Evaluation of environmental flow assessment methods through combined use of hydrological, hydraulic and biotic parameters

Recognizing the benefits of meso-scale analysis and, subsequently, the fundamental importance of mesohabitats / hydromorphological units (HMU) in the study of ecosystems, a methodological framework is proposed with the primary objective to contribute to the assessment and –possibly– the revision of proposed environmental flows. After processing raster files generated by hydraulic simulation in HEC-RAS in a section of 160 m length of the Upper Acheloos, Hydromorphological Units are classified and mapped by flow depth and speed. The advantage is that the abovementioned parameters are predefined, as opposed to the usual practice of field work, and hydromorphological units are mapped digitally, thus making the process repeatable. An impact assessment on Ionic trout (Salmo farioides; Karaman, 1938) is carried out by comparing HMUs in natural flow regime and in minimum environmental flows -suggested Indicators of Hydrological Alteration (Richter et. al. 1996, 1997) and habitat simulation model (in micro-scale). The output suggests the intensity of environmental impacts on the riverine ecosystem. This approach can be used as a decision support system or as a rudimental mesohabitat simulation model.