Abstract
The scarcity of water can result in a direct conflict between the protection of aquatic resources and water use. For many agencies, environmental flow (EF) methods are essential in environmental impact assessments and in the protection of important fisheries resources. The objective of this paper is to compare selected hydrological and hydraulic methods and determine the scientifically acceptable and cost-effective way to environmental flow within a section of a mountain river with high naturalness, on the example of the Wisłoka. In this paper, environmental flow was calculated using conventional hydrological methods: Tennant’s, Tessman’s, flow duration curve and hydraulic methods, wetted perimeter method (WPM) and method based directly on ichthyofauna habitat requirements (spawn and migration). The novelty is the combined use of the hydraulic and hydrological methods which relates to flow hydraulics based directly on ichthyofauna habitat conditions. The hydraulic methods provide lower values of environmental flow in comparison with the hydrological methods. The key issue in the use of the hydraulic methods is the choice of criteria. The development of the required set of parameters while taking into account their seasonal nature shifts the method toward habitat modeling methods. However, the scope of habitat requirements of ecosystems must be defined, including the set of aquatic organisms and watercourse type before a hydraulic method may be widely used. Being generally low-cost and simple, the methods presented in this paper can be applied in the water management legislative process.
Highlights
According to the ecosystem services concept, what man benefits from natural environment is defined as a set of the products and functions of the ecosystem which is used by the community, namely provision, regulation, support, and cultural services (Costanza et al 1997)
Determination of environmental flows by hydrological methods is based on hydrological regime indices, such as mean flow mean annual flow (MAF), low mean flows MLF, and values resulting from flow duration curves
In the light of climate changes having been taking place for some time, the analysis of characteristic flow trends for rivers has become an essential factor in the effective water management planning in a given region (Kundzewicz et al 2017; Walega et al 2016)
Summary
According to the ecosystem services concept, what man benefits from natural environment is defined as a set of the products and functions of the ecosystem which is used by the community, namely provision, regulation, support, and cultural services (Costanza et al 1997). A flow which satisfies water demand both in ecosystems and water-dependent ecosystems is termed Benvironmental flow^ (EF) It is defined as the part of natural flows which should be left in a watercourse and in flooded areas in order to keep high natural values of water ecosystems and water-dependent ecosystems (Tharme 2003). It is calculated as the difference between the observed flow (Q) and what is termed instream flow (Qn). The parameter relates to the flow in the riverbed only, which is deemed to be its most
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