Odessa region contains a unique natural complex – the Danube lakes. One of the largest is Kytai Lake. After their construction in the second half of the XX century, dams have drastically changed the ecological situation in the lakes, including hydrological and hydro-chemical parameters. 120 water samples were taken from the lake in the years 2004–2013. 1,390 measurements were taken according to 11 indicators. Our research also used historical data for 2004–2005. Studies have shown that the hydrological and hydrochemical situation in Kytai Lake deteriorated in the period 2004 to 2013. There was a marked decrease in the water transparency and a steady increase in the amount of suspended matter in the water (from 29.4 mg/dm³ in 2006 to 143.2 mg/dm³ in 2012). The salinity of the water greatly increased (up to 6200 mg/ dm³ in September – November 2012). Permanganate oxidization permanently and significantly exceeeds the maximum permissible value of BOD5. The amount of dissolved oxygen, total nitrogen, phosphorus, nitrates and pH conform to the permitted norm, although the situation with these indicators has also gradually worsened. The average annual temperature of the water was 11.4–15.8 °C, which corresponds to the temperature regime of the continental waters in the region. To improve the ecological situation in the lake, it is necessary to ensure that the pumping station supplies a stable inflow of water from the Danube, which would significantly lower the excessive salinity of the lake.