The model was developed as a tool to better understand the complex and interdependent stream-aquifer system, and to provide guidance for the management of regional water resources. Water management topics relevant to the Santa Cruz AMA include bi-national water issues and the reliability of water supplies. This model was primarily calibrated over the recent effluent-dominated groundwater flow regime (1997-2002) because of the availability of high quality head, flow and pumping data. Thus, some model boundary conditions calibrated over recent periods may not necessarily be representative of pre-effluent conditions.