Meteorological and soil temperature and moisture data for the period 1998-2005 are presented from a long term monitoring station in the central Lena River Delta at 72°N, 126°E. The investigation site, Samoylov Island, is situated in the zone of continuous permafrost and is characterized by wet polygonal tundra. The summer energy and water balance of the tundra was analyzed for the dry year 1999 and the wet year 2003. The summer water balance of the tundra was found to be mainly controlled by precipitation. The partitioning of the available energy was controlled by precipitation via the soil moisture regime, and by the synoptic weather conditions via radiation and the advection of maritime cold or continental warm air masses. In 2003, regular high precipitation resulted in a constant recharge of polygonal ponds. Of the available energy, 61% were partitioned into latent heat flux and 17% into ground heat flux; hence, the tundra behaved like a typical wetland. In 1999, low precipitation resulted in a loss of polygonal pond waters and a drying of upper soil layers. This led to lower latent heat flux (31% of available energy), higher ground heat flux (29%), and a considerably higher soil thaw depth compared to 2003. Surface and subsurface water flow had a significant influence on the tundra water balance. In 2003, the formation of new surface flow channels through thermo-erosion was observed, which is expected to have a strong and lasting influence on the hydrologie system of the tundra. Copyright 2008 by the American Geophysical Union.