Linking Drought Indicators to Policy Actions in the Tagus Basin Drought Management Plan Luis Garrote & Francisco Martin-Carrasco & Francisco Flores-Montoya & Ana Iglesias Received: 30 January 2006 / Accepted: 31 August 2006 / Published online: 8 December 2006 # Springer Science + Business Media B.V. 2006 Abstract One crucial aspect of drought management plans is to establish a link between basin drought state and management actions. Basin state is described by a drought indicator system that includes variables like precipitation, streamflow, reservoir inflow, reservoir storage and groundwater piezometric levels. Basin policy consists on a catalogue of management actions, ranging from enforcing demand reduction strategies to establishing priority of users to allocate scarce water or approving emergency works. In this paper, the methodology applied in the Tagus Basin Drought Management Plan to link operational drought indicators to policy actions in regulated water supply systems is presented. The methodology is based on the evaluation of the probability of not being able to satisfy system demands for a given time horizon. A simplified model of every water resources system in the basin was built to evaluate the threshold of reservoir volume that is required to overcome the drought situation without deficit. For each reservoir level, a set of policy actions is proposed with the goal of guaranteeing essential demands during drought con- ditions. The methodology was validated with a simulation of system behavior for 60 years of historic streamflow series, finding acceptable results in most systems. Key words drought management . drought indicators . water resources . water resources systems . Tagus river Water Resour Manage (2007) 21:873–882 DOI 10.1007/s11269-006-9086-3 L. Garrote (*) : F. Martin-Carrasco Department of Civil Engineering: Hydraulics and Energetics, Universidad Politécnica de Madrid, ETSI Caminos. c/ Prof. Aranguren s/n 28040 Madrid, Spain e-mail: garrote@caminos.upm.es F. Martin-Carrasco e-mail: fmarcar@ciccp.es F. Flores-Montoya Public Works Council, Ministerio de Fomento, c/ Fruela, 8 28011 Madrid, Spain e-mail: fjflores@fomento.es A. Iglesias Department of Agricultural Economics and Social Sciences, Universidad Politécnica de Madrid, Av. Complutense s/n, 28040 Madrid, Spain