 The software is used primarily by hydrogeologists to simulate groundwater flow and contaminant transport.The original version of Visual MODFLOW was first released in August 1994, and was developed for DOS by Nilson Guiguer, Thomas Franz and Bob Cleary.It was based on the USGS MODFLOW-88 and MODPATH codes, and resembled the FLOWPATH program that was also developed by Waterloo Hydrogeologic Inc.