Abstract <p>A number of physically justified and complementary characteristics of agrocenoses are proposed, allowing for a quantitative assessment of their condition from the point of view of water resource availability and including the indicator of security of the agroecosystem, the risk of a deficit in its moisture supply, and the risk of crop failure caused by deviation of the dynamics of the water regime from the optimal, as well as the efficiency of the consumption of natural water resources by the ecosystem. A methodology for assessing the specified characteristics has been developed based on the use of the land surface model SWAP, standard meteorological information, and data on the hydrophysical parameters of the soil. This method was tested using the example of winter wheat crops under rainfed conditions at nine agrometeorological stations located in the steppe and forest–steppe regions within the grain belt of the European territory of Russia, Western and Eastern Siberia. The results of the assessment of the above characteristics for the historical period are presented, demonstrating the varying degrees of tension in the situation with water security of crops in the specified regions and the existing potential for increasing their water supply.</p>