Since droughts are natural phenomena, their occurrence cannot be predicted with certainty and thus it must be treated as a random variable. Once drought duration and magnitude have been found objectively, it is possible to plan for the transport of water in known quantities to drought-stricken areas either from alternative water resources or from water stored during wet periods. The summation of deficits over a particular period is referred to as the drought magnitude. Drought intensity is the ratio of drought magnitude to its duration. These drought properties at different truncation levels provide significant hydrological and hydrometeorological design quantities. In this study, the run analysis and z-score are used for determining drought properties of given hydrological series. In addition, kriging is used as a spatial drought analysis for mapping. This study is applied to precipitation records for İstanbul, Edirne, Tekirdağ and Kırklareli in the Trakya region, Turkey and then the drought period, magnitude and standardized precipitation index (SPI) values are presented to depict the relationships between drought duration and magnitude.Key words spatio-temporal drought; duration; deficit; intensity; magnitude; run analysis; SPI Analyse spatio-temporelle des sécheresses dans la région de Trakya, en Turquie Résumé Dans la mesure où les sécheresses sont des phénomènes naturels, leur occurrence ne peut pas être prévue avec certitude et doit donc être considérée comme une variable aléatoire. Une fois que la durée et l'amplitude de la sécheresse ont été évaluées objectivement, il est possible de planifier le transport d'eau, pour des quantités connues, vers les zones victimes de sécheresse depuis des ressources en eau alternatives ou depuis des stocks mobilisés en périodes humides. L'intensité de la sécheresse est le rapport entre l'amplitude de la sécheresse et sa durée. Ces propriétés de la sécheresse, avec différents niveaux critiques, fournissent des grandeurs hydrologiques et hydrométéorologiques significatives pour la planification. Dans cette étude, nous utilisons l'analyse de séquences et le score centré réduit pour déterminer les propriétés des sécheresses de séries hydrologiques données. De plus, nous utilisons le krigeage pour analyser les sécheresses dans l'espace et produire des cartes. Cette étude est une application à des enregistrements de précipitation à Istanbul, Edirne, Tekirdağ et Kırklareli dans la région de Trakya, en Turquie. Nous présentons les périodes de sécheresse et les valeurs d'amplitude et d'indice standardisé de précipitation (ISP) afin de décrire les relations qui existent entre la durée et l'amplitude de la sécheresse.

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Abstract:Drought prediction for in many regions of the world has critical importance for strategic planning agriculture and water management. The occurrence of droughts cannot be predicted with certainty and thus must be treated as random variables. It is the main purpose of this paper to develop a new concept of drought features assessments based on triple drought related hydrometeorological and meteorological variables, namely, rainfall, solar irradiation and sunshine duration. Equal standard rainfall lines are drawn as a map with two reference variables as solar irradiation and sunshine duration. These are referred to as the triple graphical method (TGM) approach. It furnishes rich features of drought behaviour variation based on the rainfall, solar irradiation and sunshine duration. This analysis and the solar irradiation estimation method are applied to seven climatologically different stations in the Republic of Turkey for the monthly data period 1982-1991. The linear relations between drought and the variables of the Angström equation are found between 55% and 94% without Trabzon. Drought and Angström equation parameters are estimated by the proposed methodology. Relations between monthly drought and Angström equation variables are presented by the triple solar-drought graphical method. TGM provides information about the drought occurrences for different combinations of solar irradiation and sunshine duration. TGM graphs help to identify not only precipitation surplus (wet spells) or deficits (dry spells droughts) but also their variations with two more meteorological variables as solar irradiation and sunshine duration.

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