If we sum up the data and observations derived from our researches on the Drava river, we conclude after consideration of surface water fauna and after comparison of chemical parameters that it influences the hyporheic water of a rough gravel-sandy alluvium more than 2 m deep, while in the compact sandy substratum it has less influence. The next conclusion is that the horizontal and vertical distribution of Proasellus slavus ssp.n. in the alluvium of the Drava river, depends upon the granulation of substratum, with reference so the largeness of interstices; that the populations vary in density and structure according to the nature of water which irrigates these alluviums; and finally upon the quantity of detritus which this water contains. Concerning the influence of the sewage waters the effect of a sudden action of very polluted water is not known but it is certain that the increasing of decaying material to the alfa-meso saprobial level of the river water does not threaten either the existence or the development of the populations of Proasellus slavus ssp.n.