Contemporary open source JAVA technologies implemented within the EURANOS project for the
cross-platform re-engineering of the decision support system RODOS (JRODOS) were used also
to redesign the Hydrological Dispersion Module (HDM) of this system. JHDM – the
hydrological model chain of JRODOS contains models to simulate the radionuclide transport
in the system “atmospheric fallout on watershed – river net” and calculate the doses via
aquatic pathways. JHDM used for this purpose a limited number of the input parameters to
characterize the hydrological properties of the catchment/river network of interest. The
pilot implementation of JHDM for the Vistula river basin carried out by POLATOM and
supported by the national hydrological institute, demonstrated good perspectives of the
approach used in JHDM for the decision support in cases of accidental contamination of
water systems. Particular needs for further improvements of the JHDM software system have
been identified.