Determining the most common water bodies’ boundaries, such as small rivers, in the territory of Central Russia is an actual and important task when considering land plot borders, assessing legal risks, establishing zones with special use regimes and resolving lawsuits. The purpose of this study is to develop a methodology for determining the boundaries of small rivers, the example of the Moscow oblast, RF, for land management, cadastre, and judicial expertise practice. Since, based on the Water Code, the shoreline for a river or stream is determined “by the average long-term water level during periods when they are not covered with ice”, the proposed methodology is based on standard hydrological methods (in the absence of systematic observations) and transitions from the flow rate norm Q¯ to the average long-term water flow Q¯6 during ice-free periods, using a regional coefficient. With geodetic methods, it is proposed to establish the dependence of flow rates on water level Q = f(Н), which determines the average long-term one during ice-free periods Hb, and according to a three-dimensional model of the shoreline, the position of the water body`s boundary is determined. All researches are to be carried out considering the features inherent to small rivers. With proper training of specialists, the offered methods are accessible for judicial experts, land surveyors, and cadastral engineers. They can be used in the process of determining land plot boundaries and restriction zones