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Factor weighting in DRASTIC modeling

Pacheco, F.A.L. ; Pires, L.M.G.R. ; Santos, R.M.B. ; Sanches Fernandes, L.F.

The Science of the total environment, 2015-02, Vol.505, p.474-486 [Periódico revisado por pares]

Netherlands: Elsevier B.V

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  • Título:
    Factor weighting in DRASTIC modeling
  • Autor: Pacheco, F.A.L. ; Pires, L.M.G.R. ; Santos, R.M.B. ; Sanches Fernandes, L.F.
  • Assuntos: Adjustment ; Aquifers ; Correspondence Analysis ; DRASTIC aquifer vulnerability model ; Factor weighting ; Hydrology ; Logistic Regression ; Mathematical models ; Regression ; Sensitivity Analysis ; Spearman rank-order correlation ; Texture ; Weighting
  • É parte de: The Science of the total environment, 2015-02, Vol.505, p.474-486
  • Notas: ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
    content type line 23
  • Descrição: Evaluation of aquifer vulnerability comprehends the integration of very diverse data, including soil characteristics (texture), hydrologic settings (recharge), aquifer properties (hydraulic conductivity), environmental parameters (relief), and ground water quality (nitrate contamination). It is therefore a multi-geosphere problem to be handled by a multidisciplinary team. The DRASTIC model remains the most popular technique in use for aquifer vulnerability assessments. The algorithm calculates an intrinsic vulnerability index based on a weighted addition of seven factors. In many studies, the method is subject to adjustments, especially in the factor weights, to meet the particularities of the studied regions. However, adjustments made by different techniques may lead to markedly different vulnerabilities and hence to insecurity in the selection of an appropriate technique. This paper reports the comparison of 5 weighting techniques, an enterprise not attempted before. The studied area comprises 26 aquifer systems located in Portugal. The tested approaches include: the Delphi consensus (original DRASTIC, used as reference), Sensitivity Analysis, Spearman correlations, Logistic Regression and Correspondence Analysis (used as adjustment techniques). In all cases but Sensitivity Analysis, adjustment techniques have privileged the factors representing soil characteristics, hydrologic settings, aquifer properties and environmental parameters, by leveling their weights to ≈4.4, and have subordinated the factors describing the aquifer media by downgrading their weights to ≈1.5. Logistic Regression predicts the highest and Sensitivity Analysis the lowest vulnerabilities. Overall, the vulnerability indices may be separated by a maximum value of 51 points. This represents an uncertainty of 2.5 vulnerability classes, because they are 20 points wide. Given this ambiguity, the selection of a weighting technique to integrate a vulnerability index may require additional expertise to be set up satisfactorily. Following a general criterion that weights must be proportional to the range of the ratings, Correspondence Analysis may be recommended as the best adjustment technique. •Compare techniques of factor weighting in DRASTIC modeling•Evaluate the impact of changing the weighting technique on the vulnerability index•Model the vulnerability of a large group of aquifer systems in continental Portugal
  • Editor: Netherlands: Elsevier B.V
  • Idioma: Inglês
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