Comparative Assessment of Environmental Flow Estimation Methods in a Mediterranean Mountain River

Abstract

The ecological integrity of rivers ultimately depends on flow regime. Flow degradation is especially prominent in Mediterranean systems and assessing environmental flows in modified rivers is difficult, especially in environments with poor hydrologic monitoring and data availability. In many Mediterranean countries, which are characterized by pronounced natural variability and low summer flows, water management actions usually focus on prescribing minimum acceptable flows estimated by hydrologic methods. In this study, a comparative assessment of environmental flow estimation methods is developed in a river with poorly monitored flows and limited understanding of past reference conditions. This assessment incorporates both a hydrologic and a fish habitat simulation effort that takes into consideration hydrologic seasonality in a Greek mountainous river. The results of this study indicate that especially in data scarce regions the utilization of biotic indicators through habitat models, may provide valuable information, beyond that achievable with hydrologic methods, for developing regional environmental flow criteria. Despite the widespread use of the method, challenges in transferability of fish habitat simulation provide undefined levels of uncertainty and may require the concurrent use of different assessment tools and site-specific study.

Comparing environmental flow scenarios from hydrological methods, legislation guidelines, and hydrodynamic habitat models downstream of the Marathon Dam (Attica, Greece)

“…Nearly all hydrological methods applied, including the most popular Tennant method (Tennant, ), calculated lower eflows than the ones required to ensure ecosystem integrity and functionality according to the HHM‐based, ecosystem‐oriented approach followed in our study. Previous comparative studies in various reaches (Nikghalb et al, ; Shokoohi & Amini, ; Stamou et al, ; Theodoropoulos, Vourka, et al, ) showed similar trends (but see Papadaki et al, ); Nikghalb et al () used the habitat preferences of Luciobarbus capito and calculated threefold increased eflows in comparison with those calculated using the Tennant method. Stamou et al () used the habitat preferences of Squalius peloponnensis and calculated eflows two times higher than the hydrology‐based eflows and 10 times higher than those required by the Greek legislation on eflows.…”

“…31, ) supporting the Water Framework Directive 2000/60/EC (European Union Council, ), suggested a three‐tiered hierarchy of the eflow methods' application, depending on the detail/accuracy of the eflow prediction required and on the magnitude of the (possible) hydrological alteration due to the upstream water use (e.g., small‐scale water abstraction or the presence of a large water supply dam). However, eflows have often been calculated using only hydrological methods (e.g., Chen & Weisbrod, ; Efstratiadis, Tegos, Varveris, & Koutsoyiannis, ; Fuladipanah & Jorabloo, ; Ye, Shen, & Chen, ), whereas studies implementing and comparing eflow scenarios based on a combination of different methods in the same study area are limited (Davis & Hirji, ; Li, Cai, Fu, & Liu, ; Nikghalb, Shokoohi, Singh, & Yu, ; Papadaki et al, ; Shokoohi & Amini, ; Stamou et al, ; Tare et al, ).…”

Ecosystem‐based environmental flow assessment in a Greek regulated river with the use of 2D hydrodynamic habitat modelling

“…The low percentage (18%) of European HHMs‐based case studies in the relevant WFD Guidance Document is also indicative of this gap between theoretical research/knowledge and practical application of HHMs. Particularly in Greece, HHMs have only recently been incorporated into EFAs and are currently focused solely on fish (Muñoz‐Mas et al, ; Papadaki et al, ), whereas the legal framework on eflows is still based on simplistic and rather arbitrary hydrological criteria (Ministry of Environment, Energy and Climate Change, ).…”

Comparison of environmental flows from a habitat suitability perspective: A case study in the Naeseong‐cheon Stream in Korea

“…This has led to numerous attempts to compare the environmental flows estimated using different methodologies (Caissie, El-Jabi, & Hebert, 2007;Orth & Leonard, 1990;Papadaki et al, 2017;Shokoohi & Amini, 2014;Theodoropoulos et al, 2018). This has led to numerous attempts to compare the environmental flows estimated using different methodologies (Caissie, El-Jabi, & Hebert, 2007;Orth & Leonard, 1990;Papadaki et al, 2017;Shokoohi & Amini, 2014;Theodoropoulos et al, 2018).…”

“…It is noteworthy that environmental flows change significantly perhaps due to the fact that the methodologies for estimating them are not based on the same fundamental principles. This has led to numerous attempts to compare the environmental flows estimated using different methodologies (Caissie, El-Jabi, & Hebert, 2007;Orth & Leonard, 1990;Papadaki et al, 2017;Shokoohi & Amini, 2014;Theodoropoulos et al, 2018). For example, Orth and Leonard (1990) estimated environmental flows in four reaches of the upper James River basin of Virginia in the United States using the hydrological method and the habitat simulation method.…”