Runoff response at different spatial scales: Moving from small experimental areas to mesoscale catchments

Small experimental catchments represent valuable tools for collection of detailed hydro-meteorological data and conceptualization of hydrological behaviour. Following an upscaling approach, they can also offer insights about the main rainfall-runoff processes occurring at larger scales. This paper aims at assessing whether the runoff generation mechanisms observed in small areas are representative of those occurring in larger basins. We compare the response of four nested catchments ranging from micro-scale to meso-scale in the Italian Dolomites analyzing 54 rainfall-runoff events. A similar threshold effect in the soil moisture-runoff relationship suggests the same processes operating at different scales and denotes the possibility of using hillslope-scale soil moisture measurements as indicators of the moisture conditions of larger areas. The event runoff coefficients are well described by the beta distribution, which reflects the decrease of stormflow with the increase of the watershed size. The catchment inter-variability of runoff coefficients are probably related to the watershed topographic properties, mostly in terms of extent of the buffering riparian zone.