In a framework of monitoring the quality of surface water intended for drinking, the evolution of
eutrophication’s precursors (nitrogenous substances and phosphorus) of Ouagadougou’s third (rd) dam has
been done in the standard base period from September 2012 to December 2012. The chemical measures have
been determined by molecular absorption spectrophotometry method and the physical parameters by
electrochemical method. The physicochemical tests underlined interrelated the relationship between nitrate
content and the chlorophyll A (=0.715) and between the temperature and chlorophyll A (r=0.838). The content
of orthophosphates is feebly correlative with the chlorophyll A content of dam (r=0.171). Any significant
distinction hasn’t been observed between the orthophosphates’ mergers of four months’ studying (p=0.05). The
strongest value ( 1.3 mg /l) has been checked in the course of the month of September and the weakest value (
0.14 mg/l) during the month of November. Meanwhile, the nitrate’s content, temperature and chlorophyll A of
waters were strongest in the course of October (respectively, 6.6 mg /l ; 29.14 °C ; 0.4 ug /l) and lowest in
December ( respectively, 3 mg/l ; 23.25 °C ; 0.02 ug/l).These results showed that October’s and December’s
months are periods that cover the eutrophication’s risk of Ouagadougou’s third dam. It comes out from the
results that, water from the dam of good quality from the physicochemical stand point and covers with the
statement of trophical mesotrophy’s traces

Eutrophication, chlorophyll A, trophical statement, nitrate, temperature