In their effort to balance anthropogenic water demand and ecosystem conservation within a sustainable water resources management framework, water managers and stakeholders need sound scientific guidance. In this study, we applied a two-dimensional hydrodynamic habitat model using benthic macroinvertebrates as the target aquatic community, and carried out an environmental flow (eflow) assessment downstream of the Marathon Reservoir (Attica, central Greece). Hydrology-based eflow scenarios were additionally developed over an 11-year period, and the lowest acceptable ecosystem-based eflow was compared with the hydrology-based environmental flow predictions. We found that the hydrological methods tend to under-estimate the eflows required to ensure functional aquatic ecosystems. The results showed that (i) the different hydrological methods developed highly variable eflow scenarios, ranging from 0.0006 m3/s to 0.18 m3/s, (ii) the ecosystem-based environmental flow was up to 183% higher than the hydrology-based ones and 26% to 465% higher than those defined by the national legislation and (iii) the probability of agreement between hydrological and ecological predictions was 12.5%, as only one out of the eight hydrology-based scenarios coincided with the ecosystem-based eflows. We conclude that hydrological methods should be used with caution in the absence of ecological information. Their use as stand-alone tools seems problematic and bears a high risk of producing inappropriate environmental flow scenarios. Integrative frameworks combining hydrological-ecological methods could be useful to provide information on what is ecologically-acceptable and hydrologically-socially feasible, but since the two methods comprise structurally-different, non-interacting concepts, they are inherently insufficient to increase the confidence of predicting and selecting environmental flows.     «

In their effort to balance anthropogenic water demand and ecosystem conservation within a sustainable water resources management framework, water managers and stakeholders need sound scientific guidance. In this study, we applied a two-dimensional hydrodynamic habitat model using benthic macroinvertebrates as the target aquatic community, and carried out an environmental flow (eflow) assessment downstream of the Marathon Reservoir (Attica, central Greece). Hydrology-based eflow scenarios were ad...     »