Environ Monit Assess (2011) 174:493–508 DOI 10.1007/s10661-010-1473-9 Evaluation of the ecological status of an impaired watershed by using a multi-index approach Liliana Carvalho · Rui Cortes · Adriano A. Bordalo Received: 26 November 2008 / Accepted: 7 April 2010 / Published online: 7 May 2010 © Springer Science+Business Media B.V. 2010 Abstract The objective of this study was to use an integrative approach to assess the ecological sta- tus of a small river impacted by multiple sources of disturbance. The River Febros (NW Portu- gal) is a small and highly impacted non-regulated river; approximately 44% of the watershed area is dedicated to agriculture, but there is also some urbanization. Environmental status was evalu- ated using a new multi-index approach, combin- ing quality indices for water (Water Quality In- dex (WQI)), benthic macroinvertebrates (Iberian Biological Monitoring Working Party Index (IBMWP)), and human modification (Riparian Forest Quality Index (QBR)); Ecological Status River Mediterranean Index (ECOSTRIMED); River Habitat Survey (RHS)). Surveys were car- L. Carvalho (B ) · A. A. Bordalo Laboratory of Hydrobiology, Institute of Biomedical Sciences (ICBAS), University of Porto, Lg. Professor Abel Salazar, 2, 4099-003 Porto, Portugal e-mail: lqacarvalho@gmail.com R. Cortes Florestal Department, University of Trás-os-Montes e Alto Douro (UTAD), Apartado 1013, 5001-911 Vila Real Codex, Portugal A. A. Bordalo CIIMAR/CIMAR – Center for Interdisciplinary Environmental and Marine Research, Rua dos Bragas, 289, 4050-123 Porto, Portugal ried out between October 2002 and 2003, along four stretches of the main course of the river for physicochemical characteristics, as well as wa- ter microbiology and macroinvertebrates. Wa- ter quality was poor at all sites (WQI averaged 30.4%) and decreased downstream. The RHS (as- sessment of instream habitats and the river cor- ridor) and the QBR quantification displayed the same trend. Macroinvertebrates diversity was per- manently low with only the most tolerant insects taxa present; oligochaetes dominated. The ecolog- ical status of River Febros was well represented using the experimental assessment system, where a downstream decrease in condition was notice- able (in spite of a lower water quality upstream). Our results emphasize the importance of assessing several components of disturbed ecosystems in or- der to ascertain overall quality and the importance of promoting improvement of the riparian gallery as a buffer against multiple agents of disturbance. Keywords WQI · IBMWP · RHS · QBR · Scaled values · River Febros Introduction Reliable detection of human impacts on river sys- tems is challenging due to the diversity of bio- logical, chemical, hydrological, and geophysical