Thermokarst lakes and basins are major components of the ice-rich permafrost landscapes in East Siberian coastal regions. One of the major control factors of thermokarst lake development is the local water balance. Variations in environmental and climate conditions due to climate change might have severe impacts on the water balance. Higher evapotranspiration and an increased active layer thickness could enhance the water flow and thus favor the thermal degradation of the tundra landscape. In this study we quantified precipitation, evapotranspiration, runoff and storage of a thermokarst lake on Kurungnakh island. The island is located in the central part of the Lena River delta, northern Siberia and underlain by continuous, ice-rich permafrost to about 400-600m depth. The investigated lake has a surface area of approximately 1.2 km² with a maximum depth of about 8 m and a volume of about 4x106 m3. Field measurements of the water balance components were conducted in the period from August 2014 to end of July 2015. Precipitation was recorded by an automatic rain gauge, at a nearby site on Kurungnakh Island. The outflow of the lake was determined with an automatic sensor on a RBC-flume. The evaporation of the thermokarst lake was calculated by using water temperature of the lake, climate data from weather stations on Kurungnakh Island and the neighboring Samoylov Island. The lake water storage was measured using an automated water level sensor. A previous study (Niemann, 2014) investigated only the summer balance (August 2013) of the lake and showed that evaporation dominated the water balance during this time period. Here we analyzed the seasonal and annual water balance components (precipitation, evaporation, runoff, change in storage) of the lake and the contribution of snow cover to the water storage.