It has been substantiated in the article that the assessment of the programs and projects on the regional irrigation systems development should be based on the economic analysis, which will allow to judge either the investment project will positively contribute to the economic growth and the economic progress of the country or not. During the conduction of the economic analysis of the strategy on the irrigation system development it is advisable to consider externalities appearing in the following subsystems: the household, the plant growing, the animal husbandry, the fish industry, the water resources and the land resources. Besides that while conducting the evaluation it is quite necessary to take into account the expected damages connected with the accidents: the damage of people, the destruction of constructions, territories flooding, the damage of sowings, the violation of the natural environment, etc. All these consequences of the implementation of the irrigation projects should receive cost evaluation and should be taken into account during the calculation of cash flows. The method of cash flows modeling of the project on the regional irrigation systems development, allowing to take into account the influence of the investment projects on their surroundings in the subsystems: the household, the plant growing, the animal husbandry, the fish industry, the water resources, the land resources, the natural landscapes, etc., has been presented in the article.
