The amount and intensity of precipitation and proportions which infiltrate, percolate, run on the surface downslope and evaporate fluctuate in the watershed through the year – according to rainy and dry seasons or winter and summer seasons in the respective watershed.

From watershed to watershed the amount, intensity and frequency of precipitation and the rates of the individual processes of the hydrological cycle also vary. This depends on the specific characteristics of the individual watersheds (see figures).

If, for instance, the soil is relatively impermeable due to compaction, less water can infiltrate into the soil. A greater amount of precipitation will under these conditions run downward as overland flow. Thus, also the water balances of different watersheds vary [3; 5].