Slovenia: Assessment and Provision of Environmental Flows in Mediterranean Watercourses (#328)

In Slovenia, water is extracted for drinking water, energy, fish-farming, irrigation and technological purposes. In order to avoid over-extraction, an Environmental Flow framework has been implemented, assessing within what limits water can be extracted, using hydromorphological, hydrological, hydraulic and ecological criteria. The case shows that it is important to combine policy decisions with expert evaluations. 


On the rivers and streams, there are water abstractions for drinking water, energetic use, fish-farming, irrigation and technological purposes, many are still planned. Great diversity of hydromorphological types of rivers in Slovenia and biological diversity are the reasons for EF (Environmental Flow) determination for every river separately. 

The main focus of EF is the quantity of water which preserves ecological balance in the river and in the riparian zone. The changes can be only within the limits, in which the stream is able to preserve its own character and function of preservation of the natural balance.

EF is determined before every intervention in the stream, which can have an effect on the water regime, on the structure and on the function of the stream ecosystem. As the most important criteria for evaluation of EF hydromorphological, hydrological, hydraulic and ecological criteria were chosen.

According to the criteria two different methods for determination of EF are used: hydrological and ecological method. Hydrological method is timely short in comparison with ecological method. For the last one, inventory of flora, fauna and habitats has to be carried out and landscape evaluation has to be done.

Both of the methods were applied on lowland, karst and alpine streams in Slovenia. The intention is to apply this methodology on more rivers, according to different water users, amount of water abstraction and ecoregions.

Lessons learned

  • EF should be determined by experts before any intervention in the river, which effect the flow regime; 
  • the state as the owner of natural resources has to assure the supervision on water abstractions and assurance of EF.

Importance of the case for IWRM

The case shows that it is important to combine policy decisions with expert evaluations. One of the methods is assessment of environmental flow. It combines hydromorphological, hydrological and ecological criteria to evaluate absorption capacity of the water cycle.

Photo credit: Urška Oset