Entropy approach to assessment of the ecological state of a water course

Purpose. Water quality assessment of the Dnipro Reservoir using the entropy index. Methods. Analytical-synthetic method, geo-informational (cartographic modeling), analysis of information sources, entropy analysis. Results. It was established that the water does not meet the upper limit of the 1st quality class according to DSTU 4808:2007 by all parameters except BOD5, COD and suspended matter. There is a decrease in the level of BOD5 at posts in the city of Dnipro, which indicates the entry into the watercourse of substances that inhibit biochemical processes (t4 and t5) and a gradual increase of this indicator at the exit from the city and further downstream, which indicates the entry of organic substances. The oxygen content decreases in the part of the watercourse located in the city (t4 - t6) and increases in the middle and lower part of the reservoir. There is also a trend of growth of sulfates, nitrogen compounds, phosphates, SPAR and COD for control points located within the city of Dnipro. The highest values of the entropy index of water quality are characteristic of points t2 (0.5444), t7 (0.6264) and t8 (0.5322). These control points are located at a considerable distance from industrial centers, so pollution caused by agricultural production probably plays a decisive role in the formation of water quality. The lowest value of the index (0.3889) is characteristic of item t1 - s. Shulgivka, after GVK Dnipro-Donbas. Conclusions. It was established that the main water pollutants are nitrites, nitrates, phosphates and suspended solids. It can cause a negative impact on health due to mutagenic and carcinogenic effects, and also accelerates the eutrophication of the water body. A negative impact of agro-industrial production on the ecological condition of the Dnieper Reservoir is observed. The value of the entropy index of water quality ranges from 0.3889 to 0.6264.