Necessity of water treatment to meet lake water quality goals in Chitgar Lake

Abstract Bayat J, Hashemi SH, Nikzad MF, Talakesh SMR. 2021. Necessity of water treatment to meet lake water quality goals in Chitgar Lake. Lake Reserv Manage. 37:160–169. Managing urban lake water quality to prevent algae blooms is important for tourism at Chitgar Lake, which is a shallow artificial lake created for recreation in northwest Tehran City, Iran. Its water quality is influenced by the Kan River as its water source, as well as by peripheral activities and bird excrement. This study investigates the effectiveness of different water quality management practices including restricted water intake rules and water treatment from April 2013 to April 2020 to improve the water quality of the lake in order to limit algae blooms. The nonparametric Mann–Kendall method and the Sen function were applied to decipher trends and assess impacts of the practices. Despite intake water control, the trend analysis showed that chlorophyll-a and total phosphorus had increased after the opening of the lake in 2013. However, this incremental trend was greatly reduced after commissioning a treatment plant for improving water quality. The treatment system improves the quality of diverted Kan River water during winter lake refill and is used to treat lake water during the rest of the year. The specific characteristics of the lake and the Kan River prevent achievement of target water quality without water treatment.