Grundvattenpotential i Västerviks kommun : Geostatistiska metoder i en GIS-miljö

Sammanfattning: In this study, groundwater resource potential (GRP) for Västervik municipality has been investigated using the methodology developed in the article by Earon et al. (2015). The aim was to test the reliability of the methodology for groundwater mapping, as to further add to the knowledge base of groundwater access. The GRP-methodology is a linear additive multicriteria analysis where geohydrological indicators are scored, classified into groups, then multiplied by weights calculated using Principal Component Analysis (PCA). The classification and validation were performed against specific capacity [L/(h'm)], which is a well's capacity calculated at drilling, per meter well. GRP was calculated in different sets based on 13 geohydrological variables such as altitude and Topographic Wetness Index (TWI). The results included correlation tests for Kendall's tau (0.06-0.13), Spearmans rho (0.09-0.19) with a total accuracy of 52-55%. Positive but low values ​​for Cohen´s kappa indicated that all calculations performed better than a random generator, but not by margin. Calculations of VIP (Variables importance on PLS projection), based on Partial Least Squares (PLS), identified Altitude, Earth type, Drainage density and TWI as the most influential indicators for the analysis.The conclusions of this study were, among other things, that the GRP methodology had low predictivity due to the weak relationships between the indicators and the specific capacity. The weaknesses could also be due to the fact that specific capacity has weaknesses as a validation variable for groundwater resource potential linked to uncertainties of the capacity measured at wellbore. The study shows that further development of the weighting scheme by integrating PLS would be beneficial, as PLS calculates the variance of the indicators based on the specific capacity, instead of assuming it as a PCA.