The paper presents the results of the study of physical and chemical characteristics of thermo-mineral waters of the Daginsky field (Sakhalin Island) after the reconstruction of the captation structures in 2019–2020. The analysis of the data indicates the stability of the chemical composition of thermo-mineral waters before and after reconstruction works on the territory of springs. The thermo-mineral waters had a typical Cl-Na composition, and the values of the hydrogeochemical indicators did …

The paper presents the results of study physical and chemical characteristics thermo-mineral waters Daginsky field (Sakhalin Island) after reconstruction captation structures in 2019–2020. analysis data indicates stability composition before works on territory springs. had a typical Cl-Na composition, values hydrogeochemical indicators did not exceed range established by for these over multi-year period (1958–2019). However, most springs whose underwent reconstruction, significant drop surface temperatures (by 5–15°C) was recorded. indicated temperature anomaly is related to changes origin discharged or seasonal air variation. observed may be consequence decrease flow rates construction work, as well technically incorrect design thermal baths.