University of Twente Student Theses


A comparison of groundwater level estimation methods

Dekker, L.P. (2023) A comparison of groundwater level estimation methods.

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Abstract:Inundation models, which serve to estimate the risk of damage as a result of pluvial floods, rely on a large number of input parameters. One of the most important ones is available soil storage, which is in turn very dependent on groundwater level. There are various different methods to estimate groundwater level. In this research, four of these are compared in order to assess/evaluate their strengths and weaknesses. The main research question is: Which sources of groundwater level are most accurate under which circumstances? To address this overarching question, two sub-questions have been formulated: 1) Which hydrological conditions are responsible for/influence the deviations between the estimates? 2) How can the identified deviations be explained through the sources' calculation method? The four groundwater sources assessed were WDM, LHM, Alterra and Acacia. WDM and Alterra are interpolations of measured values, while LHM and Acacia are complete, complex hydrological models, which describe the flow of water in the soil. The outputs of these sources is expressed in terms of mean lowest water table (MLW) and mean highest water table MHW), which correspond to the lower and upper bound of the annual trend line of the water table in any specific location. Together, these parameters are called MxW. The study area is the territory of Hoogheemraadschap Hollands Noorderkwartier, one of the 21 water authorities of the Netherlands. The study’s results show, among other things, that in the higher sandy areas the measurement-based sources, WDM and Alterra, give too shallow estimates of the groundwater level because the estimates depend on measurements taken outside of the study area. Moreover, these sources overestimate the depth of the MHW in peaty areas, in the south of the study area. This is likely caused by the linear regression used. In addition, it was shown that the measurement-based sources are generally closest to the genuine values, but do not portray the variation of the groundwater level with respect to the surface through space as well as the simulation-based sources do. This makes sense because the measurement-based sources only use measured (so realistic) values, but describe the whole area based on these measurement locations, despite the fact that they could be subject to local, special circumstances. Conversely, however, the simulation-based sources do have extreme, unreliable values in more locations, LHM has a too shallow MHW estimate on the island of Texel and Acacia varies too extremely on a local level.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Programme:Civil Engineering BSc (56952)
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