In order to validate the isotopic models of the general circulation of the atmosphere ECHAM5-wiso and ECHAM6-wiso, modeling in nudging mode was made. These model data were compared with experimental data on the isotope composition (δHDO and δH<sub>2</sub><sup>18</sup>O) of precipitation for stations in the foothills of Altai mountains (52.596° N, 85.25° E) created and maintained by the Institute for Water and Environmental Problems SB RAS.
The estimation of precipitation change in the Altai (1959-2015) was carried out using the Mann-Kendall-Sneyers test. It was found that the variation of precipitation has a step change point occurred in 1980. During the first interval (1959- 1980), the trend was mostly positive, whereas during the second interval (1981-2015) it was constantly negative. The step change point of precipitation in the Altai coincides with the beginning of the «Zonal epoch Elementary Circulation Mechanisms – ECM» for Siberian sector according to the Dzerdzeevskii classification. To clarify the role of various ECM in the Altai precipitation, we calculated the contribution of the ECM, which correspond to Siberian sector, into the changes of precipitation trends. It was found that the most significant contribution into the change of precipitation regime in the Altai was provided by the «West zonal and Southern meridional» Circulation group.