Certification Tests of MODFLOW Implementation in the Integrated Hydrologic Model

Abstract

MODFLOW is a three-dimensional finite-difference groundwater flow model. IHM (integrated hydrologic model) is a recent integrated model developed to simulate the interaction between surface water and groundwater, which formally couples HSPF and MODFLOW. The purpose of this research was to define a set of comparisons between IHM-MODFLOW96 (IHM-MF96) and standard MODFLOW96 (MF96) to certify that IHM-MF96 is acceptable to use with the IHM. The certification tests were necessary to determine whether model runs with modifications to the source code of MF-96, contained in the source code of IHM-MF96, would alter the head or flux results when compared to model runs with the standard source code. The tests were conducted over a range of problem sets, which are anticipated to cover the range of hydrogeologic conditions and anticipated applications for which IHM will be used in westcentral Florida. The tests results showed the MF96 implementation in IHM appears to produce virtually the same results as the standard MF96. None of the changes to MF96 as implemented in IHM had a material effect on any of the tested conditions. Based on the test results, the IHM MODFLOW package was expected to produce the same results, as would the standard MF96.