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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2016-658
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
17 Jan 2017
Review status
A revision of this discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
Estimating sediment thickness by using horizontal distance to outcrop as secondary information
Nils-Otto Kitterød 1Norwegian University of Life Sciences, Environmental Sciences and Natural Resource Management, P. Box 5003, N-1432 Ås, Norway
2Norwegian Institute of Bioeconomy Research, Water Resources, P. Box 115, N-1431 Ås, Norway
3Irstea, UR HHLY, Centre de Lyon-Villeurbanne, 5 rue de la Doua BP 32108, F-69626 Villeurbanne Cedex, France
Abstract. Sediment thickness (D) was estimated utilizing a publically available well database from Norway, GRANADA. General challenges associated with such databases typically involve clustering and bias of the data material due to preferential sampling. However, if information about horizontal distance to the nearest outcrop (L) is included, does the spatial estimation of D improve? This idea was tested comparing two cross-validation results: ordinary kriging (OK) where L was disregarded; and co-kriging (CK) where cross-covariance between D and L was included. The analysis resulted in only minor differences between OK and CK in terms of absolute estimation error, however CK produced more precise results than OK. All observations were declustered and transformed to standard normal probability density functions before estimation and back transformed for the cross-validation analysis. The semivariogram analysis gave correlation lengths for D and L of approx. 10 km and 6 km. These correlations reduce the estimation variance in the cross-validation analysis because more than 50 % of the data material had two or more observations within a radius of 5 km. The small-scale variance of D, however, was about 50 % of the total variance, which gave an accuracy of less than 60 % for most of the cross-validation cases. Despite of the noisy character in the data material, the analysis demonstrates that L can be used as a secondary information to reduce the estimation variance of D.

Citation: Kitterød, N.-O.: Estimating sediment thickness by using horizontal distance to outcrop as secondary information, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2016-658, in review, 2017.
Nils-Otto Kitterød
Nils-Otto Kitterød
Nils-Otto Kitterød

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Short summary
The open access database GRANADA (NGU, 2016a) were used to derive point recordings of thickness of sediment above the bedrock D(u). For each D(u) horizontal distance to nearest outcrop L(u) was derived from geological maps. The purpose was to utilize L(u) as a secondary function for estimation of D(u). Two estimation methods were employed: ordinary kriging (OK) and co-kriging (CK). A cross-validation analysis was performed to evaluate the additional information in the secondary function L(u).
The open access database GRANADA (NGU, 2016a) were used to derive point recordings of thickness...
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