Sustainable decisions in water resources management require scientifically sound information on water availability, which includes the quantification of the spatial and temporal changes of water balance variables.

Central support in hydrological decision making arises from hydrological modelling which, in turn, depends on meteorological input. In poorly gauged basins, this task is hampered by the fact that only little hydro-
meteorological information is available.

Station data are only available with a considerable temporal delay and therefore unsuitable for specific questions in water resources management, in particular where basin wide and near real time monitoring is required to support stakeholders and water management authorities in operational irrigation, water supply, or running hydro-power strategies.

Therefore, other data sources for the meteorological driving information for hydrological simulations have to be used.

For near real time estimations on current water resources and fluxes a model based water balance monitoring system, based on a joint atmospheric-hydrological model system, is applied.
For the meteorological simulations, the mesoscale meteorological model MM5 is used.

Results of the meteorological simulations are applied as meteorological input data for hydrological simulations, which are performed using the Water Balance Simulation Model WaSiM.

The results of the joint atmospheric-hydrological simulations, which are depicted in Figure 1-3, in expost hindcasting mode for the year 2004 show that the meteorological model MM5 is able to provide the required meteorological input data for near real time hydrological simulations in reasonable quality.