Water Resources Management 6: 249-277, 1992 249 © 1992 Kluwer Academic Publishers. Printed in the Netherlands. Review Article: On Regional Drought Estimation and Analysis G. ROSSI Institute of Hydraulics, Hydrology and Water Management, University of Catania, Italy M. BENEDINI IRSA-CNR, Rome, Italy G. TSAKIRIS and S. GIAKOUMAKIS Department of Rural and Surveying Engineering, National Technical University of A thens, Greece (Received: 16 January 1992; accepted: 28 April 1992) Abstract. The main objective of this paper is to review the existing methodologies for the estimation and analysis of regional drought. As a first step, point drought methods are presented. Further emphasis is given to the definition and estimation of regional drought characteristics. Stochastic processes for simulating the time-space variability of drought, are presented. Finally, illustrative examples are shown and recommendations for further research are given. Key words. Point drought, regional drought, stochastic models, deficit area, low-flow analysis. 1. Introduction The adverse effects of drought on both water supply systems and environment, are expected to increase in the coming years. In fact, even without referring to the controversial matter of climate change on a world scale, water resources present a natural variability from year to year, so that the risk of severe water shortage in all domains of water use becomes greater as the water demand increases. Implementation of adequate measures to control and/or mitigate drought conse- quences is recognized as a major matter challenging researchers and scientists involved in the water resources management. A comprehensive approach for studying drought problems includes, among others, the following topics: (i) identification of meteorological causes and drought forecast; (ii) evaluation of hydrologic drought characteristics at a site and over a region; (iii) analysis of economic, environmental and social effects of drought; (iv) definition of appropriate measures for mitigating and controlling drought effects. Although no analytical literature survey of droughts is attempted here, an outline of the most important philosophies in drought evaluation is given below: (a) Drought definition stage, in which several disciplines recognize the importance