Journal of Hydraulic Structures

Journal of Hydraulic Structures

Geostatistical Analysis of Groundwater Levels at Tangab Dam Using IDW, Kriging, and Sequential Gaussian Simulation

Document Type : Research Paper

Authors
Reza Dehshibi 1
Hadi Farhadian 2
1 Department of Engineering, University of Sistan & Baluchestan, Zahedan, Iran.
2 Department of Mining Engineering, Faculty of Engineering, University of Birjand, Birjand, Iran
10.22055/jhs.2025.49615.1350
Abstract
Monitoring groundwater levels at every point in dam abutments is often impractical; hence, geostatistical interpolation methods offer a viable alternative. This study applied inverse distance weighting (IDW), kriging, and sequential Gaussian simulation (SGS) to estimate groundwater levels at the Tangab Dam, based on data from 49 piezometers. After data normalization, variogram modeling identified the spherical model as the best fit, with a nugget-to-sill ratio of 19%, indicating strong spatial continuity. While IDW served for initial visualization, kriging and SGS revealed higher groundwater levels along the dam’s right abutment, corresponding to fault zones and karst features. The SGS approach, performed through 100 realizations, accurately reproduced the spatial variability and statistical properties of the observed data. Validation showed a correlation coefficient of 0.93 and unbiased residuals, confirming the model's reliability in well-instrumented regions. However, estimations in the northeastern and eastern zones were less reliable due to sparse data. This study underscores the value of integrating geostatistics and geological context for characterizing groundwater behavior in complex karst environments. Future work should involve expanding the monitoring network and coupling geostatistical outputs with numerical flow models to improve prediction and support dam safety assessments.
Keywords
geostatistics
kriging
sequential Gaussian simulation
groundwater level
Tangab Dam
Subjects
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