Improved forward and inverse analyses of saturated-unsaturated flow toward a well in a compressible unconfined aquifer

• Published in: Water resources research Vol. 46; no. 7
• Main Authors: Mishra, Phoolendra Kumar, Neuman, Shlomo P.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-07-2010; John Wiley & Sons, Inc
• Subjects: Aeration zone; anisotropy; Aquifers; Conductivity; Drawdown; Geological surveys; Groundwater; Hydraulic gradient; Hydraulic properties; Hydraulics; Hydrology; Laplace transforms; Marine; partial penetration; pumping test; Saturated flow; Scientific apparatus & instruments; unconfined aquifer; Unconfined aquifers; Unsaturated flow; unsaturated properties; USA, Massachusetts, Cape Cod
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1029/2009WR008899

We present an analytical solution for flow to a partially penetrating well in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from drawdowns recorded in the saturated and/or unsaturated zone. We improve upon a previous such solution due to Tartakovsky and Neuman (2007) by (1) adopting a more flexible representation of unsaturated zone constitutive properties and (2) allowing the unsaturated zone to have finite thickness. Both solutions account for horizontal as well as vertical flows throughout the system. We investigate the effects of unsaturated zone constitutive parameters and thickness on drawdowns in the saturated and unsaturated zones as functions of position and time; demonstrate the development of significant horizontal hydraulic gradients in the unsaturated zone in response to pumping; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten‐Mualem constitutive model; use our solution to analyze drawdown data from a pumping test conducted by the U.S. Geological Survey at Cape Cod, Massachusetts; and compare our estimates of van Genuchten‐Mualem parameters with laboratory values obtained for similar materials in the area.