Ecological status assessment of the rivers in Slovenia – an overview

Abstract

Adoption of the Water Framework Directive (Directive 2000/60/EC) includes ecological assessment of water bodies with biological communities. A WFD compliant ecological assessment includes ecological typology of water bodies, definition of reference conditions and classification system with five ecological classes. In this paper, an overview is given on the development of the ecological assessment system for Slovenian rivers. A special emphasis is laid on ecological river typology. 74 ecological river types were defined using bioregions or large rivers, and nine natural environmental descriptors recognised in literature as being important for river community composition in Slovenia. The rivers’ ecological status is assessed based on two biological elements, phytobenthos and macrophytes, and on benthic invertebrates, whereas an assessment system for fish is still under development. Phytoplankton rarely occurs in Slovenian rivers; therefore phytoplankton-based assessment systems were not developed. The Slovenian river classification system consists of three modules with pressure-specific assessment methods. The impact of three groups of pressures is assessed: organic pollution (saprobity), nutrient load (eutrophication) and hydromorphological alterations/general degradation. Phytobenthos and macrophytes are used to assess river saprobic and trophic status, whereas benthic invertebrates are used to assess saprobity and impact of hydromorphological alteration/general degradation. In our study, the impact of hydromorphological alterations of the Drava River was assessed using benthic invertebrates. A Slovenian multimetric index SMEIH was calculated at fifteen sampling sites. Good to bad ecological status was assessed. Moreover, at most sites within the Heavily Modified Water Bodies of the Drava River, good ecological potential was not achieved. In conclusion, mitigation measures are needed on the Drava River in order to achieve objectives of the Water Framework Directive.Sprejetje Vodne direktive (Direktiva 2000/60/ES) vključuje tudi ekološko vrednotenje stanja vodnih teles z združbami vodnih organizmov. Vrednotenje v skladu z vodno direktivo vključuje ekološko tipologijo vodnih teles, določitev referenčnih razmer in razvrščanje v pet razredov ekološkega stanja. V tem članku je podan pregled razvoja metodologij vrednotenja ekološkega stanja za reke v Sloveniji. Poseben poudarek je dan ekološki tipologiji rek. 74 ekoloških tipov rek je bilo določenih z uporabo bioregij oz. velikih rek in devet naravnih deskriptorjev, ki so bili v literaturi prepoznani kot pomembni za združbe vodnih organizmov v Sloveniji. Ekološko stanje voda vrednotimo z uporabo dveh bioloških elementov fitobentosa in makrofitov ter bentoških nevretenčarjev, medtem ko sistem na podlagi rib še razvijamo. Fitoplankton se v rekah v Sloveniji redko pojavlja, zato sistemi vrednotenja na podlagi fitoplanktona niso bili razviti. Slovenski sistem razvrščanja sestavljajo trije moduli sistemi vrednotenja, občutljivimi za stres. Vrednotimo vpliv treh skupin obremenitev: obremenitve z organskimi snovmi (saprobnost), obremenitve s hranili (trofičnost) in vpliv hidromorfološke spremenjenosti/splošne degradiranosti. Vpliv hidromorfološke spremenjenosti reke Drave smo ovrednotili z bentoškimi nevretenčarji. Slovenski multimetrijski indeks SMEIH je bil izračunan na 15 mestih vzorčenja. Ugotovili smo dobro do zelo slabo stanje. Za večino mest vzorčenja močno preoblikovanih vodnih teles reke Drave smo ugotovili, da ne dosegajo dobrega ekološkega potenciala. Na reki Dravi je treba izpeljati omilitvene ukrepe, če želimo doseči okoljske cilje vodne direktive