Estimation of pollution level of lake Yalpuh as an object of fishing purpose

Abstract

The work offers estimation of Lake Yalpuh's water quality for a long period as a fishery object. The preliminary analysis of the dynamics of water quality indicators change showed that there was a decrease of concentrations of almost all quality indicators during the period of the study (2003 - 2017).
 According to the results of the estimation, the water quality of Lake Yalpuh in the top section was characterized by the "very dirty" category, the quality class was marked as IVc-IVd. Most often such indicators as dry residue, magnesium, chlorides, sulfates were taken as limiting indicators of pollution. During the research the quality of lake water was did not change significantly. The maximum level of pollution was observed in 2004.
 The water of the lake at the water intake section was also characterized by the "very dirty" category, the quality class was marked as IVb - IVd. Most often such indicators as magnesium and sulfates were taken as limiting indicators of pollution. During the period of research there was a tendency towards a decrease of the lake's level of water pollution. The maximum level was observed in 2003 – 2004.
 The waters of the lake in the 13th km section was characterized by the "dirty" (quality class ІІІa-ІІІb) and "very dirty" (quality class IVa-IVc) categories. Most often such indicators as magnesium and sulfates were taken as indicators of limiting pollution. Significant fluctuations of the level of the lake water pollution were observed. The maximum level was observed in 2004.
 The general analysis of the dynamics of change of the combinatorial index of water pollution in Yalpuh Lake at three sections for 2003 - 2017 showed that the maximum level of water pollution in the lake was observed at the first section (top), the minimum – at the 13th km section. There is a tendency towards decrease of the value of the combinatorial index of pollution.
 Virtually the entire territory of the Yalpuh River Basin is located at the southern part of Moldova where the state of wastewater treatment is unsatisfactory. Therefore, the level of pollution in the lake often exceeds the permissible standards. In recent years, due to decrease mineral fertilizers and pesticides use in Moldova's agricultural sector, the situation improved though.