International water resources allocation and conflicts: the case of the Euphrates and Tigris

This paper presents a linear programming model that allocates the waters of the Euphrates and Tigris rivers to irrigation, urban consumption, and on-stream hydroelectricity production in the three riparian countries (Turkey, Syria, and Iraq), by maximizing the aggregate net benefits from water uses while accounting for water-conveyance costs. The model represents, in network form, the system made of the two rivers and their various consumption, supply, and transshipment nodes, and accounts for evaporation and return flows. The constraints include water-conservation balances and maximum and minimum water consumption. The model is used to assess the economic consequences of various cooperation and noncooperation strategies that may be adopted by the riparian countries. Cooperative game-theory concepts (core and Shapley value) are used to identify stable water allocations, under which all three countries find it beneficial to cooperate. The results suggest that an allocation of the total benefits exists, under various scenarios of future energy prices and agricultural productivities, that makes this global cooperation attractive to all countries. Various research extensions are outlined. DOI:10.1068/a3670 ô Author for correspondence. Scheumann (1998). Data on regional development, including the structure of GAP, can be found in Robins (1991), Kolars (1994), and CIA (http://www.odci.gov/cia/publications/ factbook/index.html). The E ^T hydrology (river flows and structure, catchment areas, etc) is described in Naff and Matson (1984), Kolars and Mitchell (1991), Kolars (1992; 1994), Kliot (1994), and Altinbilek (1997). For more details, see Kucukmehmetoglu (2002). Although the above literature provides much of the empirical background of this research, it is essentially qualitative, and does not offer any quantitative modeling framework. The methodology of this research is inspired by the second strand of literature, focusing on (1) water-allocation models, cast as linear and nonlinear optimization models, and (2) cost ^ benefit allocation models, using concepts and techniques of cooperative game theory. Water-allocation models maximize the net benefits derived from various water uses, including irrigation, municipal and industrial consumption, and hydroelectricity production, net of water conveyance and treatment costs. These models generally involve price-sensitive demands and, therefore, their objective functions are cast as total net consumer and producer surpluses. In addition to water quantity allocations, these models provide price equilibrium under different scenarios. Flinn and Guise (1970) develop an interregional price equilibrium model taking the form of a quadratic program, because of linear demand and cost functions. The constraints include both maximum reservoir supply and conveyance capacity limits. The model is applied to a hypothetical river system, and incorporates seasonal variations in demand. Vaux and Howitt (1984) apply a similar model to California, using nonlinear demand functions, and price-sensitive linear supply functions. The results show that market-based water transfers reduce the need for supply-augmenting facilities, and generate welfare gains. Booker and Young (1994) model intrastate and interstate water transfers within the Colorado basin, accounting for both water quantity and quality (salinity) balances. They use an explicit representation of the river twenty-node network, with its tributary inflows, diversion points, reservoirs, and hydropower plants. The model (CRIMö Colorado River Institutional Model) is a nonlinear program that maximizes total net benefits, subject to linear water balance and nonlinear salinity balance constraints. Flows and salinity concentrations are functions of withdrawals, exports, and salt discharges, which are all decision variables. The Colorado is treated as a closed system, with a constant water supply. Model results suggest that efficiency gains are derived primarily from intrastate (not interstate) trade. Becker (1995) formulates a linear program for the optimal allocation of water to Israeli regional crops, where the constraints include maximum reservoir supplies, upper limits on regional agricultural areas and total crop land across all regions, and maximum regional water allocations. The objective function represents the aggregate value added of water over all crops and regions, net of transfer costs. Mahan et al (2002), drawing on Booker and Young (1994), develop a nonlinear net benefit maximization model applied to Southern Alberta. The demand sector includes urban, irrigation, industrial, and hydropower nodes. A novel environmental feature is the explicit account of the conversion of untreated water to treated potable water. Models combining water-system optimization and game theory concepts have been pioneered by Rogers (1969), who formulates a linear program to derive an optimal multipurpose development for the Ganges ^Brahmaputra basin that straddles India and Bangladesh. This model accounts for the complex interactions between hydropower, irrigation, flood control, navigation, and salinity control. The model maximizes the benefits from hydropower production and from irrigation with both diverted river water and pumped groundwater, net of reservoir (storage), tube well field, and embankment 784 M Kucukmehmetoglu, J-M Guldmann