Abstract
After a few decades of efforts to detect, quantify and counteract the effects of water pollution on river biota, recent years have brought an increasing understanding of the significance of hydromorphological quality of rivers for their ecological status, and research on Polish Carpathian rivers has contributed to the progress in this field. Our team developed a method of hydromorphological assessment of rivers, which is based on the European Standard EN-14614 and compromises between the needs for practical application and the environmental significance of results. Application of the method in rivers with different channel patterns confirmed its usefulness and showed a significant impact of channelization and channel incision on the hydromorphological quality of Carpathian rivers. Both disturbances simplified flow pattern and homogenised physical habitat conditions in rivers, and the changes are clearly reflected in the reduced abundance and diversity of fish fauna as well as the reduced taxonomic diversity of benthic invertebrate communities. Significant relationships between these biotic characteristics of Polish Carpathian rivers on one hand and the variation of physical habitat conditions and hydromorphological quality of the rivers on the other indicate that recovery of the degraded communities requires such restoration measures that will increase morphological complexity of the watercourses. Environmental changes that took place in Carpathian catchments during the twentieth century have changed water and sediment fluxes in the rivers and thus make it impossible to use the historical state of the watercourses as reference for their restoration. Therefore, reference conditions should be defined as those which exist or would exist under present environmental conditions in the catchment but with the lacking human influence on the channel, riparian zone and floodplain of the river which is to be restored. An erodible corridor seems to be a restoration measure enabling the most effective adjustment of a degraded river to its contemporary regime as well as re-establishment of geomorphic dynamic equilibrium conditions and improvement of hydromorphological conditions for river biota
Highlights
During recent historical times, various pressures related to human activities in catchments and river valleys have resulted in substantial impact on mountain watercourses, with harmful effects on the condition of their ecosystems
A number of aspects concerning the relations between the condition of biotic components of river ecosystems and physical habitat integrity need to be recognised to enable identification of the causes of degradation of the ecological status of particular rivers and formulate appropriate restoration measures (Vaughan et al, 2009; Rinaldi et al, 2013), and research on Polish Carpathian rivers has contributed to the progress in this field
This paper focuses on: development of a practical and environmentally significant method of hydromorphological assessment of rivers the impact of human disturbances on hydromorphological quality of Carpathian rivers and their reflection in the condition of river biocoenoses the mode of defining hydromorphological reference conditions for river restoration identification and implementation of restoration measures highly effective in improving the hydromorphological integrity of piedmont and mountain rivers
Summary
Various pressures related to human activities in catchments and river valleys have resulted in substantial impact on mountain watercourses, with harmful effects on the condition of their ecosystems. Degradation of water quality resulting from increasing delivery of biogenic and chemical pollutants was first recognised as an important cause of declining ecological integrity of river ecosystems This has stimulated substantial efforts to detect, quantify and counteract the effects of water pollution on river biota, and currently water quality in many mountain rivers in densely populated areas is better than it was still a few decades ago. A number of aspects concerning the relations between the condition of biotic components of river ecosystems and physical habitat integrity need to be recognised to enable identification of the causes of degradation of the ecological status of particular rivers and formulate appropriate restoration measures (Vaughan et al, 2009; Rinaldi et al, 2013), and research on Polish Carpathian rivers has contributed to the progress in this field. This paper focuses on: development of a practical and environmentally significant method of hydromorphological assessment of rivers the impact of human disturbances on hydromorphological quality of Carpathian rivers and their reflection in the condition of river biocoenoses the mode of defining hydromorphological reference conditions for river restoration identification and implementation of restoration measures highly effective in improving the hydromorphological integrity of piedmont and mountain rivers
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