The article discusses scientific and methodological approaches to modeling and optimization of water distribution on irrigation systems (OS) of the reclamation water management complex in conditions of water supply shortage. The object of research is the theory and practice of water use of the reclamation water management complex. The subject is methods of optimization of water distribution on the irrigation system in conditions of irrigation water shortage. As the material of the work, the documents of the current regulatory and methodological framework regulating the procedures of systemic water use in the field of land reclamation, publications of domestic and foreign authors in open access, information on current solutions for the development, implementation and operation of information and communication technologies in agriculture were used. The basic research methods were: a systematic approach, optimization modeling, comparative and logical analysis. The purpose of the work is to form an effective system of algorithms, models, procedures, etc. solutions for the development of digital planning systems for efficient water distribution on irrigation systems. A feature of the proposed approaches is the possibility of making an optimal decision based on the formed set of water supply options that take into account the interests of all participants in the water use process. The hierarchical structure of a typical irrigation system is substantiated. Methodological approaches to substantiating groups of optimization criteria for mathematical modeling of the water distribution structure are considered in detail. It is shown that in order to substantiate methodological approaches to optimizing the size of irrigation areas within the OS, it is necessary to take into account the planned production volumes of agricultural products, taking into account the long-term distribution of the amount of water supplied for irrigation. The requirements, goals and criteria for choosing alternatives for water distribution planning are systematized. It is established that when solving the problem of optimizing system water distribution in conditions of water scarcity, it is necessary to take into account environmental, economic and social groups of criteria.