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Influence of Exploitation of Hydroelectric Power Plants Lakatnik and Svrazhen on Self-Purification Potential of Iskar River in 2011
... The complex of Endo bacteria is an indicator of faecal contamination and biodegradation potential. These two groups of microorganisms are important for the ecosystem functioning and formation water quality [17,18] and their dynamics in the water of the reservoirs during the studied seasons is given in Figure 5. ...
The Middle Iskar cascade is situated along the middle course of the Iskar River (Bulgaria) after the capital city Sofia and has three small hydroelectric power plants that were put into operation by the end of 2012. The aim of this study was to evaluate the self-purification potential of water in the reservoirs of these plants as an important and necessary condition for their ecological functioning. The assessment was made by hydrochemical parameters (dissolved suspended solids, insoluble suspended solids, total suspended solids, nitrites, nitrates, ammonium, phosphates, chemical oxygen demand, dissolved oxygen) and microbiological parameters (aerobic heterotrophic bacteria and bacteria growing in an Endo medium) and covered a period of three years (2010, 2011 and 2012). Standard methods were applied, mainly colorimetric and microbiological cultivation methods. The obtained results showed high levels of some of the tested indicators during 2012. In the section of the Middle Iskar cascade a high self-purification potential was observed in the reservoirs which maintain good water quality.
... Shallow artificial water bodies, such as small dams in the walls of cascade of small HEPPs "Middle Iskar" suffered the most powerful change in the level of its waters. This leads to an acceleration of biological processes (Lincheva, 2012). ...
Iskar River is a highly modifi ed 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 infl uence of the vertical fl uctuations of the key hydrochemical and microbiological indicators of the water column on the self-purifi cation processes. On the base of these parameters the assessment of infl uence of technological exploitation, morphology and depth of water column on biotransformation processes has been made. An additional valuable information for the connection of self-purifi cation 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 fl uctuations are not signifi cant. 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 effi ciency and effectiveness of the monitoring strategy; 2) An adequate decision-making process in the technological exploitation of the Middle Iskar cascade.
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