[en] An artificial reservoir at the territory with density of contamination with ¹³⁷Cs 17.4-54 and ⁹⁰Sr 0.67-2.47 Ci/km² was investigating. In July 1991 activity of water on ¹³⁷Cs has increased in comparison with May 1990 from 0.31 to 0.74 Bq/l, and activity on ⁹⁰Sr has not changed and equals 0.46 Bq/l. The values of coefficients of accumulation for the objects investigated are close (n*10⁴ for ¹³⁷Cs and n*10² for ⁹⁰Sr). The investigations have shown that as a general indicator of radioactive contamination of water Elodea Canadensis Rich. is desirable to use, which is widely distributed over the reservoirs of Belarus and has large period of vegetation. 3 refs., 1 fig., 1 tab