Abstract:The main premise of the current effort is that the use of a drought index, such as Standardized Precipitation Index (SPI), may lead to a more appropriate understanding of drought duration, magnitude and spatial extent in semi-arid areas like Greece. The importance of the Index may be marked in its simplicity and its ability to identify the beginning and end of a drought event. Thus, it may point towards drought contingency planning and through it to drought alert mechanisms. In this context, Greece, as it very often faces the hazardous impacts of droughts, presents an almost ideal case for the SPI application. The present approach examines the SPI drought index application for all of Greece and it is evaluated accordingly by historical precipitation data. Different time series of data from 46 precipitation stations, covering the period 1947-2004, and for time scales of 1, 3, 6, 12 and 24 months, were used. The computation of the index was achieved by the appropriate usage of a pertinent software tool. Then, spatial representation of the SPI values was carried out with geo-statistical methods using the SURFER 9 software package. The results underline the potential that the SPI usage exhibits in a drought alert and forecasting effort as part of a drought contingency planning posture.

Drought is a complex natural phenomenon that lacks a universally accepted definition, thus it is difficult to confront holistically. Several efforts have been made towards managing the widespread and catastrophic drought impacts. In this quest, the concept of vulnerability to drought seems to offer some significant potential. In the present attempt, a standardized drought vulnerability index (SDVI) is presented, applied, and spatially visualized through geostatistical methods on a country scale. Greece, experiencing frequent and intense droughts, was selected as the study site. In an effort to link drought characteristics to impacts, the index incorporates water supply information, demand data, the state of the relevant water infrastructure and climatic parameters represented by the standardized precipitation index. The index showed potential in portraying various vulnerability states and followed satisfactorily the vulnerability fluctuations in Greece in relation to recorded drought hazard dimensions and impacts. The SDVI may be considered as a first step for the emergence of an integrated SDVI with multiscalar applications in environmental research and decision-making. It is believed that improving techniques in index formulation may complement more reasonable and acceptable solutions to water challenges posed by droughts and help avoid a drifting sense of continuous 'water crises'.

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Human activities and climate change constitute the contemporary catalyst for natural processes and their impacts, i.e., geo-environmental hazards. Globally, natural catastrophic phenomena and hazards, such as drought, soil erosion, quantitative and qualitative degradation of groundwater, frost, flooding, sea level rise, etc., are intensified by anthropogenic factors. Thus, they present rapid increase in intensity, frequency of occurrence, spatial density, and significant spread of the areas of occurrence. The impact of these phenomena is devastating to human life and to global economies, private holdings, infrastructure, etc., while in a wider context it has a very negative effect on the social, environmental, and economic status of the affected region. Geospatial technologies including Geographic Information Systems, Remote Sensing—Earth Observation as well as related spatial data analysis tools, models, databases, contribute nowadays significantly in predicting, preventing, researching, addressing, rehabilitating, and managing these phenomena and their effects. This review attempts to mark the most devastating geo-hazards from the view of environmental monitoring, covering the state of the art in the use of geospatial technologies in that respect. It also defines the main challenge of this new era which is nothing more than the fictitious exploitation of the information produced by the environmental monitoring so that the necessary policies are taken in the direction of a sustainable future. The review highlights the potential and increasing added value of geographic information as a means to support environmental monitoring in the face of climate change. The growth in geographic information seems to be rapidly accelerated due to the technological and scientific developments that will continue with exponential progress in the years to come. Nonetheless, as it is also highlighted in this review continuous monitoring of the environment is subject to an interdisciplinary approach and contains an amount of actions that cover both the development of natural phenomena and their catastrophic effects mostly due to climate change.

The degradation of natural resources at an intense rate creates serious problems in the environmental systems particularly with the compounding effects of climatic vagaries and changes. On the one hand, desertification is a crucial universal, mostly an anthropogenic environmental issue affecting soils all over the world. On the other hand, drought is a natural phenomenon in direct association with reduced rainfall in various spatial and temporal frames. Vulnerabilities to drought and desertification are complex processes caused by environmental, ecological, social, economic and anthropogenic factors. Particularly for the Mediterranean semi-arid conditions, where the physical and structural systems are more vulnerable, the abuse and overuse of the natural resources lead to their degradation and ultimately, if the current trends continue, to their marginalization. The scope of the current effort is trying to find any common drivers for the pressures of both processes. Thus, the vulnerabilities to drought and desertification are comparing by using the Standardized Drought Vulnerability Index (SDVI) and the Environmentally Sensitive Areas Index (ESAI). The indices are calculated from October 1983 to September 1996 in Greece. Greece is prone to desertification and it is often experiencing intense droughts, thus it presents an almost ideal case study area. The results may indicate that the most important factor for such procedures is the deficits in water resources, either due to lower than usually expected rainfall or to higher societal water demand.