Drought vulnerability assessment and potential adaptation options in the Aegean islands

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1 Drought vulnerability assessment and potential adaptation options in the Aegean islands P. M. Stathatou & E. Kampragou School of Chemical Engineering, National Technical University of Athens, Zografou, Athens, Greece ABSTRACT: Drought events of increasing frequency, duration and intensity are expected to seriously affect the Mediterranean region in the following decades, and particularly its arid insular areas. In the Greek islands of the Aegean Archipelago, which are highly vulnerable to drought due to their specific natural, physical, and socio-economic conditions, significant water deficits are expected, which are likely to cause severe impacts on local economy and society. This paper aims to assess the drought vulnerability of the Aegean islands and to identify the potential contribution of supply enhancement options in vulnerability reduction. The proposed methodology is applied in the islands of Syros, Milos and Naxos, which were selected for their diverse water systems, combined with high population and tourism development. Proxy indicators were used to identify the underlying drought vulnerability factors, while an overall vulnerability index was estimated, to assess the anticipated contribution of water reuse options to drought vulnerability reduction. 1 INTRODUCTION Drought hazard is receiving growing attention in central and Southern Europe, as drought events are becoming more acute, and are anticipated to increase in frequency, duration and intensity in the coming years (IPCC 2014). To that end, drought risk management, and drought vulnerability analysis in particular, emerges as a critical component of water policy, allowing for the identification of vulnerable groups and sectors, enhancing preparedness and responses for alleviating drought impacts and building resilience of societies (UNISDR 2009). The Mediterranean region is one of the most often drought-stricken regions of Europe, confronted with adverse economic and social impacts (Iglesias et al. 2007). The islands of the Aegean Archipelago, located in the Northeastern Mediterranean region, are highly vulnerable to drought (Karavitis et al. 2011), and face significant water deficits, due to their specific natural (isolated location, geographic fragmentation, high temporal variation of rainfall), physical (limited storage capacity and great dependency on groundwater sources), and socio-economic (irrigated agriculture and tourism are the main sources of income) conditions. Currently applied water management practices (mainly water transfers from the mainland, and inadequate or non-operative desalination plants) have failed to deliver a sustainable solution towards adverse water related conditions ( Integration of treated wastewater reuse into water resources management plans for the area is a significant issue, as it can provide a reliable alternative water source addressing both water demand and supply (Raso 2013, Gikas & Tchobanoglous 2009) The aim of this paper is to assess the drought vulnerability of the Aegean islands and to identify the potential contribution of different adaptation options in vulnerability reduction, focusing on the reuse of treated wastewater. A comprehensive methodological framework is adopted for the vulnerability assessment, expressing natural, physical, socio-economic and institutional attributes of the examined areas. The proposed methodology is applied in the islands of Syros, Milos and

2 Naxos in Cyclades complex, Greece, which were selected because of their negative water balance, high population and tourism development. Proxy indicators are used to identify the underlying drought vulnerability factors, forming an overall vulnerability index (VI). The anticipated contribution of wastewater reuse options to drought vulnerability reduction is assessed using the VI. 2 METHODOLOGY 2.1 Drought vulnerability definition and assessment framework There are more than one definitions of drought vulnerability. In this paper, vulnerability is defined according to the European Environmental Agency, as the degree to which a system is susceptible to, and unable to cope with, injury, damage, or harm. Vulnerability is linked to the potential impacts due to drought events and is being used to assess the susceptibility of socio-economic systems to drought (Wilhelmi & Wilhite 2002). Exposure, sensitivity and adaptive capacity are considered the three aspects of vulnerability (IPCC 2001, Gallopín 2006). The exposure (EXP) and sensitivity (SENS) aspects are considered to be positively associated with vulnerability, expressing the potential drought impacts on the analyzed system, while the adaptive capacity (AC) aspect is considered to be negatively associated with vulnerability, expressing the potential of the system to cope with drought impacts and risks. Therefore, drought vulnerability can be expressed as: V f ( EXP SENS AC) (1) Several methodological approaches exist for analyzing and quantifying vulnerability (e.g. Alcamo et al. 2008, Fontaine & Steinemann 2009, Liu et al. 2013). Indicator-based frameworks are the most widely used, expressing vulnerability through sets of proxy indicators or composite indices (Stathatou et al. 2014). Such a framework was adopted in the present work, and a composite index (VI) was estimated to assess drought vulnerability, following five steps: Step 1: a set of 15 proxy indicators were selected. The selected indicators reflect the local context of the analyzed areas and provide insight on the frequency and duration of drought events, the drought impacts and the prevailing socio-economic conditions related to water use. Indicators related to wastewater reuse were also included, to examine the potential contribution of this option to vulnerability reduction. Data availability and avoidance of overlapping were the main criteria for indicator selection. Each one of the selected indicators falls under a vulnerability aspect: o EXP: drought intensity DI (sum of monthly SPI-12, for the year 2007), drought frequency DF (frequency of extreme events based on SPI-12, comparison of and ), water availability per capita / Falkenmark indicator FI (m 3 / capita / yr), wastewater discharged untreated as percentage of available water recourses UWW (%); o SENS: population density PD (inhabitants / km 2 ), demand coverage of domestic water use DC (%), demand coverage of irrigation water use IC (%), tourism intensity TI (number of beds / capita), groundwater quality GQ (qualitative score); o AC: access to information during drought periods AI (qualitative score), water conflicts WC (%), water supply with reclaimed water WR (%), losses in water supply networks WL (%), drought governance & management frameworks DG (qualitative score), legal & institutional frameworks related to wastewater reuse LIF (qualitative score); Step 2: threshold values were defined for all the selected indicators, to express the contribution of each indicator to vulnerability. The critical values of some indicators, which have already been proposed in the literature, and the mean values for the entire Aegean islands region, were considered thresholds. Step 3: indicator values were normalized as ratios of their respective thresholds. After normalization, threshold values were equal to 1, and indicator values ranged from 0 to 5 (cutoff value). The qualitative indicators were already normalized, as their values were based on expert judgment using a scale from 0 to 5.

3 Step 4: weights were assigned to the selected vulnerability indicators using the Analytical Hierarchy Process (Saaty 1980). The stakeholder views (representatives from the Municipality of Syros-Hermoupolis, the Region of South Aegean, and the Municipal Authority for Water Supply and Sewage of Syros) on the relative importance of the selected indicators were considered for the calculation of weights. Step 5: the VI was estimated as the weighted sum of the vulnerability indicators, based on the adopted vulnerability definition (Eq. 1): VI EX SENS AC w i V i w j V j k. k i j k.. w V (2) where w = weight of the indicator; V = normalized value of the indicator; i = exposure indicator; j= sensitivity indicator; and k= adaptive capacity indicator. The developed VI has a range from -5 (not vulnerable ideal state) to 5 (extremely vulnerable worst state), with 0 standing as the threshold value of the index, suggesting the benchmark above which an area is starting to be vulnerable to drought (critical state). 2.2 The Study Site areas The Aegean islands occupy a total area of 9,104km 2 and have resident population of 508,206 inhabitants (census 2011). Drought events are common, particularly in the Cyclades complex (central part of Aegean Sea), with severe and extreme events accounting for 17% of drought episodes in the period (Tigkas 2008). During the frequent drought periods, the water scarcity problems that the islands face are intensified. The present analysis has been undertaken for three islands of the Cyclades complex (Fig. 1): Syros (SY; 84 km 2 ; 21,507 inh.), Naxos (NA; 427 km 2 ; 20,837 inh.), and Milos (MI; 151 km 2 ; 9932 inh.), which have similar climate and socio-economic contexts, but their environmental conditions vary. Naxos has sufficient internal water resources to satisfy water demand, whereas Syros and Milos face water scarcity. The installation of desalination plants in Syros resolved the problem of water supply for the domestic sector, but water deficits in agriculture remain high. Milos depends mainly on water transfers for meeting water demand (e.g. about 159,800 m 3 were imported in 2004, covering 54 % of total water supply; Karagiannis & Soldatos 2007). Naxos Milos Syros 0% 20% 40% 60% 80% 100% Wet Mild drought Moderate drought Severe drought Extreme drought Figure 1. Location of the islands, and frequency of drought events based on the SPI-12 ( ). 3 RESULTS DISCUSSION 3.1 Drought vulnerability assessment The VI was estimated as the weighted sum of the 15 selected indicators (using Eq. 2):

VI ( 0. 165 DI 0. 165 DF 0. 17 FI 0. 055 UWW ) ( 0. 075 PD 0. 075 DC 0. 13 IC 0. 11 TI 0. 055 GQ ) ( 0. 2 AI 0. 2 WC 0. 15 WR 0. 15 WL 0. 15 DG 0.

The VI for the three analyzed islands: (a) absolute value, (b) the contribution of the three vulnerability aspects (EXP, SENS and AC) to the VI of each island.

4 VI ( DI DF FI UWW ) ( PD DC IC TI GQ ) ( 0. 2 AI 0. 2 WC WR WL DG LIF ) The values of the VI suggest that all three islands are vulnerable to drought (Fig. 2a). (3) Figure 2. The VI for the three analyzed islands: (a) absolute value, (b) the contribution of the three vulnerability aspects (EXP, SENS and AC) to the VI of each island. (VIs were normalized to a range from 0 to 100, using the min-max normalization process, in which the threshold value was set zero). Naxos is the most vulnerable to drought among the three islands, as the extreme drought events of the last 20 years ( ), combined with the intense drought of 2007, have caused significant impacts on water resources availability and allocation (54% uncovered demand for irrigation). Syros, despite not having faced extreme drought events in the recent years, is vulnerable to drought as it struggles with severe water scarcity conditions (annually available freshwater resources per capita are about 385 m³, which is far below the warning threshold of 500 m³ / capita / yr, indicating a main constraint to quality of life; Falkenmark 1989). High population density (212 inhabitants / km 2 in 2011) and economic development in Syros have resulted in severe water shortages (46% in the agricultural and 29% in the domestic sector). Milos is estimated to be the least vulnerable among the three islands. Milos faced an extremely intense drought in 2007, while it was subjected to frequent extreme drought events during the last two decades. Nevertheless, there are no significant water deficits yet, and the available freshwater resources (around 1500 m³ / capita / yr) marginally cover the societal needs. Different combinations of the three vulnerability aspects have formed the VIs of the three islands (Fig. 2b). The contribution of each aspect to the VI is estimated as the difference between the values of each sub-index from the respective composite threshold. Naxos is the most exposed to drought, followed by Milos, while Syros is the least exposed among the three. Syros s sensitivity is high, due to the extremely limited freshwater availability and high population density, while Milos is not sensitive at all. Poor adaptive capacity has a significant contribution in all three islands, mostly due to weak drought management frameworks and limited access to information during drought periods. In addition, the lack of alternative water resources to cope with demand, such as treated wastewater, limits the adaptive capacity of the islands in case of drought. 3.2 Identification of potential drought adaptation options: applications of wastewater reuse The potential contribution of reclaimed water to drought vulnerability reduction was investigated. Naxos and Syros have Wastewater Treatment Plants (WWTP) in operation, while the WWTP of Milos is under construction. The current operation conditions of the existing treatment units in Naxos and Syros, and the intended operation conditions of the planned unit in Milos were considered, to estimate the potentially available quantity and quality of the treated wastewater, which could be used to supply different water uses. Data on the WWTPs were taken from the study of the Hellenic Ministry of Development (HMD 2006). The WWTP which serves Syros provides secondary wastewater treatment, with nitrogen removal and disinfection (chlorination). It could provide about 1,040,250 m 3 of treated wastewater per year. Four WWTPs of tertiary treatment serve the island of Naxos with a cumulative annually

5 potential supply of about 1,297,000 m 3 of treated wastewater (the mean winter influent flows were considered). The planned WWTP in Milos will have the ability to treat up to 500 m 3 / day in winter, thus providing about 173,400 m 3 of tertiary treated wastewater per year. Two alternative potential applications of wastewater reuse were investigated: a) reuse for agricultural irrigation, and b) reuse for supplying municipal water uses, such as irrigation of public open spaces, which account for about 15% of domestic water demand (HMD 2006). Both applications were investigated for Naxos and Milos, while for the island of Syros only agricultural irrigation was considered, as the quality of the treated effluents is not suitable for other uses (JMD /11). Industrial applications of wastewater reuse were not considered, as industrial activity is limited in the islands (HMD 2006). The potential reduction in drought vulnerability that could be achieved through different applications of wastewater reuse in the islands is presented in Table 1, expressed as the percent reduction in the VI. Table 1. Drought vulnerability reduction achieved through different wastewater reuse applications. Island Current Conditions (no reuse) Application A Application B VI VI Reduction VI Reduction Milos % % Naxos % % Syros % - - As shown in Table 1, the reuse of treated wastewater for crop irrigation contributes the most in drought vulnerability reduction. In the islands of Milos and Syros the agricultural water deficits could be completely covered, also providing a surplus of 148,000 m 3 and 170,000 m 3 respectively that could be used to cover domestic water demand. In the case of Naxos, although wastewater reuse for municipal water uses could completely cover the domestic water deficit, reuse for crop irrigation seems to have a greater contribution in vulnerability reduction, as the amount of supplied water increases. 4 CONCLUSIONS The developed VI provided great insight on the factors that shape drought vulnerability in the examined islands. Extreme drought events further aggravated the already limited freshwater availability, resulting in water deficits and allocation issues. The tourism-driven economic development, combined with an insufficient drought management framework, renders the islands vulnerable to drought, to smaller (Milos) or greater extent (Naxos). Wastewater reuse for crop irrigation could be an effective drought adaptation option, eliminating the agricultural deficits in most cases, and alleviating water scarcity conditions reserving high quality water for other uses. Additionally, in islands without WWTPs, such as Milos, the installation of treatment facilities could enhance adaptation to drought. Further research is needed, however, to assess the actual contribution of the identified options to drought vulnerability reduction, as the infrastructure and cost requirements, and the environmental and social impacts of these options were not considered in the current analysis. Moreover, the matching of demand and supply seasonality is a significant factor that should be considered in case of agricultural reuse. The proposed methodological framework provides estimation and facilitates the comparison of the drought vulnerability of the Aegean islands, and can be a useful tool to assess and identify potential drought adaptation options. The selected vulnerability indicators and the adopted weighting scheme, which is based on expert judgment, express the local needs and priorities related to water use (e.g. tourism intensity). Nonetheless, the framework can be applied in all areas, by selecting the proper set of vulnerability indicators and adjusting their weights accordingly, to express the prevailing conditions. In addition, the VI can be used to rank areas with respect to their vulnerability threshold, and assess alternative drought adaptation options. The assessment results can provide useful input concerning the underlying factors of drought vulnerability, and can support water resources management and planning processes in identifying suitable interventions for vulnerability reduction.

6 5 ACKNOWLEDGMENTS The research leading to these results has received funding from the European Union (EU) Seventh Framework Programme (FP7/ ) under Grant Agreement No : Project DROUGHT-R&SPI Fostering European Drought Research and Science-Policy Interfacing. The results presented in this paper reflect only the authors views and the EU is not liable for any use that may be made of the information contained therein. REFERENCES Alcamo, J., Acosta-Michlik, L., Carius, A., Eierdanz, F., Klein, R.J.T., Kromker, D. & Taenzler, D A new approach to quantifying and comparing vulnerability to drought. Regional Environmental Change 8: European Environment Agency (EEA): Environmental Terminology and Discovery Service (ETDS): Accessed 7 February Falkenmark, M The massive water scarcity now threatening Africa-why isn't it being addressed?, Ambio 18: Fontaine, M.M. & Steinemann, A.C Assessing Vulnerability to Natural Hazards: Impact-Based Method and Application to Drought in Washington State. Natural Hazards Review 10(1): Gallopín, G.C Linkages between vulnerability, resilience, and adaptive capacity. Global Environmental Change 16: Gikas, P. & Tchobanoglous, G Sustainable use of water in the Aegean Islands. Journal of Environmental Management 90: Hellenic Ministry of Development Development of Systems and Tools for Water Resources Management in the Hydrological Department of the Aegean Islands. Iglesias, A., Garrote, L., Flores, F. & Moneo, M Challenges to Manage the Risk of Water Scarcity and Climate Change in the Mediterranean. Water Resources Management 21: IPCC Climate Change 2001: Synthesis Report. A Contribution of Working Groups I, II and III to the Third Assessment Report of the Intergovernmental Panel on Climate Change [R.T. Watson and the Core Writing Team (eds.)]. Cambridge and New York: Cambridge University Press. IPCC Climate Change 2014: Impacts, Adaptation, and Vulnerability, Part B: Regional Aspects, Chapter 23:Europe.[V.R. Barros, C.B. Field, D.J. Dokken, M.D. Mastrandrea, K.J. Mach, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, & L.L. White (eds)]. Cambridge and New York: Cambridge University. Joint Ministerial Decision / Settlement of measures, conditions and procedures for the waste water reuse and other clauses. Greek Government Gazette Β 354/ Karagiannis, I.C. & Soldatos, P.G Current status of water desalination in the Aegean Islands. Desalination 203: Karavitis, C.A., Alexandris, S., Tsesmelis, D.E. & Athanasopoulos, G Application of the Standardized Precipitation Index (SPI) in Greece. Water 3: Liu, X., Wang, Y., Peng, J., Braimoh, A.K. & Yin, H Assessing vulnerability to drought based on exposure, sensitivity and adaptive capacity: A case study in middle Inner Mongolia of China. Chinese Geographical Science 23(1): Raso, J Updated report on wastewater reuse in the European Union. TYPSA Consulting engineers & architects. Saaty, T.L The Analytic Hierarchy Process. New York: McGraw- Hill International. Stathatou, P.M., Kampragou, E., Grigoropoulou, G., Assimacopoulos, D., Karavitis, C., Porto, M.F.A., Gironás, J., Vanegas, M. & Reyna, S Vulnerability of water systems: A comprehensive framework for its assessment and identification of adaptation strategies. Proc. ADAPTtoCLIMATE Intern. Conf., Nicosia, March Tigkas, D Drought Characterization and Monitoring in Regions of Greece. European Water 23/24: UNISDR Drought Risk Reduction Framework and Practices: Contributing to the Implementation of the Hyogo Framework for Action. Geneva: United Nations secretariat of the International Strategy for Disaster Reduction (UNISDR). Wilhelmi, O.V. & Wilhite, D.A Assessing vulnerability to agricultural drought: A Nebraska case study. Natural Hazards 25:

TREATED WASTEWATER REUSE POTENTIAL: MITIGATING WATER SCARCITY PROBLEMS IN THE AEGEAN ISLANDS

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