Constant-head and variable-head injection tests for determining the hydraulic parameters of an aquitard
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PAPER
Constant-head and variable-head injection tests for determining the hydraulic parameters of an aquitard Yawen Xin 1
&
Zhifang Zhou 1 & Zhi Dou 1 & Mingwei Li 1 & Jun Ma 1
Received: 7 November 2019 / Accepted: 12 May 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Although specific storage (SS) is a crucial parameter for characterizing the dynamic water-release process in an aquitard, the Hvorslev analysis method is only capable of estimating the hydraulic conductivity (K), rather than SS. The Hvorslev method is based on an assumption of steady-state flow and uses the falling-head test. Considering the elastic water-release effect in an aquitard and the actual groundwater flow, two mathematical unsteady-state groundwater flow models (i.e., the constant-head and variable-head models), describing the head distribution are presented for a constant-head injection test (CHIT) and variable-head injection test (VHIT) performed in a multi-layered aquifer-aquitard system. The analytical solutions for the models are derived by Fourier transforms to estimate K and SS. The obtained K and SS values from the CHIT and VHIT were generally consistent, although the VHIT is recommended in practice. For the VHIT, estimating K using the Hvorslev analysis method under steadystate groundwater flow conditions resulted in a small relative error compared to the obtained result from the variable-head model. It was demonstrated that a certain relation existed between the constant-head and variable-head methods when the drawdown rate was lower than 1%, and so the constant-head method was applied to the VHIT data to determine K and SS. The synthetic error in the parameters was smaller than 10%, which indicated that the methods could be used interchangeably under these circumstances, thus simplifying the hydraulic parameter estimation process. Keywords Aquitard . Analytical solutions . Constant-head injection test . Variable-head injection test . Hydraulic parameters
Introduction Aquitards are an important part of a multi-layered aquiferaquitard system (Zhan and Bian 2006; Huang et al. 2014; Zhou et al. 2014), and such systems occur widely in alluvial plains and sedimentary basins (Konikow and Neuzil 2007). The hydraulic conductivity (K) and specific storage (SS) of an aquitard are crucial parameters for many environmental and groundwater resource problems. A variety of field tests have been used to estimate the aquitard K, including slug test (Bouwer and Rice 1976; Kipp and Land 1985; Landon et al. 2001; Audouin and Bodin 2007; Zhou et al. 2008), falling-
* Zhifang Zhou [email protected] Yawen Xin [email protected] 1
School of Earth Science and Engineering, Hohai University, Nanjing 210098, People’s Republic of China
head permeability test (Chen 2000; Landon et al. 2001; Genereux et al. 2008; Zhu 2009; Li et al. 2010; Lu et al. 2012; Huang et al. 2014; Burnette et al. 2016), double-ring infiltration test (Bodhinayake et al. 2004), and constant-head injection test (CHIT; Tavena and Leroue 1990; Cardenas
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