On the basis of the analysis of wide temporal monitoring data, a forecast of the integrated hydrochemical indicators of the waters of the Inhul river (Ukraine) was carried out. The performed analysis was also the basis for the determination of a mathematical model of natural fluctuations of the indicators studied. The determined sinusoidal dependence of the integrated water quality indicators allowed determining the average time of fluctuations concerning the processes of self-organisation of river waters. In practice, the developed mathematical models may constitute a valuable support and supplement to the existing models in the field of prediction of self-organization processes of river waters. They may also contribute to even more effective minimization of undesirable effects of anthropogenic impact on aquatic ecosystems.

This paper presents results of the research on the effectiveness of entrapping sediment matter in newly designed sediment traps. Four traps, characterized by different geometrical and construction parameters, were analyzed. The assessment of the operation of the traps was made on the basis of research work conducted in situ in a small retention reservoir located in Blizne, south-east Poland during summer 2017 and 2018. Under environmental conditions present during the research, trap number 2 emerged as the most effective. It was characterized by a height to diameter ratio equal to 6.06, as well as innovative design thanks to the presence of a dual-chamber cylindrical vessel with a sedimentation funnel ending in a deflector. The proposed construction solution ensured optimal, stable operation of the trap. This trap is more effective in entrapping sediment matter than the simple tools described in the literature so far. In addition, it can be used not only in reservoirs, but also in seas and oceans. Such traps can be used to study the sedimentation rate in various water ecosystems, and also the entrapped sediment can be analysed in a qualitative manner to determine its role in the distribution of pollutants deposited in the sediments of aquatic ecosystems.Hydrology 2019, 6, 48 2 of 11 by a high sorption capacity. Hence, the most intensive sedimentation of suspended particles in water occurs in spring and summer [8]. Moreover, shore erosion and the transport of suspended particulates affect the re-deposition of sediments in a reservoir [9][10][11].Under certain conditions, soil particles (mainly clays and loam) from shore erosion can combine to form aggregate at a much greater rate of descent than elementary particles. The formation of aggregate is dependent on the physical, chemical and electrochemical conditions characterising liquids, as well as the properties of elementary particles, the content of organic matter and the water flow rate [12,13].Knowledge of the specificity and deposition rate of suspended particles in water at the reservoir bottom is of great importance to ensure a given reservoir's proper use. The sediment trap system can deliver in situ information about surficial sediment layers, which are difficult to explore with traditional sampling tools [14].Over the past few decades, various tools and techniques have been developed to determine the streams of sedimentary particles in water environments. The oldest and simplest method is the sediment trap. However, despite its simplicity, this method poses multiple problems, including methodological problems relating to the interpretation of collected data, design problems with the adaption of geometric parameters to hydrological conditions, and difficulties related to the fixing of the trap in the reservoir.

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This paper presents research on the influence of suspended sediments on selected aspects of a reservoir’s functioning. As the amount of sediment suspended in water (SS) there was found to correlate significantly with sedimentation rate (Us), it was possible to develop a function allowing the rate of accumulation of sediments to be predicted by reference to known amounts of suspended sediment. The latter factor was also shown to correlate significantly with the content of organic matter in suspension (OMSS), in sediment captured in a sediment trap (OMS), and of bottom sediment (OMSB). Analysis of amounts of suspended sediment can provide for estimates of total loads of organic pollutants deposited in the sediments of a reservoir. A further significant correlation with SS was noted for the concentration of total phosphorus in water (TPW), confirming the importance of internal production where the circulation of this biogenic substance in a reservoir ecosystem is concerned. Analysis of stable carbon isotopes in turn showed that entrapped sediments were depleted of—or enriched in—13C, in line with whether concentrations of total P in those sediments (TPS) were at their highest or lowest levels. This dependent relationship may thus be of key importance in assessing sources of phosphorus, as well as in forecasting concentrations present in reservoir sediments. The results obtained make it clear that sediments suspended in the water of a reservoir unify phenomena and processes ongoing there, between elements of the water-sediment system.