Assessing lake eutrophication in Van Quan new residential area

Abstract

The Van Quan urban lake cluster consists of two artificial lakes located in the new urban area of Van Quan (Ha Dong, Hanoi), which are Van Quan Lake and Than Tho Lake. This study aims to determine the trophic status of this lake cluster and the changes in the trophic state index (TSI) over space and time based on in situ datasets of Chlorophyll-a (Chla) concentration, total phosphorus (TP) concentration, and water transparency (SD) obtained from 15 sampling points during 4 surveys from December 2020 to June 2022. The results showed that both lakes were in a state of eutrophication with TSI values > 74 at all measurement times. TSI values varied slightly by season, with higher values in the rainy season (June) and lower values in the dry season (December). In terms of spatial distribution, the TSI value of Van Quan Lake was always higher than that of Than Tho Lake. TSI values were also generally higher at the entrances of drainage channels along the 19/5 street than at other sampling points. High eutrophication levels are the main cause of frequent occurrences of algal blooms in this lake cluster.