Behavior of water balance components at sites with shallow groundwater tables: Possibilities and limitations of their simulation using different ways to control weighable groundwater lysimeters

  • The water cycle of sites with shallow groundwater tables is characterized by complex interactions of hydrological and ecological processes. The water balance components, which are subject to diurnal fluctuations, are best measured with groundwater lysimeters. However, the lower boundary condition of such lysimeters affects most of the hydrological variables, particularly when considering short time scales, and has to be defined in such a way as to facilitate realistic simulations. In this paper, different means of controlling the lower boundary condition of groundwater lysimeters were compared with respect to their ability to simulate the behavior of the water balance components properly. Measurements of rain-free periods from a lysimeter station installed in the Spreewald wetland in north-east Germany were evaluated. The most common groundwater lysimeter type is controlled using a Mariotte bottle and sets the groundwater level in the soil monolith to a constant level, which here caused an alteration of the inflow to the lysimeter,The water cycle of sites with shallow groundwater tables is characterized by complex interactions of hydrological and ecological processes. The water balance components, which are subject to diurnal fluctuations, are best measured with groundwater lysimeters. However, the lower boundary condition of such lysimeters affects most of the hydrological variables, particularly when considering short time scales, and has to be defined in such a way as to facilitate realistic simulations. In this paper, different means of controlling the lower boundary condition of groundwater lysimeters were compared with respect to their ability to simulate the behavior of the water balance components properly. Measurements of rain-free periods from a lysimeter station installed in the Spreewald wetland in north-east Germany were evaluated. The most common groundwater lysimeter type is controlled using a Mariotte bottle and sets the groundwater level in the soil monolith to a constant level, which here caused an alteration of the inflow to the lysimeter, with respect to both its value and diurnal behavior. Still, daily evapotranspiration values were realistic and this simple and robust approach may be used for time intervals not shorter than one day. High-resolution measurements can be gained from lysimeters that automatically adjust the groundwater level by a system of pumps and valves on an hourly basis. Still, reliable results were only obtained when the conditions in the lysimeter and the surrounding field, where the target groundwater level was measured, were in accordance. Otherwise (e.g., when the groundwater level differed) an unrealistic inflow behavior evolved. Reasonable results, even for slightly diverging conditions, were gained with a new approach that defined the lower boundary conditions by controlling the inflows and outflows of the lysimeter. This approach further enabled the groundwater level itself to be the study subject, thereby enlarging the field of possible applications of groundwater lysimeters. (C) 2015 Elsevier B.V. All rights reserved.show moreshow less

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Metadaten
Author:Ottfried Dietrich, Marcus Fahle, Manfred Seyfarth
DOI:https://doi.org/10.1016/j.agwat.2015.09.005
ISSN:0378-3774
ISSN:1873-2283
Parent Title (English):Agricultural water management : an international journal
Publisher:Elsevier
Place of publication:Amsterdam
Document Type:Article
Language:English
Year of first Publication:2016
Year of Completion:2016
Release Date:2020/03/22
Tag:Diurnal fluctuations; Evapotranspiration; Inflow and outflow; Lysimeter control systems; Spreewald wetland; Water storage
Volume:163
Pagenumber:15
First Page:75
Last Page:89
Funder:German Federal Ministry of Education and Science [FKZ: 01LR0803A]; Authority of Environment, Health and Consumer Protection of the Federal State of Brandenburg
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Erd- und Umweltwissenschaften
Peer Review:Referiert