ABSTRACTSpatial variations in runoff under different environmental conditions represent one of the key problems in hydrological as well as sedimentological and geomorphological studies. In this study the mesoscale runoff variability has been investigated with the help of campaign field measurements, made in many basins at the same time, which have complemented the routine hydrological observational activities. A thorough analysis of the physiography of the basin was performed before the field studies. This made it possible to choose the measurement sites objectively and to select the physiographic variables of importance for runoff variation and for the mathematical modelling of runoff. For the period with rain the spatial variability of runoff was best explained by the amount of precipitation, by‘relief’variables and by the percentage of forest, while for the period without precipitation the percentage of lakes proved to be the most important variable.The variability of runoff registered during the campaign field studies indicates the range of uncertainty, due to the application of only the permanent, macroscale hydrological network. This is especially significant when runoff information is required in ungauged basins for hydrological or geomorphological investigations.