Vertical distribution of microbial pollution (biological stratification) in Large reservoir, Case study: Sabalan Dam

The main purpose of the research is to investigate the relationship between pathogenic mirco-organisms (total coliforms (TC) and fecal coliforms (FC)) with physical and chemical parameters of water in different depths of reservoirs. Samples were taken from different depths of the dam reservoir in June,, July and August, when the water was in maximum temperature , pH, TC, FC, electrical conductivity (EC), pressure (P), Total phosphorus (TP), total dissolved solids (TDS), dissolved oxygen (DO) and temperature (T) were measured. Preliminary results showed that pH, DO and T parameters decreased with increasing depth in the water column, while EC, TDS and TP increased. The results obtained from multivariate statistical analysis methods revealed that TC and FC were affected by P and TDS changes. By moving from the surface to the bottom of the dam reservoir, the distribution of the coliforms decreased, which is unbalanced, and no specific pattern of coliform distribution can be considered. Based on the analysis of the relationships, it was found that 58% of total coliform and 59% of fecal coliform changes were predictable if the total soluble and pressurized solids were quantified. Also, by Pearson correlation analysis, it was determined that total coliform and fecal coliform, in none of the four levels, were correlated with total soluble solids and pressure parameters, and none of these parameters had a significant direct effect on them. As a result, fecal coliform and total coliform are directly related to T, Do and pH and inversely related to EC, TDS, and strain.