Evaluation of automated groundwater level measurements for transmissivity and storativity calculation

Abstract

In this paper, we discuss the accuracy of aquifer transmissivity (T) and storativity (S) values, obtained through the processing of hourly and 5-min groundwater level data, regularly and accurately recorded by automated stations. In particular, we discuss the role of the selection of (a) the initial undisturbed hydraulic head level, which might be influenced by prior pumping cycles, and (b) the exact time of start or shutdown of the pump, which might not be exactly recorded. Furthermore, the accuracy of T and S values based on sparse measurements is also examined. The Cooper–Jacob method and the recovery test method have been applied to obtain both T and S, and T values, respectively. Groundwater level measurements at Moudania aquifer, Chalkidiki, Greece, are used as an illustrative example. Our main conclusions are (a) assuming that pumping starts earlier than it actually does, leads to the underestimation of T and the overestimation of S, (b) transmissivity might be overestimated if the residual drawdown, due to previous pumping cycles, is substantial, (c) in recovery tests, the deviation of the straight line that fits the experimental points from the point (1,0) is an indication of residual drawdown, and (d) sparse measurements can offer reasonable estimates.

Groundwater vulnerability assessment using a GIS-based DRASTIC method in the Erbil Dumpsite area (Kani Qirzhala), Central Erbil Basin, North Iraq

“…Hydraulic conductivity Hydraulic conductivity characterizes the velocity of groundwater flow into the saturated zone and depends on the aquifer materials. Pumping tests are commonly employed to evaluate this hydrogeological parameter (Kirlas, 2021). Higher hydraulic conductivity values increase the potential for groundwater pollution (Victorine Neh et al 2015).…”

A GIS-Based Comparative Groundwater Vulnerability Assessment Using Modified-DRASTIC, Modified-SINTACS and NV Index in a Porous Aquifer, Greece

“…Water demand for irrigation and domestic purposesis high, especially during the period spanning from May to September. Moreover, the combination of surface water scarcity and generally inadequate yearly rainfall renders groundwater the only viable source of water [57]. However, this fact has caused a noteworthy decrease in the groundwater level throughout the area.…”

“…Higher hydraulic conductivity values portend higher groundwater pollution potential [79]. In previous research, the Cooper-Jacob and the recovery test methods were employed to groundwater level data in order to estimate the hydrogeological parameters of the studied aquifer, namely hydraulic conductivity, transmissivity and storativity [55,57,80,81]. Results showed that the hydraulic conductivity ranged from about 1 × 10 −6 m/s to 2 × 10 −5 m/s, and its values were considered slightly low [55,57,80,81].…”

Quantification of groundwater storage heterogeneity in weathered/fractured basement rock aquifers using electrical resistivity tomography: Sensitivity and uncertainty associated with petrophysical modelling

“…This would suggest either that the porosity derived from this model in this upper part of the bedrock is reflective of the aquifer's effective storage capacity rather than the total porosity (including bound and unconnected groundwater), or that storativity and total porosity are not significantly different in these horizons. However, it is also likely that storativity values obtained from hydraulic testing are providing an overestimation of the actual aquifer storativity due to being representative of a small area abound the boreholes (because of the low pumping rates applicable for hydraulic testing such low productivity hydrogeological environment) affected by locally increased porosity associated to the downhole hammer drilling technique (Kirlas and Katsifarakis, 2020;Pongmanda and Suprapti, 2020). Such artificially increased porosity and storativity would have relatively more effect on deeper (more massive) than shallower bedrock horizons.…”