ИСТИНА

For the last two decades on a number of Hydro Units in Western Yakutia, we observe seepage process compromising their secure. We present geophysical methods for verification of permafrost state near Sitikan and Vilyui Hydro Units. Complex includes electric, electromagnetic, ground penetrating radar, hydro location, thermal and radiowave (down-hole) measurements. Ground level and down-hole geophysical survey focused on detecting thawing zones (talik) in dam, its flank and tail-water zone. Long-term geophysical monitoring shows up spatial-temporal permafrost evolution and talik development in the flank shore of Sitikan dam. Detecting of inflow zone and seepage velocity performed for right-bank contiguity of Vilyui HPS-1. Alongside with field studies the numerical evaluations of conditions of originating permeable talik-zones (thawing) in a board zone of dam, was down. The non-steady problem of heat-mass transfer in fractured-porous saturated frozen Stratum, interlaying in frozen impermeable adjacent Strata is proposed. Numerically analyzed conditions causing origin and development of talik near reservoir: annual air temperatures, snow cover, annual water temperature in storage basin with depth, permeability evolution in frozen soil. Proposed model can be used for analyzing more complex situation