A disadvantage is the high data requirement.

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“…Time-domain reflectometry (TDR) was used to monitor soil moisture, the measuring range being 0-60% volumetric moisture content, and the observed precision 2% (Brandelik & Hubner, 1996;Musters & Bouten, 2000). The WM-1 tensiometers were used to monitor matrix potential (Yan et al, 1994).…”

Section: Sampling Methodsmentioning

confidence: 99%

Bio-geological processes of nitrogen transport and transformation in the aeration zone and aquifer

Zhang

Yang

et al. 2009

Hydrological Sciences Journal

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Nitrate contamination in groundwater originates mainly from excessive use of fertilizers and uncontrolled discharge to land of incompletely-treated wastewater associated with agricultural activities. A systematic field investigation was carried out in a sub-catchment of Dianchi Lake, Kunming, Yunnan, China, into the hydrological, biological and geological processes of nitrogen transport and transformation in the aeration zone and aquifer system. In situ experiments showed that the quantity of NO 3 -N recharged into groundwater was related to fertilization. Nitrification and denitrification behaved quite differently but were affected by moisture content and Eh value. The vertical infiltration rate was controlled by the groundwater table and hydraulic conductivity of the soil. The existence of a zero-flux plane reflected the dynamics of water fluxes in the soil profile and Eh was measured in the aeration zone. In response to these factors, the nitrification rate was greatest in the top soil and reduced with the depth of soil; it was 6.53 mg/(kg·h) in the vegetated plot and 0.2-0.3 mg/(kg·h) in the unvegetated one. The denitrification rate in the unvegetated plot was 6.36 mg/(kg·h), and it was 2.79 mg/(kg·h) in the vegetated one.Key words nitrogen; groundwater; nitrate; nitrification; denitrification Processus bio-géologiques du transport et de la transformation de l'azote en zone non saturée et au sein de l'aquifère Résumé La contamination des eaux souterraines par les nitrates provient essentiellement d'une utilisation excessive de fertilisants et d'un rejet incontrôlé vers le milieu d'eaux usées incomplètement traitées en lien avec les activités agricoles. Une étude de terrain systématique a été menée dans un sous-bassin du bassin versant du Lac Dianchi, Kunming, Yunnan, en Chine, afin de comprendre les processus hydrologiques, biologiques et géologiques déterminants dans le transport et la transformation de l'azote dans la zone non saturée et dans le système aquifère. Des expériences in situ ont montré que la quantité de NO 3 -N apportée par recharge des eaux souterraines est liée à la fertilisation. La nitrification et la dénitrification se comportent très différemment mais sont liées à la teneur en eau et à la valeur de Eh. Le taux d'infiltration verticale est contrôlé par le niveau de la nappe et par la conductivité hydraulique du sol. L'existence d'un plan de flux nul reflète la dynamique des flux hydriques dans le profil de sol et la distribution de Eh dans la zone non saturée, au niveau des sites de mesure. En réponse à ces facteurs, le taux de nitrification est plus fort dans les horizons superficiels et diminue avec la profondeur dans le sol; il s'élève à 6.53 mg/(kg·h) dans la zone végétalisée et à 0.2-0.3 mg/(kg·h) dans la zone non végétalisée. Le taux de dénitrification dans la zone non végétalisée s'élève à 6.36 mg/(kg·h), et à 2.79 mg/(kg·h) dans la zone végétalisée.

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A method for identifying optimum strategies of measuring soil water contents for calibrating a root water uptake model

Cited by 85 publications

References 14 publications

A simple three-dimensional macroscopic root water uptake model based on the hydraulic architecture approach

A simple three-dimensional macroscopic root water uptake model based on the hydraulic architecture approach

Separation of base flow from streamflow using groundwater levels?illustrated for the Pang catchment (UK)

Bio-geological processes of nitrogen transport and transformation in the aeration zone and aquifer

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