The Hydrologic Information System Project of the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) has successfully created a large-scale prototype Hydrologic Information System (HIS). This system catalogs and provides access to over 23 million time series of hydrologic data, which are distributed across the United States at various academic, research, and governmental data providers. The service-oriented architecture that enables the HIS comprises distributed hydrologic data servers, a centralized series catalog, and various client software applications, and is supported by WaterML, a standardized language for transmission of hydrologic data. The current architectural model, termed the Network-Observations Model, of the HIS relies on a searchable central catalog of series metadata. Harvesting series metadata from large federal data providers, such as the USGS, EPA, and NCDC, has proven a laborious undertaking and involves custom database migration tools. This time-consuming harvesting task, coupled with a multitude of custom-coded solutions at the central series catalog has led to concerns with the long-term sustainability of the current architectural model. A new architectural model, termed the Services Stack Model, is proposed in this thesis. In the proposed model, a catalog of services metadata, rather than of series metadata is used to connect hydrologic data consumers with data providers. Internationally-recognized web service and data encoding standards, including the upcoming WaterML2.0 specification, from the Open Geospatial Consortium are used as the backbone of the new model. The proposed model will hopefully lead to greater acceptance of the CUAHSI-HIS, and result in increased sustainability and reduced maintenance of the system in the long-term. / text