DHRAM: a method for classifying river flow regime alterations for the EC Water Framework Directive

1. A method has been developed for assessing the degree of human alteration of river flow regimes relative to near-natural or reference conditions. 2. The Dundee Hydrological Regime Alteration Method (DHRAM) utilizes the Indicators of Hydrologic Alteration approach of the US Nature Conservancy to classify the risk of damage to in-stream ecology using a five-class scheme compatible with the requirements of the EC Water Framework Directive. 3. Separate methods have been developed for rivers and lakes, though only the former are considered in this paper. 4. DHRAM uses daily mean flow time-series data, representing un-impacted and impacted situations for the site of interest, in relation to any type of anthropogenic hydrological impact such as impoundments, abstractions or flow augmentation. 5. Procedures for coping with different levels of data availability are outlined, utilizing the Micro Low Flows computer package to generate synthetic series of daily mean flows, supplemented by flow alteration data as appropriate. 6. The utility of DHRAM is demonstrated through a pair of Scottish case studies illustrating its ability in classifying regime alteration and supporting mapping, which will be of value to river basin managers. 7. Finally, present and future issues relating to the calibration of DHRAM scores to levels of ecological damage are discussed. Copyright (c) 2005 John Wiley & Sons, Ltd.