This paper analyzes the basin area of the Raša river with the emphasis on the Karbune watercourse, as one of the river tributaries. The aim of the paper is to show the influence of climate changes on the balance changes in water systems and to forecast future events based on the example of the analyzed watercourse. Climate changes are becoming increasingly common, resulting in sea level rise, melting of glaciers, reduction of marine and terrestrial biodiversity, etc. As an introduction to the analysis, the basin position and its geological and hydrological characteristics were defined. Temperatures and precipitations data analysis gave an insight into the trend of movements of the mentioned parameters, which were subsequently compared with the flow data. Attempting to quantify hydrological features of watercourse at a single time scale as a fundamental basis for reflection of the necessary solutions of its protection, three characteristic periods have been determined: from 1961 to 1990, from 1991 to 2020 and from 2021 to 2050. The data used for temperatures and precipitations from 1961 to 2015 were obtained from the hydrological station in Pazin, while others were determined by three climate models: Aladin, RegCM3 and Promes. The flows were obtained by analyzing measured flow data as well as estimated values, where as an input data were used the values of temperature, precipitation and the surface of the basin area. The obtained results are presented in tables and graphs. As a conclusion, possible solutions to the future problems are mentioned. They imply the development of technologies that will enable better forecasting and adaptation to the climate. From the construction point of view it includes the reconstruction of the basin, dam construction, and other measures that will maintain the water system balance regardless of climate changes.