The paper evaluates the possibility of calculating evapotranspiration and gross primary production using a coupled biophysical Penman-Monteith-Leuning model for large catchment areas. In particular, the paper considers the application of the Penman-Monteith-Leuning model for the Lake Ladoga catchment. The theoretical foundations of the model,its flowchart, and the possibility of accessing it through the interface of the cloud platform for the analysis and processing of geospatial data Google Earth Engine are outlined. The model uses MODIS satellite images as input data, from which it receives the properties of the underlying surface. For meteorological data, the model uses the reanalysis model GLDAS. The land cover is classified according to the IBCG classification. Based on the Penman-Monteith-Leuning model, maps of the geospatial distribution of evapotranspiration and its constituent components (vegetation transpiration, soil evaporation, interception from vegetation canopy) and gross primary production in the Lake Ladoga catchment were obtained. The results indicate that evapotranspiration and gross primary production were the greatest in the south of the Lake Ladoga catchment, in areas of mixed forests. For the period from July 2002 to December 2017, there was no significant change in gross primary production, evapotranspiration and its components. For all components of evapotranspiration and gross primary production, seasonality associated with the growing season in the region is observed. The model outputs are consistent with the data on evaporation reported by other authors. The Penman-Monteith-Leuning model is hence fit for application to the Lake Ladoga catchment. The results of the study can be used for efficient water management, in particular for the reclamation of agricultural land in the study area.