The Water Information System (WIS), developed by the Institute of Hydrology as a hydrology-oriented GIS, was used as the spatial and time variable input, user interface and graphic output of the results for the hydrological modelling. A physically-based, quasi-distribution hydrological model (TOPMODEL) was linked with WIS as one of its application modules. Special techniques within the WIS framework allowing on-line data manipulation (data retrieving and updating) were developed. In particular, the database design was modified to handle time-series grids and the user interface was upgraded. Monte-Carlo simulation within a generalized likelihood uncertainty estimation (GLUE) framework, performed on a transputer system and initialized from WIS, was used for the calibration of TOPMODEL. -Authors