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Geofluids
Volume 2018, Article ID 3765743, 30 pages
https://doi.org/10.1155/2018/3765743
Research Article

Simulating the Evolution of Fluid Underpressures in the Great Plains, by Incorporation of Tectonic Uplift and Tilting, with a Groundwater Flow Model

1Earth Systems Modeling Branch, Integrated Modeling and Prediction Division, Water Mission Area, US Geological Survey (USGS), Denver Federal Center, P.O. Box 25046, MS 406, Lakewood, CO 80225, USA
2Central Energy Resources Science Center, US Geological Survey (USGS), Denver Federal Center, P.O. Box 25046, MS 964, Lakewood, CO 80225, USA
3Central Energy Resources Science Center, US Geological Survey (USGS), Denver Federal Center, P.O. Box 25046, MS 980, Lakewood, CO 80225, USA
4Earth Systems Processes Division, Water Mission Area, US Geological Survey (USGS), Denver Federal Center, P.O. Box 25046, MS 406, Lakewood, CO 80225, USA

Correspondence should be addressed to Amjad M. J. Umari; vog.sgsu@iramujm

Received 13 May 2017; Revised 18 August 2017; Accepted 1 October 2017; Published 26 February 2018

Academic Editor: John A. Mavrogenes

Copyright © 2018 Amjad M. J. Umari et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Underpressures (subhydrostatic heads) in the Paleozoic units underlying the Great Plains of North America are a consequence of Cenozoic uplift of the area. Based on tectonostratigraphic data, we have developed a cumulative uplift history with superimposed periods of deposition and erosion for the Great Plains for the period from 40 Ma to the present. Uplift, deposition, and erosion on an 800 km geologic cross-section extending from northeast Colorado to eastern Kansas is represented in nine time-stepped geohydrologic models. Sequential solution of the two-dimensional diffusion equation reveals the evolution of hydraulic head and underpressure in a changing structural environment after 40 Ma, culminating in an approximate match with the measured present-day values. The modeled and measured hydraulic head values indicate that underpressures increase to the west. The 2 to 0 Ma model indicates that the present-day hydraulic head values of the Paleozoic units have not reached steady state. This result is significant because it indicates that present-day hydraulic heads are not at equilibrium, and underpressures will increase in the future. The pattern uncovered by the series of nine MODFLOW models is of increased underpressures with time. Overall, the models indicate that tectonic uplift explains the development of underpressures in the Great Plains.