Print Email Facebook Twitter Identification and Explanation of a Change in the Groundwater Regime using Time Series Analysis Title Identification and Explanation of a Change in the Groundwater Regime using Time Series Analysis Author Obergfell, C.C.A. (TU Delft Water Resources) Bakker, M. (TU Delft Water Resources) Maas, C. (Maas Geohydrologisch Advies) Date 2019 Abstract Time series analysis is applied to identify and analyze a transition in the groundwater regime in the aquifer below the sand ridge of Salland in the Netherlands, where groundwater regime refers to the range of head variations throughout the seasons. Standard time series analysis revealed a discrepancy between modeled and observed heads in several piezometers indicating a possible change in the groundwater regime. A new time series modeling approach is developed to simulate the transition from the initial regime to the altered regime. The transition is modeled as a weighted sum of two responses, one representing the initial state of the system, the other representing the altered state. The inferred timing and magnitude of the change provided strong evidence that the transition was the result of significant dredging works that increased the river bed conductance of the main river draining the aquifer. The plausibility of this explanation is corroborated by an analytical model. This case study and the developed approach to identify a change in the groundwater regime are meant to stimulate a more systematic application of time series analysis to detect and understand changes in groundwater systems which may easily go unnoticed in groundwater flow modeling. To reference this document use: http://resolver.tudelft.nl/uuid:c7700681-bfdf-4c2d-9580-0a190bf49dc2 DOI https://doi.org/10.1111/gwat.12891 ISSN 0017-467X Source Groundwater, 57 (6), 886-894 Part of collection Institutional Repository Document type journal article Rights © 2019 C.C.A. Obergfell, M. Bakker, C. Maas Files PDF Obergfell_et_al_2019_Grou ... ater_1.pdf 1.2 MB Close viewer /islandora/object/uuid:c7700681-bfdf-4c2d-9580-0a190bf49dc2/datastream/OBJ/view