Accounting for Extensive Secondary Information to Improve Watertable Mapping |
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Authors: | M N M Boezio J F C L Costa J C Koppe |
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Institution: | 1. Mining Engineering Department, Federal University of Rio Grande do Sul, Av. Bento Gon?alves, 9500, Bloco IV, Prédio 75, Sala 201, Bairro Agronomia, CEP 91509-900, Porto Alegre, RS, Brazil
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Abstract: | Generally, multiple variables are sampled in addition to the one used to quantify the main phenomenon under study. In some
situations, this secondary information is sampled exhaustively for the study area and can be incorporated for helping in estimating
the variable of interest. There are several methodologies available for incorporating densely sampled secondary information.
Collocated cokriging is one of these methodologies and has the advantage to other methodologies, of accounting for spatial
correlation. However, one drawback in its application comes from the difficulty in modeling the coregionalization. Simplified
models of coregionalization were developed specifically for the collocated cokriging case.
This paper presents, through a case study, the incorporation of dense secondary information using collocated cokriging. The
watertable above a coal underground mine is mapped using water-level readings at monitoring piezometers complemented by highly
correlated topographic data. The incorporation of dense secondary information through the utilization of a linear model of
coregionalization and Markov models is comparatively evaluated in various aspects such as mathematical quality, coherence
with the natural phenomena and the ease of utilization and modeling. Simple kriging with local varying means also is evaluated
as it accounts for nonstationarity and is easily implemented. All these methods that incorporate topography as secondary information
for mapping the watertable provided maps more in accordance with the natural phenomena than ordinary kriging using the principal
attribute solely. Among these methods, strictly collocated cokriging using a linear model of coregionalization showed overall
superior performance. |
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Keywords: | Watertable collocated cokriging coregionalization Markov models local means |
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