Recently, River Information Systems that integrate a variety of riverine information have been widely developed, driven by information technologies. The present study attempts to develop a software called HydroConnector that dynamically integrates river-based numerical modeling or post-processing with in situ data, based upon a data searching technique that uses a hydro web service built on top of an ODM-based database, following a CUAHSI standard. It fundamentally differs from the conventional direct access to the database for acquiring a given period of a dataset. Such a hydro web service and ODM-based database were built by utilizing existing real-time stream gaging data, and they are dynamically connected with an HPG model that estimates the stage height for an ungaged site. As a result, the newly developed HydroConnector is very intuitive for the user, due to the user-friendly GUI; it facilitates modeling processes by automatically connecting remotely located data and a specific numerical model, without further laborious data pre- and post-processing. In fact, the HPG model consists of a pre-established diagram based on simulated outputs from one-dimensional river models, such as HEC-RAS, operated for the possible flow conditions, and it is able to estimate the stage height for an ungaged site, driven by the given downstream stage height and upstream flow discharge. The HydroConnector incorporates both the web service and the HPG model, which enables the making of dynamic data pre-processing adjusted for the numerical model, and automatically operates the HPG model, to finally provide the targeted ungaged stage height. Acknowledgement This research was supported by a grant (11-TI-C06) from the Advanced Water Management Research Program, funded by the Ministry of Land, Infrastructure and Transport of the Korean government.