• Bassam Kattaa

      Articles written in Journal of Earth System Science

    • Investigation of hydrological drought using Cumulative Standardized Precipitation Index (SPI 30) in the eastern Mediterranean region (Damascus, Syria)

      Boulos Abou Zakhem Bassam Kattaa

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      The Eastern Mediterranean region has been exposed to drought episodes, which have been occurring morefrequently during the last decades. The objective of the present paper is to study the precipitation regimeof the Damascus (Mazzeh) meteoric station by analysing drought characteristics using the StandardizedPrecipitation Index (SPI) and comparing this with the drought in Cyprus. The cumulative droughtconcept is proposed to characterize long-term hydrologic drought, which affects the shallow groundwaterproductivity in terms of quantity and quality. Gamma probability distribution was fitted to the long-termannual precipitation in Damascus from 1918–1919 to 2007–2008 (n = 90 years). Generally, a decreasingtrend of 17% to the mean annual rainfall of Damascus and 13% to the mean annual rainfall of Cypruswas estimated between 1970 and 2000. The SPI identifies three major extended drought periods: (1)9 years of severe drought (1954–1963) with an average 20% precipitation deficit per year compared tothe mean. (2) 8 years of severe drought (1983–1991) with a 27% deficit per year on average. (3) 9 yearsof extreme drought (1993–2002) with a 31% deficit per year on average. The cumulative standardizedprecipitation index (SPI 30) demonstrates positive values for the first period and is indicative of havingno effect on the global water balance. SPI 30 exhibits sensitive equilibrium with near zero values / a nearzero value (±1.5) for the second period. For the third period, however, the SPI 30 decreases below −10indicating an extreme hydrological drought that has negative consequences on the recent groundwaterrecharge. It is required to develop and implement a sustainable groundwater management strategy toreduce long-terms drought risks. Generally, the SPI 30 in Cyprus is parallel to that in Damascus witha 3–5 year delay. Thus, the central zone of the Eastern Mediterranean region is facing big challengesand has been suffering from three decades of moderate to severe hydrological drought (SPI 30 = −5to −10) causing a severe decrease in springs discharges of the region. Therefore, in order to reduce theclimate change effects on water resources, it is necessary to adopt a sustainable proactive managementplan during the frequent severe droughts.

    • Overexploitation and cumulative drought trend effect on Ras El Ain karstic spring discharge (Khabour Sub-basin, Syria)

      Boulos Abou Zakhem Bassam Kattaa

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      The effects of climate change and overexploitation are being strongly perceived in the studied area and the springs discharge is obviously affected. In this paper, Ras El Ain spring discharge and precipitation were analyzed by normalized methods on an yearly timescale. The deficit of Ras El Ain spring discharge due to overexploitation factors and drought effects was estimated. Cumulative drought analyses were carried out using SPI10 and SQI10. Finally, the decreasing trends of the spring discharge due to the deficiency in rainfall were analyzed. The main results reveal that the annual mean deficit of Ras El Ain spring discharge due to overpumping was between 32 and 45%, whereas, annual mean deficit related to drought was between 22 and 35% on average, during the last 30 years (post-1984). The moving averages of SPI and SQI delineate very well the drought periods during last three decades. The cumulative droughts using SPI10 and SQI10 reveal that wet period (pre-1984) with positive values was characterized by high precipitation and spring discharge. Overexploitation period (1984–1989) is distinguished by decreasing SQI10 values whereas, SPI10 is almost stable. The response of the karst system to the precipitation signal has been changed, during the drought period (1990–2000), and the spring behaviour has been modified due to the first overexploitation period. Finally, overexploitation period (2001–2008) is related to the second phase of groundwater intensive pumping for irrigation purposes. Consequently, this period is completely catastrophic causing the drying up of the spring. The decreasing trends analyzed using DPI and DQI showed annual decreasing rates relative to the mean values of −0.268% and −0.105%, respectively. Thus, the results of theoretical model reveal that precipitation will decrease by about DPI=−20.7% and the discharge will decline by about −9.2% by 2050. Consequently, the declining discharge due to climatic variation under natural conditions as pre-1984 was about 10%. Whereas, the catastrophic drying up of the spring was probably the consequence of the anthropogenic effects. Accordingly, it requires the development of sustainable water resources management program to reduce long-term drought risks, restore the groundwater reservoir and minimize the overexploitation effects on spring discharge.

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