Abstract
Abstract. Increasingly, ground-based and airborne geophysical data sets are used to inform groundwater models. Recent research focuses on establishing coupling relationships between geophysical and groundwater parameters. To fully exploit such information, this paper presents and compares different hydrogeophysical inversion approaches to inform a field-scale groundwater model with time domain electromagnetic (TDEM) and electrical resistivity tomography (ERT) data. In a sequential hydrogeophysical inversion (SHI) a groundwater model is calibrated with geophysical data by coupling groundwater model parameters with the inverted geophysical models. We subsequently compare the SHI with a joint hydrogeophysical inversion (JHI). In the JHI, a geophysical model is simultaneously inverted with a groundwater model by coupling the groundwater and geophysical parameters to explicitly account for an established petrophysical relationship and its accuracy. Simulations for a synthetic groundwater model and TDEM data showed improved estimates for groundwater model parameters that were coupled to relatively well-resolved geophysical parameters when employing a high-quality petrophysical relationship. Compared to a SHI these improvements were insignificant and geophysical parameter estimates became slightly worse. When employing a low-quality petrophysical relationship, groundwater model parameters improved less for both the SHI and JHI, where the SHI performed relatively better. When comparing a SHI and JHI for a real-world groundwater model and ERT data, differences in parameter estimates were small. For both cases investigated in this paper, the SHI seems favorable, taking into account parameter error, data fit and the complexity of implementing a JHI in combination with its larger computational burden.
Highlights
Over the last decade, interest in geophysical methods for hydrogeological site characterization has been increasing (Vereecken et al, 2004; Hubbard and Rubin, 2000)
First a joint hydrogeophysical inversion (JHI) is conducted for the groundwater and the geophysical model
Parameter estimates remain similar to the separate inversion, which is likely caused by the large standard deviations associated with the geophysical parameters that are coupled with the groundwater model
Summary
Interest in geophysical methods for hydrogeological site characterization has been increasing (Vereecken et al, 2004; Hubbard and Rubin, 2000). This is due to the ability of geophysical methods to provide models of subsurface properties with a high spatial resolution, which are difficult to obtain from sparse borehole information. Significant resources are spent on the collection of regional geophysical data sets. Smaller-scale surveys have been conducted using a variety of geophysical techniques such as ERT (electrical resistivity tomography, Kemna et al, 2002), induced polarization (Slater, 2007) and magnetic resonance sounding (Legchenko and Valla, 2002)
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