Improved hydrological modeling for remote regions using a combination of observed and simulated precipitation data

Precipitation, as simulated by climate models, can be used as input in hydrological models, despite possible biases both in the total annual amount simulated as well as the seasonal variation. Here we elaborated on a new technique, which adjusted precipitation data generated by a high-resolution regional climate model (HIRHAM4) with a mean-field bias correction using observed precipitation. A hydrological model (USAFLOW) was applied to simulate runoff using observed precipitation and a combination of observed and simulated precipitation as input. The method was illustrated for the remote Usa basin, situated in the European part of Arctic Russia, close to the Ural Mountains. It was shown that runoff simulations agree better with observations when the combined precipitation data set was used than when only observed precipitation was used. This appeared to be because the HIRHAM4 model data compensated for the absence of observed data from mountainous areas where precipitation is orographically enhanced. In both cases, the runoff simulated by USAFLOW was superior to the runoff simulated within the HIRHAM4 model itself. This was attributed to the rather simplistic description of the water balance in the HIRHAM4 model compared to a more complete representation in USAFLOW.