DIFFICULTIES IN MODELING SYSTEMS WITH EXTREME CLIMATE RECORDS: IS A MODEL OF A GROUNDWATER SYSTEM DURING A DROUGHT UNREPRESENTATIVE OR CONSERVATIVE?

The hydrology of an alluvial groundwater system can be heavily dependent on the temporal climatology of a region. In particular, agricultural basins that have been impacted by regional drought conditions, evolving irrigation techniques, and water use reappropriations can require a recalibration of groundwater models-both conceptually and quantitatively-before future predictions can be attempted. Determining the appropriate conditions for such recalibrations can result in complications with a models ability to both represent a fixed past and predict an changing future. Utilizing a historically agricultural region in Colorado, USA as a case study, an investigation was undertaken as to how different groundwater modeling techniques can affect the operations of future use change and its impacts on regional water users. Utilizing a steady-state MODFLOW model, an averaged transient MODFLOW model, and a climatically variable transient MODFLOW model, an attempt was made to determine if modeling a system in flux should be considered merely conservative or unrepresentative for the purposes of future demands and impacts.