— Within the framework of this work, using a three-dimensional numerical model of the general circulation of the Martian atmosphere MAOAM (Martian Atmosphere: Observation and Modeling), also known as MPI-MGCM (Max Planck Institute Martian General Circulation Model), we simulated the planet’s hydrological cycle during the 28 and 34 Martian years (MY28 and MY34) dust storm seasons. A quantitative assessment of the photodissociation of water vapor under the influence of solar radiation at the Lyman-alpha wavelength has been carried out. The simulation results are compared with individual profiles obtained with the Atmospheric Chemistry Suite (ACS) spectrometer installed on the ExoMars Trace Gas Orbiter (TGO) spacecraft. The MAOAM model has a spectral dynamical core and successfully predicts the temperature regime of Mars through the use of physical parameterizations that are characteristic of both Earth and Martian models. The hydrodynamic block of the model includes the transfer scheme, microphysics of water vapor and ice, heterogeneous nucleation, sedimentation, photodissociation, and exchange of water with the surface. Studies show the effect of dust storms on both the total water vapor content in the atmosphere and its vertical distribution. More intense pumping of water vapor into the upper atmosphere during dust storms provides more intense photodissociation of water vapor (in some seasons up to 6.5 tons per second in total in the entire atmosphere). The strongest photodissociation is observed at heights of 50 to 80 km for MY34 and 70 to 80 km for MY28. The dissociated water vapor can then potentially become a source of hydrogen dissipation into space, followed by a decrease in the mass of water on the planet.