Saturated-unsaturated flow to a well with storage in a compressible unconfined aquifer Phoolendra Kumar Mishra 1,2 and Shlomo P. Neuman 1 Received 27 October 2010 ; revised 3 January 2011 ; accepted 3 February 2011 ; published 28 May 2011. [1] Mishra and Neuman (2010) developed an analytical solution for flow to a partially penetrating well of zero radius in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from responses recorded in the saturated and/ or unsaturated zones. Their solution accounts for horizontal as well as vertical flows in each zone. It represents unsaturated zone constitutive properties in a manner that is at once mathematically tractable and sufficiently flexible to provide much improved fits to standard constitutive models. In this paper we extend the solution of Mishra and Neuman [2010] to the case of a finite diameter pumping well with storage; investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten [1980]–Mualem [1976] model; use our solution to analyze 11 transducer-measured drawdown records from a seven-day pumping test conducted by University of Waterloo researchers at the Canadian Forces Base Borden in Ontario, Canada; validate our parameter estimates against manually-measured drawdown records in 14 other piezometers at Borden; and compare (a) our estimates of aquifer parameters with those obtained on the basis of all these records by Moench [2008], (b) on the basis of 11 transducer-measured drawdown records by Endres et al. [2007], (c) our estimates of van Genuchten–Mualem parameters with those obtained on the basis of laboratory drainage data from the site by Akindunni and Gillham [1992], and (d) our corresponding prediction of how effective saturation varies with elevation above the initial water table under static conditions with a profile based on water contents measured in a neutron access tube at a radial distance of about 5 m from the center of the pumping well. We also use our solution to analyze 11 transducer-measured drawdown records from a 7 day pumping test conducted by University of Waterloo researchers at the Canadian Forces Base Borden in Ontario, Canada. We validate our parameter estimates against manually measured drawdown records in 14 other piezometers at Borden. We compare our estimates of aquifer parameters with those obtained on the basis of all these records by Moench (2008) and on the basis of 11 transducer- measured drawdown records by Endres et al. (2007), and we compare our estimates of van Genuchten–Mualem parameters with those obtained on the basis of laboratory drainage data from the site by Akindunni and Gillham (1992); finally, we compare our corresponding prediction of how effective saturation varies with elevation above the initial water table under static conditions with a profile based on water contents measured in a neutron access tube at a radial distance of about 5 m from the center of the pumping well. Citation: Mishra, P. K., and S. P. Neuman (2011), Saturated-unsaturated flow to a well with storage in a compressible unconfined aquifer, Water Resour. Res., 47, W05553, doi:10.1029/2010WR010177. 1. Introduction [2] Drawdowns generated by extracting water from a large-diameter (e.g., water supply) well in an unconfined aquifer are affected by wellbore storage. Narasimhan and Zhu [1993] used a numerical model to demonstrate that early time drawdown in an unconfined aquifer tends to be masked by wellbore storage effects. The same was con- firmed analytically [Moench, 1997] and numerically [Moench, 2008] in the context of a 7 day pumping test con- ducted by University of Waterloo researchers at the Cana- dian Forces Base Borden in Ontario, Canada. Yet virtually all analytical solutions of flow to a well in an unconfined aquifer, other than that of Moench [1997], have considered the pumping well to have zero radius and, therefore, no 1 Department of Hydrology and Water Resources, University of Arizona, Tucson, Arizona, USA. 2 Now at Hydrology, Geochemistry and Geology Group, Los Alamos National Laboratory, Los Alamos, New Mexico, USA. Copyright 2011 by the American Geophysical Union. 0043-1397/11/2010WR010177 W05553 1 of 15 WATER RESOURCES RESEARCH, VOL. 47, W05553, doi :10.1029/2010WR010177, 2011