Geostatistics as a groundwater exploration planning tool: case of a brackish-saline aquifer
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ORIGINAL PAPER
Geostatistics as a groundwater exploration planning tool: case of a brackish-saline aquifer Mohammad H. Makkawi
Received: 10 December 2013 / Accepted: 31 March 2014 # Saudi Society for Geosciences 2014
Abstract This paper discusses a geostatistical approach to model a groundwater aquifer in 3-D. The study aims at utilizing geostatistics as a tool for characterizing zones of betterwater quality in a brackish-saline aquifer. In particular, the geostatistical model was constructed to characterize the aquifer’s salinity, represented by total dissolved solids (TDS), using logs of porosity and resistivity. Quality-checked estimated TDS vertical profiles were employed to construct and model horizontal and vertical semivariograms. Parameters of semivariogram models were used to develop both the kriging plan and the generated model. Results of this modeling process are shown in the form of horizontal salinity distribution maps. The aquifer was sliced into 20 layers, each 20 m thick, to represent its overall thickness. Salinity layers maps reflect vertical stratification of TDS concentrations in the aquifer and show that water quality deteriorates with depth and toward the northern part of the aquifer. Relatively better-quality water (TDS ≤10,000 mg/l) can be found at depths between 100 and 250 m below the aquifer’s top in both eastern and southeastern parts. Water in the same interval to the western and southwestern parts reflects the presence of higher TDS concentration. From a planning point of view, it is more feasible to target the eastern part of the aquifer for pumping and desalination purposes. In addition, the generated model could be utilized as an initial condition for flow simulation.
Keywords Geostatistics . Kriging . Groundwater salinity . Water resources exploration
M. H. Makkawi (*) Earth Sciences Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia e-mail: [email protected]
Introduction Aquifer characterization techniques like geostatistical methods are practical planning tools to describe the spatial distribution of hydrogeologic parameters. This, in particular, is very important when planning to identify relatively fresh water zones and recommend drilling locations in brackishsaline aquifers. These aquifers might be the only sources of groundwater in arid regions. The power of geostatistics comes from its ability to integrate and utilize various and limited data sets to model the subsurface complex environments by either interpolation or simulation. Example of an important water quality parameter that concerns water-planners in arid regions is the total dissolved solids (TDS), which reflects an aquifer’s natural quality to supply drinking, household, industrial, and agricultural water. It is vital to target good-quality groundwater zones to satisfy the end users and reduce treatment costs. At normal circumstances and in areas close to seashores, treating highTDS groundwater could be infeasible compared to sea desalination approach. In the case of h
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