Evaluating least absolute deviation regression as an inverse model in groundwater flow calibration

The automated inverse procedure built into the US Geological Survey MODFLOW groundwater model works well with single layer geologic systems; however, it does not work well with multi-layer systems. This dissertation provides the Least sum Absolute Deviation regression and Expectation Maximization procedures. These new FORTRAN procedures were added to the parameter estimation source code of the MODFLOW groundwater computer model. The resulting inverse MODFLOW model can now calculate the hydraulic conductivity for multi-layer systems. The model was applied to Walnut Creek watershed in Iowa. Hydraulic conductivity parameters computed with the inverse watershed model using the Least sum Absolute Deviation regression and the Expectation Maximization procedures agree with published data. A forward groundwater model of the larger encompassing Upper Skunk River basin in Iowa was created. The hydraulic conductivity parameters computed by both Walnut Creek inverse models were used to create two forward basin models. Using the hydraulic conductivity from the Least sum Absolute Deviation regression and Expectation Maximization methods on the Upper Skunk River basin produced model heads for Walnut Creek that were within two meters of observed heads. The MODFLOW model predicted a confined aquifer system while the Least sum Absolute Deviation regression and Expectation Maximization model predicted an unconfined system. Literature documents Walnut Creek as an unconfined system. This modified MODFLOW model is a better tool for modeling multi-layer groundwater aquifers.

Name thesis:degree_name

Doctor of Philosophy (Ph.D.)

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Geosciences

Grantor dc:publisher

Colorado State University. Libraries

Year dc:date.issued

2004

Authors dc:creator

• Huddleston, John Matthew, author
• Smith, Freeman M., advisor

• geophysics
• statistics

Statement dc:rights

• Copyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.

Language dc:language.iso

eng, English

Identifier URI

https://doi.org/10.25675/3.026013

OAI identifier oai:identifier

oai:mountainscholar.org:10217/243159