Combined use of the hydraulic and hydrological methods to calculate the environmental flow: Wisloka river, Poland: case study

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.

A Comment on Chinese Policies to Avoid Negative Impacts on River Ecosystems by Hydropower Projects

“…Researchers are encouraged to discriminate between methods, assess their applicability and choose the most appropriate method. Most of the previous [31][32][33] studies have carried out environmental flow calculations for specific projects. How to reduce the uncertainty and improve the rationality and accuracy of the evaluation results is worth further discussion.…”

Uncertainties associated with environmental flow metrics

“…A recent study, Theodoropoulos et al (2018) found that, among the hydrological methods applied, most resulted in flows lower than those obtained using ecosystem‐based methods. However, hydrological environmental flow methods remain the most widely used and least costly methods (e.g., Caissie et al, 2015; El‐Jabi & Caissie, 2018; Ksiazek et al, 2019; Tharme, 2003) and therefore uncertainties surrounding flow metrics used in hydrologically based methods remain an important yet less studied aspect of these methods.…”

Development of an Optimal Model for the Xiluodu-Xiangjiaba Cascade Reservoir System Considering the Downstream Environmental Flow

“…More than 200 methods of determining environmental flows have been developed, and they can be classified into four principal groups: (1) hydrological methods [47,48], including the Tennant, 7Q10, flow duration curve (FDC), aquatic biological base flow, and RVA methods [49]; (2) hydraulic methods [50,51], including the wetted perimeter and R2CROSS methods; (3) habitat simulation methods [52], including the instream flow incremental methodology (IFIM), the physical habitat method, the weighted effective width method, and the minimum demand method for a biological space; and (4) holistic methods, including the building block method and benchmarking.…”