Hydrologic Impacts of Engineering Projects on the Tigris–Euphrates System and Its Marshlands
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Journal of Hydrology (2008) 353,59– 75 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/jhydrol Hydrologic impacts of engineering projects on the Tigris–Euphrates system and its marshlands C. Jones a, M. Sultan a,*, E. Yan b, A. Milewski a, M. Hussein c, A. Al-Dousari d, S. Al-Kaisy e, R. Becker a a Department of Geosciences, Western Michigan University, 1903 West Michigan Avenue, Kalamazoo, MI 49008, USA b Environmental Science Division, Argonne National Laboratory, Chicago, IL, USA c Iraq Reconstruction Management Office, US Embassy, Baghdad, Iraq d Kuwait Institute for Scientific Research, Kuwait City, Kuwait e Department of Applied Geology, University of Tikrit, Tikrit, Iraq Received 25 June 2007; received in revised form 16 January 2008; accepted 22 January 2008 KEYWORDS Summary Rising demands for fresh water supplies are leading to water management Tigris–Euphrates practices that are altering natural flow systems world-wide. One of the most devas- watershed; tated of these natural systems is the Tigris–Euphrates watershed that over the past Continuous rainfall– three decades has witnessed the construction of over 60 engineering projects that elim- runoff model; inated seasonal flooding, reduced natural flow and dramatically reduced the areal SWAT; extent (1966: 8000 km2; 2002: 750 km2) of the Mesopotamian Marshes downstream. Engineering projects We constructed a catchment-based continuous (1964–1998) rainfall runoff model for the watershed (area: 106 km2) using the Soil Water Assessment Tool (SWAT) model to understand the dynamics of the natural flow system, and to investigate the impacts of reduced overall flow and the related land cover and landuse change downstream in the marshes. The model was calibrated (1964–1970) and validated (1971–1998) against stream flow gauge data. Using the calibrated model we calculated the temporal variations in the average monthly flow rate (AMFR), the average monthly peak flow rate (AMPFR), and annual flow volume (AFV) of the Tigris and Euphrates into the marshes at a location near Al-Basrah city (31°N, 47.5°E) throughout the modeled period. Model results indicate that the AMPFR (6301 m3/s) and average annual flow volume (AAFV: 80 · 109 m3/yr) for period A (10/1/1965–09/30/1973), preceding the construction of the major dams is progressively diminished in periods B1 (10/1/1973–09/30/1989; AMP- FR: 3073 m3/s; AAFV: 55 · 109 m3/yr) and B2 (10/1/1989–09/30/1998; AMPFR, 2319 m3/s; AAFV: 50 · 109 m3/yr) that witnessed the construction of the major dams (B1: Keban, Tabqa, Hamrin, Haditha, Mosul, Karakaya; B2: Ataturk) due to the combined effects * Corresponding author. Tel.: +1 269 387 5487. E-mail address: [email protected] (M. Sultan). 0022-1694/$ - see front matter ª 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jhydrol.2008.01.029 60 C. Jones et al. of filling artificial lakes, evaporation and infiltration of impounded water and its utili- zation for irrigation purposes. To investigate the impacts of reduced flow on the areal extent of the marshes, we examined the variation in marsh size extracted from tempo- ral satellite data (1966, 1975, 1976, 1977, 1984, 1985, 1986, 1987) acquired around the same approximate time period (July to September) of the year versus simulated AFV for the period preceding the onset (1987) of major local engineering projects (e.g., Crown of Battles River, Loyalty to the Leader Canal, Mother of Battles River) in and around the investigated marshes. Results indicate that the areal extent of the Central and Al-Hammar marshes (e.g., 1966: 7970 km2, 1977: 6680 km2, 1984: 5270 km2) decreases with a decrease in AFV (e.g., 1966: 60.8 · 109 m3, 1977: 56.9 · 109 m3, 1984: 37.6 · 109 m3). Using a relationship that describes the impact of reduced AFV on the areal extent of the marshes, we evaluated the impact of additional reductions in flow that will result from the implementation of the planned engineering projects on the Tigris–Euphrates system over the next few years. Upon completion of the ongoing South Eastern Anatolia project, with projected reductions in AFV exceeding 5 · 109 m3/yr, the sustainable marshes in the Central and Al-Hammar area will be reduced by at least an additional 550 km2. ª 2008 Elsevier B.V. All rights reserved. Introduction Recently (2002–2007), there has been a reversal in this devastating trend, with the marshland’s area increasing 2 2 Water shortages in the arid parts of the world are affecting from 750 km in 2002–3980 km in 2005 (Jones et al., the human welfare, economic activity, and political stabil- 2005) largely due to piecemeal interventions by locals and ity of these areas. Faced with overpopulation problems the coalition forces. Drainage canals (e.g., COB, LTL, Pros- and demand for development of new agricultural lands to perity River, MOB) were dammed at the inflow point to al- support increasing population, many countries of the arid low the water to continue flowing as it naturally would world are adopting aggressive policies to develop new agri- into the marshes (Basgall, 2003; IMET, 2004). Fig. 2b illus- cultural communities without careful analysis of the envi- trates how a local engineering project, the MOB in this case, ronmental and hydrologic impacts of these projects. can devastate the marshes in a short time and illustrates These problems are exemplified in the countries of the how the revival of the marshes is attainable if these pro- Middle East. Aggressive water management programs by jects were reversed. Similarly, it could be demonstrated Iraq and its neighbors have brought drastic modification that engineering projects, in and around the marsh area, to the Tigris and Euphrates watershed (106 km2) and the had dramatic, but reversible effects on the spatial extent Mesopotamian Marshes downstream in southern Iraq of the marshes. (Fig. 1). The marshlands that extended over an area of In this manuscript, we show that although the major 8000 km2 in the early sixties declined to about 750 km2 in destruction of the marshes could be related to the local the summer of 2002 (Jones et al., 2005). These observed engineering projects in Iraq, it is the reduced flow due to land cover and landuse changes (LCLUC) over the Mesopo- damming in neighboring countries that presents the largest tamian Marshes reflect the impacts of large engineering and more permanent threat to the marshes. The local pro- projects in upstream countries (Turkey, Iran, and Syria) jects were damaging but their devastating impacts could and local engineering projects in Iraq. Examples of up- be readily reverted if the named projects could be elimi- stream projects include the Tabaqa dam (1975; storage nated. The reduced flow due to damming on the other hand capacity (SC): 11.7 · 109 m3) and Tishrine dam (1999; SC: cannot be as easily reverted. 1.9 · 109 m3) in Syria, the Ataturk dam (1992; SC: We constructed a catchment-based continuous (1964– 48.7 · 109 m3) and Keban dam (1975; SC: 31 · 109 m3)in 1998) rainfall–runoff model for the entire watershed and Turkey and the Karkheh dam (2001; SC: 7.8 · 109 m3)in calibrated the model against stream flow data in Turkey Iran (Table 1). Examples of local engineering projects that and in Iraq using the Soil and Water Assessment Tool devastated the marshes include the diversion canals that (SWAT). The calibrated model was used to characterize were largely constructed in the late 1980s and early the natural flow of the system for the time period (1964– 1990s (Jones et al., 2005) to drain the marshes (e.g., Pros- 1970) preceding the construction of the major engineering perity River; Aybas Canal, and Dike; Fig. 2a), or to divert projects and to investigate the hydrologic impacts that re- surface water in and around the marshlands (e.g., Crown sulted from the implementation of the engineering projects of Battles River (COB); Loyalty to the Leader Canal inside and outside of Iraq in the following decades (from (LTL); Mother of Battles River (MOB); Fig. 2a), water that 1970 to 1998). Moreover, the calibrated model was used would have flowed under natural conditions into the as a predictive tool to investigate the impacts of projected marshlands. Fig. 2a also shows the reduction in marshland reductions in river flow with the construction of additional area associated with the implementation of local projects dams in neighboring countries. The SWAT model was se- and large upstream engineering projects between 1969 and lected because (1) the model is an open source code giving 2002. the user the flexibility for making modifications as needed, Hydrologic impacts of engineering projects on the Tigris–Euphrates system and its marshlands 61 Figure 1 Location and extent (dark blue outline) of the Tigris–Euphrates watershed plotted on a color coded digital elevation map derived from Shuttle Radar Topography Mission data (SRTM). Also shown in black contours are the annual precipitation amounts. The lowest annual precipitation (<300 mm) occurs in the Mesopotamian plain and the highest precipitation (>600–1200 mm) falls over the mountainous belt to the north (e.g., Taurus Mountains) and east (Zagros Mountains) of the plains. (2) it is a continuous model, allowing rainfall–runoff and Mountains, across the Mesopotamian plain, into the Central groundwater-recharge estimates to be made over extended and Al-Haweizah marshes, and finally drains in the Arabian periods of time, and (3) Geographic Information System Gulf (Figs. 1 and 2a). The highlands of Turkey provide 88– (GIS) data sets which were generated for the watershed 98% of the Euphrates total flow, modest contributions come could be readily imported into the model. from the Syrian highlands and only minimal additions occur inside the Iraqi borders (UNEP, 2001).