Testing alternative uses of electromagnetic data to reduce the prediction error of groundwater models

Persistent Link:
http://hdl.handle.net/10150/617369
Title:
Testing alternative uses of electromagnetic data to reduce the prediction error of groundwater models
Author:
Christensen, Nikolaj Kruse; Christensen, Steen; Ferre, Ty Paul A.
Affiliation:
Univ Arizona, Dept Hydrol & Water Resources
Issue Date:
2016-05-13
Publisher:
COPERNICUS GESELLSCHAFT MBH
Citation:
Testing alternative uses of electromagnetic data to reduce the prediction error of groundwater models 2016, 20 (5):1925 Hydrology and Earth System Sciences
Journal:
Hydrology and Earth System Sciences
Rights:
© Author(s) 2016. CC Attribution 3.0 License.
Collection Information:
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.
Abstract:
In spite of geophysics being used increasingly, it is often unclear how and when the integration of geophysical data and models can best improve the construction and predictive capability of groundwater models. This paper uses a newly developed HYdrogeophysical TEst-Bench (HYTEB) that is a collection of geological, groundwater and geophysical modeling and inversion software to demonstrate alternative uses of electromagnetic (EM) data for groundwater modeling in a hydrogeological environment consisting of various types of glacial deposits with typical hydraulic conductivities and electrical resistivities covering impermeable bedrock with low resistivity (clay). The synthetic 3-D reference system is designed so that there is a perfect relationship between hydraulic conductivity and electrical resistivity. For this system it is investigated to what extent groundwater model calibration and, often more importantly, model predictions can be improved by including in the calibration process electrical resistivity estimates obtained from TEM data. In all calibration cases, the hydraulic conductivity field is highly parameterized and the estimation is stabilized by (in most cases) geophysics-based regularization.<br><br> For the studied system and inversion approaches it is found that resistivities estimated by sequential hydrogeophysical inversion (SHI) or joint hydrogeophysical inversion (JHI) should be used with caution as estimators of hydraulic conductivity or as regularization means for subsequent hydrological inversion. The limited groundwater model improvement obtained by using the geophysical data probably mainly arises from the way these data are used here: the alternative inversion approaches propagate geophysical estimation errors into the hydrologic model parameters. It was expected that JHI would compensate for this, but the hydrologic data were apparently insufficient to secure such compensation. With respect to reducing model prediction error, it depends on the type of prediction whether it has value to include geophysics in a joint or sequential hydrogeophysical model calibration. It is found that all calibrated models are good predictors of hydraulic head. When the stress situation is changed from that of the hydrologic calibration data, then all models make biased predictions of head change. All calibrated models turn out to be very poor predictors of the pumping well's recharge area and groundwater age. The reason for this is that distributed recharge is parameterized as depending on estimated hydraulic conductivity of the upper model layer, which tends to be underestimated. Another important insight from our analysis is thus that either recharge should be parameterized and estimated in a different way, or other types of data should be added to better constrain the recharge estimates.
Note:
Open access.
ISSN:
1607-7938
DOI:
10.5194/hess-20-1925-2016
Version:
Final published version
Sponsors:
HyGEM, Integrating geophysics, geology, and hydrology [11-116763]; Danish Council for Strategic Research
Additional Links:
http://www.hydrol-earth-syst-sci.net/20/1925/2016/

Full metadata record

DC FieldValue Language
dc.contributor.authorChristensen, Nikolaj Kruseen
dc.contributor.authorChristensen, Steenen
dc.contributor.authorFerre, Ty Paul A.en
dc.date.accessioned2016-07-22T23:58:22Z-
dc.date.available2016-07-22T23:58:22Z-
dc.date.issued2016-05-13-
dc.identifier.citationTesting alternative uses of electromagnetic data to reduce the prediction error of groundwater models 2016, 20 (5):1925 Hydrology and Earth System Sciencesen
dc.identifier.issn1607-7938-
dc.identifier.doi10.5194/hess-20-1925-2016-
dc.identifier.urihttp://hdl.handle.net/10150/617369-
dc.description.abstractIn spite of geophysics being used increasingly, it is often unclear how and when the integration of geophysical data and models can best improve the construction and predictive capability of groundwater models. This paper uses a newly developed HYdrogeophysical TEst-Bench (HYTEB) that is a collection of geological, groundwater and geophysical modeling and inversion software to demonstrate alternative uses of electromagnetic (EM) data for groundwater modeling in a hydrogeological environment consisting of various types of glacial deposits with typical hydraulic conductivities and electrical resistivities covering impermeable bedrock with low resistivity (clay). The synthetic 3-D reference system is designed so that there is a perfect relationship between hydraulic conductivity and electrical resistivity. For this system it is investigated to what extent groundwater model calibration and, often more importantly, model predictions can be improved by including in the calibration process electrical resistivity estimates obtained from TEM data. In all calibration cases, the hydraulic conductivity field is highly parameterized and the estimation is stabilized by (in most cases) geophysics-based regularization.<br><br> For the studied system and inversion approaches it is found that resistivities estimated by sequential hydrogeophysical inversion (SHI) or joint hydrogeophysical inversion (JHI) should be used with caution as estimators of hydraulic conductivity or as regularization means for subsequent hydrological inversion. The limited groundwater model improvement obtained by using the geophysical data probably mainly arises from the way these data are used here: the alternative inversion approaches propagate geophysical estimation errors into the hydrologic model parameters. It was expected that JHI would compensate for this, but the hydrologic data were apparently insufficient to secure such compensation. With respect to reducing model prediction error, it depends on the type of prediction whether it has value to include geophysics in a joint or sequential hydrogeophysical model calibration. It is found that all calibrated models are good predictors of hydraulic head. When the stress situation is changed from that of the hydrologic calibration data, then all models make biased predictions of head change. All calibrated models turn out to be very poor predictors of the pumping well's recharge area and groundwater age. The reason for this is that distributed recharge is parameterized as depending on estimated hydraulic conductivity of the upper model layer, which tends to be underestimated. Another important insight from our analysis is thus that either recharge should be parameterized and estimated in a different way, or other types of data should be added to better constrain the recharge estimates.en
dc.description.sponsorshipHyGEM, Integrating geophysics, geology, and hydrology [11-116763]; Danish Council for Strategic Researchen
dc.language.isoenen
dc.publisherCOPERNICUS GESELLSCHAFT MBHen
dc.relation.urlhttp://www.hydrol-earth-syst-sci.net/20/1925/2016/en
dc.rights© Author(s) 2016. CC Attribution 3.0 License.en
dc.titleTesting alternative uses of electromagnetic data to reduce the prediction error of groundwater modelsen
dc.typeArticleen
dc.contributor.departmentUniv Arizona, Dept Hydrol & Water Resourcesen
dc.identifier.journalHydrology and Earth System Sciencesen
dc.description.noteOpen access.en
dc.description.collectioninformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.en
dc.eprint.versionFinal published versionen
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