The present data set demonstrates the potential of combining observed river discharge information with a climate-driven Water Balance Model in order to develop composite runoff fields which are consistent with observed discharges. Such combined runoff fields preserve the accuracy of the discharge measurements as well as the spatial and temporal distribution of simulated runoff, thereby providing the "best estimate" of terrestrial runoff over large domains.

The method applied in the preparation of this data set utilizes a gridded river network at 30-minute spatial resolution to represent the riverine flow pathways and to link the continental land mass to oceans through river channels. Selected gauging stations from the Global Runoff Data Centre data archive were co-registered to a simulated topological network (STN-30p) developed at the University of New Hampshire. Inter-station regions between gauging stations along the STN-30p network were identified. Inter-station discharge and runoff were calculated to compare observed runoff with outputs from the water balance model (WBM) simulation. Correction coefficients based on the ratio of observed and simulated runoff for inter-station areas were calculated and applied against simulated runoff to create composite runoff fields.

The present CD contains not only "UNH-GRDC Composite Runoff Fields V1.0" but also intermediate data sets, such as station attributes and long-term monthly regimes of the selected gauging stations. Also included on the CD are the simulated topological network (STN-30p), STN-30p derived attributes for the selected stations and gridded fields of the inter-station regions along STN-30p.

An HTML based data explorer was developed to help users of the CD-ROM view the data. With a standard web browser and the CD it is possible to navigate from a global view of the data, down to a subbasin or station level.

The printed version of the report can be ordered free of charge from GRDC (grdc@bafg.de) or WMO (dhwr@gateway.wmo.ch).

Note: Due to inaccuracies in the topographical dataset used for the compilation of the simulated river network, errors may occur in the graphical display of certain lower-order rivers. Users are invited to send their comments and notification of errors to the e-mail addresses shown above.