Modeling groundwater-surface water interactions in an operational setting by linking RiverWare with MODFLOW

Accurate representation of groundwater-surface water interactions is critical to modeling low river flow periods in riparian environments in the semi-arid southwestern United States. This thesis presents a modeling tool with significant potential for improved operational decision-making in river reaches influenced by surface-groundwater interactions.; A link between RiverWare and MODFLOW was developed. An interactive time stepping approach is used to link the two models, in which both models run in parallel exchanging data after each time-step. This linked framework incorporates several features critical to modeling groundwater-surface interactions in riparian zones, including riparian evapotranspiration, localized variations in seepage rates, irrigation return flows and rule-based water allocations to users and/or environmental flows. Several applications of the linked RiverWare-MODFLOW model along the Rio Grande near Albuquerque, New Mexico are presented. In this region, over-appropriation of human water use has adversely impacted the habitat of the endangered Rio Grande silvery minnow.