VERTICAL FLUCTUATIONS OF KEY PARAMETERS OF THE SELF-PURIFICATION IN THE “MIDDLE ISKAR” CASCADE’S RESERVOIR LAKATNIK

Abstract

Iskar River is a highly modified ecosystem in the part Prokopanik-Gabrovnitza from the newly built small Hydroelectric Power Plants (HEPPs) in the “Middle Iskar” cascade. A 12-year monitoring program studies the ecological status of the river and gradually under construction, putting into operation the HEPPs and associated dams. This article covers the period when the one dam at HEPP Lakatnik were constructed and started its exploitation. The aim is to determine the influence of the vertical fluctuations of the key hydrochemical and microbiological indicators of the water column on the self-purification processes. On the base of these parameters the assessment of influence of technological exploitation, morphology and depth of water column on biotransformation processes has been made. An additional valuable information for the connection of self-purification potential and synchronize functioning of reservoir has been extracted by means of our results. In the micro-dam Lakatnik microbiological (aerobic heterotrophic bacteria and endo-bacteria) and hydrochemical parameters (content of nitrate, nitrite, ammonium and phosphate ions, chemical oxygen demand, content of oxygen, dissolved and unsoluble suspended solids, total dry weight) were investigated in the following water horizons: Lakatnik – 0, –1, –2.5 and –3.5 m. The used methods were according to the Bulgarian State Standards, therefore, our results are oriented to an assessment of the water quality in correspondence with existing regulations. These results indicate that the available
local fluctuations are not significant. All data are in compliance with the existing ecological, hydrological and technological features of the studied water bodies, which plays an important role for the following: 1) Discovering of mechanisms and possibilities for increasing the efficiency and effectiveness of the monitoring strategy; 2) An adequate decision-making process in the technological exploitation of the Middle Iskar cascade.