Towards a more comprehensive assessment of river corridor conditions: A comparison between the Morphological Quality Index and three biotic indices

Abstract

River management and planning of restoration actions require a detailed analysis of stream conditions. However, most biotic and hydromorphological indices that have been developed for implementing the European Water Framework Directive (WFD) are characterized by limited spatial and temporal scales of application. In addition, the indices based on the biological quality elements defined by the WFD are sensitive to water quality but not to hydromorphological alterations. To overcome these limitations, alternative hydromorphological and biotic indices have recently been developed.In this study we compared the results obtained with the Morphological Quality Index (MQI) to those of three biotic indices, the Odonate River Index (ORI) and two BQE-based indices, in seven rivers of northern Italy. MQI and ORI resulted highly and significantly correlated, and alterations of river functionality and continuity were the most relevant impacts affecting dragonfly assemblages. Conversely, no significant relationships were found between the MQI and both BQE-based indices and assemblages. The significant correlation between MQI and ORI can be explained by the correspondence of the spatial scale of application (i.e. the whole river corridor). In contrast, the lack of correlation between the BQE-based indices and MQI can probably be attributed to the different spatial scales at which the indices work.The results of this study underline the importance of evaluating the lateral dimension of the river corridor and the need to apply reach-scale indices to achieve a comprehensive evaluation of river corridor conditions and to define appropriate management actions.