ANALYSIS AND MODELING OF NON-DARCIAN FLOW IN GROUNDWATER WITH MODFLOW CFP

Author

Roshan Adhikari, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2014

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Bravo, Rolando

Abstract

Conventional methods of groundwater modeling are based on applying laminar flow condition in the aquifer and assuming primary porosity to be present in the aquifer. But in cases where conduits, caves, springs and sinks characterize the aquifer as in karst, this assumption is inappropriate. In addition to Darcian flow condition in matrix portion of aquifer there should be consideration for dealing with non-Darcian flow in the conduits where high velocity of flow occurs. Presence of conduit network in the aquifer greatly affects the potentiometric heads within the aquifer. Hence the necessity of different modeling method has long been realized for karst aquifers. MODFLOW-Conduit Flow Process (CFP) has the capability to simulate both turbulent and laminar groundwater flow condition present in caves and conduits portion of karst aquifers. This study examined the cases where a sub-regional model was used to simulate discharge of springs and heads both with and without considering the presence of conduit network in the aquifer using MODFLOW-CFP 2005 and MODFLOW 2005 respectively. Comparison of results showed that the potentiometric head in the area consisting conduit network were unrealistically low when conduit network was not considered to be present in the matrix. This study also introduces and uses a program called CONGEN to generate conduit flow process file for CFP Mode 1. Furthermore this study also carried out the benchmark testing to examine the capability of MODFLOW-CFP to simulate both laminar and turbulent pipe flow in the conduits for a sub-regional scale. Results from transient state simulation indicate that, although MODFLOW-CFP considers both laminar and turbulent flow conditions in the pipe like conduits in the karst, it underestimated the peak discharge of the springs in this study.