Dataset storing natural daily streamflow and monthly water balance components simulated with SWAT for the Vistula and Odra basins, for the time period 1954-2013, developed within the CHASE-PL project CPL-NH dataset stores SWAT (Soil and Water Assessment Tool) simulation output for the Vistula and Odra basins, at sub-basin level (water balance components) and at reach level (natural streamflow). The following nine water balance components (expressed in mm, as the amount of water per unit sub-basin area) are included: precipitation, snow melt, potential evapotranspiration, actual evapotranspiration, soil water content, percolation, surface runoff, baseflow, and water yield. Simulated streamflow is natural due to the fact that water management was not included in the model setup. The model was ran using the accompanying CPLFD-GDPT5 dataset (DOI: 10.4121/uuid:e939aec0-bdd1-440f-bd1e-c49ff10d0a07) as the climate input. Model calibration for the time period 1991-2000 was performed using a novel spatial approach oriented on eight flow regime clusters containing in