Impact of spatial data resolution on model results

Introduction Conclusions References Tables Figures Back Close Papers published in Hydrology and Earth System Sciences Discussions are under open-access review for the journal Hydrology and Earth System Sciences Abstract Introduction Conclusions References Tables Figures Back Close Abstract This paper analyses the effect of spatial input data resolution on the simulated water balances and flow components using the multi-scale hydrological model TOPLATS. A data set of 25m resolution of the central German Dill catchment (693 km 2) is used for investigation. After an aggregation of digital elevation model, soil map and land 5 use classification to 50 m, 75 m, 100 m, 150 m, 200 m, 300 m, 500 m, 1000 m and 2000 m, water balances and water flow components are calculated for the entire Dill catchment as well as for 3 subcatchments without any recalibration. The study shows that both model performance measures as well as simulated water balances almost remain constant for most of the aggregation steps for all investigated catchments. Slight 10 differences occur for single catchments at the resolution of 50–500 m (e.g. 0–3% for annual stream flow), significant differences at the resolution of 1000 m and 2000 m (e.g. 2–12% for annual stream flow). These differences can be explained by the fact that the statistics of certain input data (land use data in particular as well as soil physical characteristics) changes significantly at these spatial resolutions, too. The impact 15 of smoothing the relief by aggregation occurs continuously but is not reflected by the simulation results. To study the effect of aggregation of land use data in detail, three different land use scenarios are aggregated which were generated aiming on economic optimisation at different field sizes (0.5 ha, 1.5 ha and 5.0 ha). The changes induced by aggregation of these land use scenarios are comparable with respect to catchment 20 water balances compared to the current land use. A correlation analysis only in some cases reveals high correlation between changes in both input data and in simulation results for all catchments and land use scenarios combinations (e.g. evapotranspiration is correlated to land use, runoff generation is correlated to soil properties). Predominantly the correlation between catchment properties (e.g. topographic index, transmis-25 sivity, land use) and simulated water flows varies from catchment to catchment. This study indicates that an aggregation of input data for the calculation of regional water balances using TOPLATS type models leads to significant …