Seston is defined as all matter suspended in the water column, although the term is more commonly used in the context of suspended organic matter. Seston concentrations are the result of complex relations of intake and processing of allochthonous and autochthonous, organic and inorganic matter, their sedimentation and resuspension, and the discharge and flow velocity of water. Sample collection was performed during one year, from November 2013 to October 2014 on the left and right sides of Roški slap and Skradinski buk waterfalls. Modified drift nets were used for sampling, and physicochemical properties of water were measured in addition to seston sample collection. Research has shown that the difference in temperature, oxygen concentration, composition and amount of seston is caused by changes in hydrodynamics in Lake Visovac, which separates the studied travertine barriers. It was found that statistically significantly more dry matter, and its organic and inorganic components flow over the Roški slap waterfall as a result of permanent flushing of particles along the upper section of the Krka River. The overflow waters of Skradinski buk originate from Lake Visovac, which serves as a particle sink (i.e. pronounced sedimentation of particles). A higher number of organisms in drift was recorded at Roški slap, although the difference did not prove to be statistically significant, while at Skradinski buk the appearance of planktonic organisms in accordance with the lake origin of overflow waters is emphasized.