Applicability of the German Hydromorphological Assessment Approach to Tropical Rivers

In addition to water quality, hydromorphological characteristics are crucial for the integrity of river ecosystems: Factors such as flow diversity, substrate variety, or riparian vegetation create diverse habitats for aquatic organisms with their specific demands. These habitats are impaired by channelization, longitudinal river fragmentation, and degradation of the riparian vegetation. In the state of Rio de Janeiro, rivers are exposed to increasing anthropogenic pressures mainly caused by urban growth, intensive agricultural land use, and alterations induced by climate change. While knowledge about the resulting deterioration of the water quality is well established, the knowledge base about consequences for the hydromorphological quality is thinner. Consequently, the hydromorphological potentials and deficits have to be identified and assessed to preserve or revitalize river ecosystems. For this purpose, the applicability of the German on-site method (LAWA-OS) was tested for hydromorphological assessment of streams. This method assesses the hydromorphological state of stream sections against predefined reference conditions. Based on the assessment results, the method identifies stream sections with different ecological development possibilities such as preservation, revitalization, or restriction. This article describes an on-site application test and formulates the applicability of the LAWA-OS method in Brazil by the example of the state of Rio de Janeiro.