Water is one of the most important resources on Earth and occupies three quarters of the Earth's surface. It is necessary for the life of all living beings and the maintenance of their habitats. Although Croatia belongs to the countries that are relatively rich in water, it is unevenly distributed in our area due to the different amount of precipitation that falls during the year, and due to changes in rainy and dry periods. The Mirna river basin mostly stretches through central Istria, and is characterized by torrential flows due to large altitude differences and intense precipitation. Water management in the Mirna river basin enabled water supply to the majority of the Istrian population. Water management represents human water management within the hydrological cycle taking into account economic, social and environmental factors. The goal of water resources management is the harmonization and optimization of all water systems and includes activities of planning, design, construction, management and maintenance, as well as monitoring and control. In water management, emphasis is placed on protecting life, health and property from the harmful effects of water with the purpose of permanent availability of water by optimizing economic and environmental benefits according to the principles of sustainable development.