Numerical Analysis of the Effect of Subgrid Variability in a Physically Based Hydrological Model on Runoff, Soil Moisture, and Slope Stability

In coarse resolution hydrological modeling, we face the problem of subgrid variability, effects which are difficult to express and often hidden in parameterization calibration. We present a numerical experiment with physically based model ParFlow-CLM quantify effect heterogeneities headwater catchments within cell size typically used for regional applications. simulate homogeneous domains topography or soil thickness two climates types. The presence side slope is main error source, leading large underestimation runoff, marginally also evapotranspiration. spatial distribution saturation variability leads landslide risk. Soil second influential property, affecting moisture surface runoff formation. Results consistent types considered. topographic wetness index approach tested as way downscale simulations domain. Although this method successful reproducing some patterns, it fails when grid mean inaccurate does not represent subsurface flow paths accurately. conclude that ignoring coarse-scale models may lead locally instability. Users such should be aware these biases consider ways include predictions.