In Slovenia, 98.7% of surface water bodies are in good chemical condition. The two water bodies are in poor chemical condition due to the excess of metals. In general, Slovenian surface waters are not loaded with priority substances in the water, but they are loaded with too high concentrations of mercury and brominated diphenylethers in fish. These are ubiquitous pollutants that are excessively present in biota both in Slovenia and in Europe.

In 2021 the Water Rights for special use of water were issued in 8385 acts (water permits, concessions), with additional more than 10.000 cases of minor spatial water uses with neglectable influence on state of water, were in the process of evidencing in the Water Book.

The total renewable amount of groundwater in shallow aquifers in Slovenia in the hydrological year 2019 was below the average of the comparative hydrological water balance period 1981-2010.

Water protection areas cover 3532 km² or 17,4% of Slovenia’s land surface in 2021. This is a slight increase, compared to 2017, but the goal of protecting the areas of all water sources for public water supply with a regulation on national level, has not been reached yet.

The Slovenian EHVZ database (Hydrography and Water Land Records) contains 67.549 watercourses with total length of 41.071 km. Total area of still waters is 24 km² and river reservoirs 31 km².

For use in water management, water land areas are delineated. Total area of water land in Slovenia is 387 km², which is 1, 9 % of continental area of the Republic of Slovenia. Marine water land area is 214 km².

Nutrients, especially nitrogen and phosphorus compounds, are important for the growth of algae and higher plants, but in high concentrations can cause undesirable changes in aquatic organisms and seawater quality. Long-term measurements of selected nutrients in the Slovenian sea show that their concentrations have decreased significantly. Therefore, the ecological status of the Slovenian Sea is assessed as good to very good based on nutrients in recent years.

Trends in annual precipitation are not as obvious as temperature trends. Changes between years and differences between regions are significant. According to climate change projections, annual precipitation will increase slightly while changes in seasonal precipitation will be more noticeable. Summer conditions are the most worrying, because less precipitation and higher temperature might result in higher frequency of droughts. In winter, more precipitation may lead to an increase in flooding events.

Precipitation is highly variable in space and time, even more than temperature, and extreme precipitation events (storms with torrential rain, hail) and drought are of particular concern. In the last two decades, Slovenia  has been observing extreme droughts and abundant precipitation resulting in floods. Drought and floods can occur even within the same year. The maximum snow cover depth and the depth of fresh snow decreased in the period 1950–2022.

2024 was the second consecutive year with above-average water abundance, with no surface water drought observed in any season. However, over the past twenty years, hydrological droughts of surface waters have become both more frequent and more intense compared to previous periods, with greater variability between individual years. Very dry and very wet years now alternate with periods of hydrologically normal conditions. The drought intensity during the growing season has become more frequent, though it has been less severe in the past decade than in the previous one.

The frequency and intensity of groundwater droughts in alluvial aquifers have been increasing in recent decades. 8 out of 10 driest years in the 1981-2025 period occurred after year 2000. Higher intensity droughts generally occur in winter while milder droughts are characteristics of autumn. However, in the Primorska region and Ljubljana basin, extreme droughts predominately occur in summer. An increasing trend in extreme drought intensity is evident between June and September, coinciding with periods of peak water demand.