Approximate Solutions for Radial Travel Time and Capture Zone in Unconfined Aquifers

Abstract

Radial time-of-travel (TOT) capture zones have been evaluated for unconfined aquifers with and without recharge. The solutions of travel time for unconfined aquifers are rather complex and have been replaced with much simpler approximate solutions without significant loss of accuracy in most practical cases. The current "volumetric method" for calculating the radius of a TOT capture zone assumes no recharge and a constant aquifer thickness. It was found that for unconfined aquifers without recharge, the volumetric method leads to a smaller and less protective wellhead protection zone when ignoring drawdowns. However, if the saturated thickness near the well is used in the volumetric method a larger more protective TOT capture zone is obtained. The same is true when the volumetric method is used in the presence of recharge. However, for that case it leads to unreasonableness over the prediction of a TOT capture zone of 5 years or more.

Capture Zone of a Multi-Well System in Bounded Rectangular-Shaped Aquifers: Modeling and Application

“…The study of well(s) capture zone is very useful for the design of contaminated groundwater remediation projects, such as pump-and-treat, plume containment, bioremediation and chemical oxidation, surface-subsurface water interactions, well-head protection plan, and etc. Following the early work of Muskat (1946), many studies have been conducted on the delineation of well-capture zone (Bear 1972;Javandel et al 1984;Javandel and Tsang 1986;Kinzelbach et al 1992;Grubb 1993;Yang et al 1995;Faybishenko et al 1995;Bakker and Strack 1996;Schafer 1996;Bair and Lahm 1996;Shan 1999;Zhan 1999a, b;Eradmann 2000;Christ and Goltz 1999, 2002Luo and Kitanidis 2004;Cunningham et al 2004;Kompani-Zare et al 2005;Fienen et al 2005;Zhou and Haitjema 2012;Ataie-Ashtiani et al 2012;De Smedt 2014), in most of which the theory of complex velocity potential is used for describing the capture zone of well(s) in extensive aquifers.…”

Analytical solution for the catchment zone of a well located near a groundwater divide in a recharged semi-confined aquifer

“…Although in none of these studies groundwater recharge is taken into account, these results are often used in practice for delineating well-catchment zones in recharged aquifers. At present, there are only a few analytical solutions for delineating well catchment zones in recharged aquifers, i.e., Chapuis (2011) and Zhou and Haitjema (2012) for pure radial flow to a pumping well and De Smedt (2014) for a pumping or injection well located exactly on a groundwater divide.…”

A Python Script to Compute Isochrones for MODFLOW

“…Deterministic captures areas are generated using analytical solutions (Bear and Jacobs 1965;Javandel and Tsang 1986;Ceric and Haitjema 2005), semi-analytic methods (Pollock 1988;Blandford and Huyakorn 1991;Fienen et al 2005;Raymond et al 2006;Zhou and Haitjema 2012), stochastic approaches (Franzetti and Guadagnini 1996;Guadagnini and Franzetti 1999) or numerical methods (Pollock 1989;Orzol 1997;Broers and van Geer 2005;Rayne et al 2014). Deterministic captures areas are generated using analytical solutions (Bear and Jacobs 1965;Javandel and Tsang 1986;Ceric and Haitjema 2005), semi-analytic methods (Pollock 1988;Blandford and Huyakorn 1991;Fienen et al 2005;Raymond et al 2006;Zhou and Haitjema 2012), stochastic approaches (Franzetti and Guadagnini 1996;Guadagnini and Franzetti 1999) or numerical methods (Pollock 1989;Orzol 1997;Broers and van Geer 2005;Rayne et al 2014).…”

“…A large amount of models for the delineation of such boundaries of time-related capture zones (isochrones) in groundwater flow have been developed so far. Deterministic captures areas are generated using analytical solutions (Bear and Jacobs 1965;Javandel and Tsang 1986;Ceric and Haitjema 2005), semi-analytic methods (Pollock 1988;Blandford and Huyakorn 1991;Fienen et al 2005;Raymond et al 2006;Zhou and Haitjema 2012), stochastic approaches (Franzetti and Guadagnini 1996;Guadagnini and Franzetti 1999) or numerical methods (Pollock 1989;Orzol 1997;Broers and van Geer 2005;Rayne et al 2014). While analytical solutions can be applied only to a few cases where some simplifications have to be imposed, numerical methods are feasible to take into account complex scenarios as for example, heterogeneous porous media, presence of multiple wells, specific boundary conditions (for instance the presence of rivers, barrier, etc.).…”