SUMMARY
The physicochemical parameters of water of four waterways crossing the town of Brazzaville were determined in upstream, the medium and downstream during the period from January 15 th to August 15th, 2015.The results of physicochemical analysis showed that the variation of of the parameters makes it possible to classify them in four group: the parameters which the quantities increase from the upstream to the downstream, the parameters which the quantities decrease from the upstream to the downstream, the parameters which the quantities increase between the upstream and the medium then decrease between the medium and the downstream and finally the parameters which the quantities remain constant between upstream and the downstream.Except the turbidity and the suspended matter which the quantities are higher than the standards of WHO, the other parameters have quantities which are in general below the standards.The nature of the crossed grounds, the nature and the volume of the rejections received by each waterways as well as the behavior of the population living near each waterway are as many elements to be taken account to explain the variation of the physicochemical and parameters.