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Congress: 2008
Author(s): Irene Blanco, Consuelo Varela-Ortega, Guillermo Flichman
Consuelo Varela- Ortega is professor at the Polytechnic University of Madrid, Madrid, Spain. Address: Departamento de economía y ciencias sociales agrarias. ETSI Agrónomos. Avda. Ciudad universitaria s/n. 28040, Madrid, Spain. Tel.: (+34) 91 336 57 90; Fax

Keyword(s): Irrigation, groundwater management, ecosystem conservation, mathematical programming model, water policies, impact assessment.
AbstractGroundwater in Spain, as in other arid or semiarid countries worldwide, has been intensely used for the expansion of irrigated agriculture. This booming development has induced a remarkable socioeconomic development in many rural areas. However, in many cases, the largely uncontrolled use of groundwater resources has produced far-reaching environmental problems. One remarkable example of overexploitation of groundwater resources can be found in the Spanish Western La Mancha Aquifer. The excessive, and sometimes illegal, water abstraction for irrigation agriculture has resulted in the Aquifer’s overexploitation and has been responsible of the degradation of the associated wetlands of the national park “Tablas de Daimiel”, an internationally reputed, Ramsar -nominated aquatic ecosystem of high ecological value. The aim of this paper is to propose and analyze alternative water conservation policies that will attain a reduction in water consumption, compatible with the natural recharge rate of the Western La Mancha aquifer that will, ultimately, promote a sustainable groundwater management in the Upper Guadiana basin. To undertake this analysis, an aggregated non-linear Mathematical Programming Model of constrained optimization has been built to simulate farmers’ behaviour confronted to different policy scenarios (stakeholder and policy-driven) under the uncertainty of climate and market variations. The policy simulations are namely the implementation of the on-going national water use quota system, the application of alternative water pricing schemes (uniform volumetric and block-rate water tariffs), and the establishment of a water rights market. In all the simulated scenarios, it has been previously considered that all illegal wells have been legalized beforehand by paying an entry right fee. Results show that controlling illegal water mining is a necessary condition but it is not sufficient to recover the aquifer. This policy option will contribute to reduce conflicts and social unrest among irrigators but will not decrease the volume of water extracted to the optimum desired level. Consequently, other measures will be necessary for an effective water management in this area. Among these, water pricing schemes seem the most cost-effective systems to reach the goal of aquifer sustainability but will entail important income losses that could put at risk the viability of the farms with less flexible cropping patterns. On the contrary, the quota system has the highest social cost but induces lower income losses to the farmers, following the water-rights market. Therefore, we cannot conclude that a unique water conservation policy instrument will be the best overall solution for all types of holdings and farmers that will respond to efficiency as well as to equity considerations. It seems reasonable to make a combination of the proposed tools. Furthermore, the social cost of the different water management schemes analyzed is very similar in an aggregated approach. The choice of a political instrument will require the carrying out of additional studies where other criteria, not considered in this research, should be taken into consideration, such as long term recurrent costs, agreement of users, institutional capacity and the transaction costs related to the implementation of the selected policy measures.
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