This paper seeks to emphasize the flow variability in the Calnistea catchment by analyzing the local physiographic factors. The research has shown that the amount of precipitation that falls to the ground is low, the rocks in the region are soft, but highly permeable, gradients are gentle in most of the territory and vegetal cover is sparse and therefore cannot hold important amounts of water. Under the circumstances, the flow is controlled especially by precipitation, gradient and rock permeability, which largely explains the rather low values of the drainage density, as well as the frequency with which the rivers dry up completely. The moisture deficit of the summer season is compensated to a certain extent by the existence of a chain of ponds along the main streams. The situation could further be improved if local authorities will find the necessary financial means in order to excavate artificial channels to bring water from the neighboring catchments. Although the flow values are generally low, under exceptional synoptic conditions the heavy rainfalls can lead to the formation of flash floods that can damage settlements, transportation routes and crops. Consequently, it is necessary to build protection levees in the lowlands and to regulate the stream flow.