Valley of Geyser Reservoir and Kikhpinych Volcano form a joint magma-hydrothermal system, which is characterized by recent (500-1500 years ago) eruptions of Kikhpinych volcano and subcaldera formation; shallow magmatic activity in area of 15 km2 beneath, meteoric water and magmatic components (Cl, CO2) recharge and convective thermal outflow from Kikhpinych structure in adjacent Valley of Geyser, two catastrophic landslides/mudflows of 2007 and 2014 were possibly triggered by Kikhpinych magmatic injections. Chloride tracer, chemical geothermometer and local thermalhydrodynamic modeling methods were applied to update hydrothermal outflow parameters (water, CO2 and chloride mass rates, geyser erupted volumes, cyclic component of mass discharge, seasonal variations). Then TOUGH2-EWASG model was used to reproduce 5000-year thermal-hydrodynamic history of the magma-hydrothermal system, followed by cold water infiltration aftermath of catastrophic events 2007 and 2014. This model explains: (1) Quasi-stationary conditions of enormous heat (180 MW) and mass (250 kg/s) discharge achieved in few thousand years; (2) Chloride discharge rate drops as a response to seasonal cold water infiltration; (3) Long term chloride concentration drops and geyser erupted volume rises after infiltration period starts.