Water consumption in Slovenia represents a relatively small proportion of the annual gross water outflow from the country. In 2019, the annual WEI+ index was around 3%, and same 3% compared to the periodic average of water availability. The Long-term Annual Average Water Exploitation Index shows a slight decrease, but the trend is not statistically significant.

In recent years, the amount of wastewater treated by secondary or tertiary treatment processes increased, while primary treatment processes have closed. The amount of wastewater treated through secondary treatment processes increased by 150 % since 2000 or from 30 million m3 (in 2000) to almoust 45 million m3 (in 2019). There were almost no tertiary wastewater treatment processes in Slovenia in 2000, and in 2019, 72% of wastewater or 113 million m3 of wastewater was treated by tertiary process.

The above-average runoff years of 2013 and 2014 were followed by a below-average year in 2015 and a period of average annual runoff from 2016 to 2021. In 2022, runoff levels were again below average, while 2023 saw a return to above-average conditions. Based on the annual river balance, 2023 ranks among the wettest years in the history of hydrological measurements. Between 1961 and 2023, the most water-abundant years were 2013, 2014, and 2023. In contrast, the driest years were 1983, 2003, 2007, 2011, 2015, and 2022.

Groundwater in intergranular aquifers in Slovenia is most affected by nitrate pollution, particularly in northeastern Slovenia. In contrast, groundwater in karst and fissured aquifers is less impacted due to geographical conditions, lower population density, and a smaller proportion of agricultural land.

For the period 2019–2024, poor chemical status was identified in the water bodies of the Savinja, Drava, and Mura basins. The main cause of poor chemical status in all water bodies was nitrate, with atrazine additionally contributing in the Drava basin.

In Slovenia, nutrient overloading is still the basic problem concerning lakes and reservoirs, and from 2006 to 2019, no improvement is observed. In the assessment period 2016–2019, only 4 out of 11 lake water bodies were determined to be in good or very good trophic status. Overloading of lakes with phosphorus is usually a result of inadequate wastewater drainage and intensive agriculture in the watershed area.

In 2022, drinking water monitoring was carried out for 93.8% of Slovenia's population across 863 supply zones that serve 50 or more people. Large and medium-sized zones, serving more than 500 inhabitants, generally maintain a good water quality. The greatest issues are found in smaller zones (50-500 inhabitants) with a higher percentage of fecally contaminated samples. Chemical contamination was detected in two zones, mainly due to exceeded levels of lead and the pesticide desethyl-atrazine.

Inland bathing water quality in Slovenia is good and comparable with bathing water quality in other European countries.

Values ​​of parameters used for monitoring the organic loading of rivers have greatly reduced since 1996, however ammonium levels remain much higher than natural background. The observed reduction in organic loading corresponds to an increase in the share of population whose wastewater is treated at wastewater treatment plants. The nutrient loading varies considerably among rivers of the Adriatic and the Danube river basins.

In 2024, we began reporting on the chemical status of groundwater for a longer six-year period, in line with the reporting cycle under the Water Framework Directive. Based on this assessment, the state adopts measures to improve water quality.

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.