The article is devoted to the actual scientific and practical problem of improving methodological and methodical approaches to the evaluation of design solutions in the water management and land reclamation industry based on the ecological and economic principles in conditions of uncertainty. The current stage of the development of the water management sector in Ukraine is characterized by a combination of past negligence and the present energy, food and water crises, as well as global climate change. To solve these problems, it is necessary to reform organizational-economic relations in the industry, including new sources and forms of financing for water management and land reclamation projects, introduction of new environmentally advanced technologies, and the improvement of the existing ecological and economic evaluation of investments. Based on scientific and methodological recommendations used for evaluating the effectiveness of investment in various spheres of economic activity, the authors developed and implemented an improved methodology for the evaluation of water management and land reclamation projects. It is based on methodological approaches that cover such elements as the variety of options, changes in the value of money over time, specific project implementation environment, including the impact of weather, climate and environmental factors on project performance, multilevel and gradual evaluation of a project against specific criteria and according to stages of the project cycle. The method was tested during the reconstruction of a rice irrigation system in the steppe zone of about 3000 ha in Ukraine. Economic results, namely the deterministic payback period and investment return index confirm that the proposed mechanism, unlike the traditional one, increases the economic and environmental feasibility of water management and land reclamation projects. Therefore, it stimulates investment in the land reclamation sector.