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[VD07] Phosphorus in lakes
State

Key message
Neutral

Nutrient over-enrichment remains the key environmental challenge for lakes and reservoirs in Slovenia. For the assessment period 2014–2019, only 4 of the 11 lake water bodies achieved good or high ecological status. Recent annual data indicate no signs of improvement, and in some lakes total phosphorus concentrations are even rising. The main pressures are linked to human activities, especially inappropriate discharge of municipal wastewater, intensive agriculture in the catchments, and fisheries.

Charts

Figure VD07-1: Annual average concentration of the total phosphorus (µg P/L) in lakes and reservoirs
Sources:

Unified database of water quality monitoring, Slovenian Environment Agency, 2025 (10/09/2025)

Show data
Bohinjsko jezero[µg P/L] Blejsko jezero[µg P/L] Velenjsko jezero[µg P/L] Klivnik[µg P/L] Mola[µg P/L] Vogršcek[µg P/L] Šmartinsko jezero[µg P/L] Slivniško jezero[µg P/L] Perniško jezero[µg P/L] Ledavsko jezero[µg P/L] Gajševsko jezero[µg P/L]
2006 4 15 120 8 33 88 102 101
2007 5 13 94 9 19 9 95 85 192 135 222
2008 4 12 30 10 14 9 49 29 126 104 89
2009 4 13 25 15 15 10 160 38 252 137 122
2010 4 12 55 12 11 8 46 23 180 70 112
2011 5 10 53 9 13 14 36 34 224 64 99
2012 5 13 49 12 18 16 30 42 307 100 110
2013 6 11 60 9 13 15 37 50 343 123 130
2014 6 13 87 9 12 14 51 49 88 83 83
2015 5 13
2016 5 12 83 12 17 12 46 37 125 58 134
2017 5 13 19 52 56 387
2018 5 12 82 12 16 117 117
2019 5 11 19 48 55 264
2020 5 14 75 11 16 288 222
2021 5 14 48 37 247
2022 5 13 55 200 224
2023 4 12 13 50 59 230
2024 6 11 53 18 25 169 205
Figure VD07-2: Average concentration of the total phosphorus (µg P/L) in lakes and reservoirs in selected RBMP periods
Sources:

Unified database of water quality monitoring, Slovenian Environment Agency, 2025 (10. 09. 2025)

Show data
1. RBMP[µg P/L] 2. RBMP[µg P/L] 3. RBMP[µg P/L]
Bohinjsko jezero 4 5 5
Blejsko jezero 13 12 12
Velenjsko jezero 62 55 84
Klivnik 10 11 11
Mola 17 14 15
Vogršček 9 13 16
Šmartinsko jezero 59 60 49
Slivniško jezero 57 39 49
Perniško jezero 135 232 216
Ledavsko jezero 114 96 86
Gajševsko jezero 137 109 111
Figure VD07-3: The trophic status assessment of lakes and reservoirs based on phytoplankton in selected RBMPperiods
Sources:

Unified database of water quality monitoring, Slovenian Environment Agency, 2025 (10. 09. 2025)

Show data
1. RBMP 2. RBMP 3. RBMP
Bohinjsko jezero 0.96 0.94 0.94
Blejsko jezero 0.58 0.58 0.59
Velenjsko jezero 0.52 0.62
Klivnik 0.71 0.66
Mola 0.70 0.71
Vogršček 0.60 0.69
Šmartinsko jezero 0.47 0.45
Slivniško jezero 0.44 0.42
Perniško jezero 0.25 0.24
Ledavsko jezero 0.34 0.29
Gajševsko jezero 0.32 0.28

Methodology

Other sources and literature

  1. ARSO, 2015. Ocena stanja jezer v Sloveniji v letu 2014. Ljubljana, Ministrstvo za okolje in prostor, Agencija RS za okolje. URL: http://www.arso.gov.si/vode/jezera/Poročilo JEZERA _2014.pdf (2. 2. 2021).
  2. OECD, 1982. Eutrophication of Waters. Monitoring, Assessment and Control. Paris, Organisation for Economic Co-Operation and Development.
  3. Metodologija vrednotenja ekološkega stanja jezer na podlagi fitoplanktona, Ministrstvo za okolje in prostor, 2016
  4. Metodologija vrednotenja ekološkega stanja jezer na podlagi fitobentosa in makrofitov, Ministrstvo za okolje in prostor, 2016

Last modified
18.11.2025
Author(s)

Tadeja Šter, Nataša Dolinar, Slovenian Environment Agency