Abstract
River water resources provide a wide range of necessary ecosystem services, including regulating, provisioning, supporting and cultural services. Ecosystem services are linked to an appropriate level of functionality of river water resource processes, which can be connected with river basin environmental objectives. Environmental objectives can be achieved only if appropriate flow and sediment regimes and related river morphology quality are guaranteed. The obligation to define environmental flow (E-flow) in the European Union Water Framework Directive European (WFD) is not explicit, and the implementation of the WFD is more focused on water quality. Considering the specific climatic, hydrographic and hydrological conditions and the definition of E-flow, each EU country has developed procedures for their investigation and determination. In the Republic of Croatia, no methodology has been elaborated, nor is there any legal regulation to define E-flow downstream of a dam or water intake site. This paper presents the significant pressures that have affected the transboundary rural Sutla River basin between Croatia and Slovenia. These pressures can cause changes in the hydrological regime and biological elements of water quality. The holistic approach defines the E-flow for a profile on the Sutla River by linking hydrological, morphological, and ecological characteristics based on the exploration of the Sutla River and its biological communities. The full implementation of a holistic approach and the transition to Level III of the E-flow definition requires the enhancement of exploratory hydrological and biological monitoring that enables the use of habitat modelling. Doi: 10.28991/cej-2020-03091611 Full Text: PDF
Highlights
Flow alteration is among the most serious threats to freshwater ecosystems
The risk of not achieving good water status – GAP – for the hydro-morphological pressures and status was prepared based on existing studies [28, 30], assessments prepared for specific goals and periods without a regular hydro-morphological monitoring programme
While much effort has been dedicated to the development of these methods, the biological effects of environmental flow regulations have been evaluated in only a small number of cases
Summary
Natural seasonal increasing and seasonal decreasing water levels shape aquatic and riparian habitats, provide migration and spawning conditions, and enable rivers to function properly [1, 2]. Altering natural flow by damming, diverting or channelling water has serious impacts on biodiversity and ecosystem services [3]. River water resources provide a wide range of Ecosystem Services (ESs) that can be classified into four main categories: (i) Food services, i.e., products derived from ecosystems; (ii) Regulation services, i.e., processes and functions; (iii) Habitat services; and (iv) Cultural services [4]. ESs are linked to the appropriate level of functionality of river water resource processes, which can be explained by the environmental objectives of a river basin [5]. The obligation to define an environmental flow in the WFD [6] is not explicit, and the implementation of the WFD is more focused on water quality
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