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[1] We present a computable general equilibrium model (CGE) for the Balearic Islands, specifically performed to analyze the welfare gains associated with an improvement in the allocation of water rights through voluntary water exchanges (mainly between the agriculture and urban sectors). For the implementation of the empirical model we built the social accounting matrix (SAM) from the last available input-output table of the islands (for the year 1997). Water exchanges provide an important alternative to make the allocation of water flexible enough to cope with the cyclical droughts that characterize the natural water regime on the islands. The main conclusion is that the increased efficiency provided by ''water markets'' makes this option more advantageous than the popular alternative of building new desalinization plants. Contrary to common opinion, a ''water market'' can also have positive and significant impacts on the agricultural income.

Gibbins, C. N., Vericat, D., Batalla, R. J., Gomez, C. M. (2007). Shaking and moving: low rates of sediment transport trigger mass drift of stream invertebrates. Canadian Journal of Fisheries and Aquatic Sciences, 64, 1-5.During floods, river invertebrates may be swept downstream in large numbers. This so-called 'catastrophic drift' leads to a major redistribution of animals, as well as reduced fitness and increased mortality among drifters. We present the first field evidence of the role of sediment movement in triggering catastrophic drift. Experiments indicate that the loss of invertebrates from the bed becomes exponential when shear stress reaches the threshold that entrains bedload. However, we found that low rates of bedload are sufficient to rapidly denude patches of riverbed of their invertebrates and so trigger mass drift. Such low bedload rates occur during small floods. As small floods occur frequently, our results suggest that episodes of catastrophic drift are frequent. This conclusion is counterintuitive, as the persistence of invertebrate communities on riverbeds suggests that such events cannot be truly catastrophic. Moreover, the drift losses that we observed occurred in the absence of significant geomorphic disturbance; this is inconsistent with the notion of catastrophic drift being a response to hydrological disturbance events. We argue that a new definition of catastrophic drift is needed, a definition based not on drift magnitude or the triggering role of sediment movement, but on the population consequences of downstream displacement.Peer reviewe

The authors build a bridge between traditional analysis of the evolution of tourism destinations and economic growth theory. With this aim, they develop an environmental growth model for an economy specializing in tourism and derive the pattern of tourism development with numerical calculations. The results do not contradict the pattern of evolution implied in the tourism area life cycle hypothesis, with environmental deterioration and public goods congestion being the main reasons for the stagnation of the tourism destination. The authors also show the importance of the quality of private tourism services in the evolution of a tourism destination.

This paper develops a general preference model to explain farmers' decisions. Contrary to better known and most commonly used simulation models, the one presented in this paper allows to calibrate, simulate and explain farmers' decisions without assuming linear preferences (as in many multi criteria decision models) or unobservable implicit cost functions (as in positive mathematical programming models). The model is calibrated for crop decisions in the Genil Cabra irrigated area in the Guadalquivir valley (South Spain) as the resulting empirical model is used to study how farmers react by adjusting these decisions when efficiency in the use of water is improved under different scenarios regarding water use rights. The main conclusion of the paper is that the potential water savings from enhancing irrigation technique (636 m 3 ha -1 ) are overcome by increasing water demand due to higher per drop water productivity when sunflower is replaced by maize. For that reason water price increases and/or reduction of water use rights is a necessary condition to convert water savings through improved efficiency into lower water use and better conserved water sources.Additional key words: agricultural policy; mathematical programming; water demand for irrigation. ResumenEvaluación de la mejora de la eficiencia del regadío utilizando un modelo de revelación de preferencias El artículo presenta un modelo de revelación de preferencias que permite explicar las decisiones de cultivo de los regantes. Al contrario de los modelos de simulación más conocidos y utilizados, el que se presenta en este trabajo no exige asumir preferencias lineales (como en el caso de las técnicas multicriterio) ni acude a funciones inobservables de costes implícitos (como en los modelos de programación matemática positiva). El modelo propuesto se calibra para la comarca agraria del Genil Cabra en el valle del Guadalquivir (sur de España) y el modelo empírico resultante se utiliza para estudiar las reacciones de los agricultores a las mejoras en la técnica de riego bajo distintos contextos de derechos de propiedad. La principal conclusión del trabajo es que los ahorros potenciales de agua que se consiguen con la mejora técnica del sistema de riego (636 m 3 ha -1 ) son compensados por los aumentos de la demanda derivados de la mayor productividad del agua cuando el girasol es sustituido por maíz. Por este motivo, para conseguir una reducción efectiva del uso del agua y, por tanto, una mejora en las fuentes del recurso, es necesario aumentar los precios y/o reducir la cantidad de derechos de propiedad.Palabras clave adicionales: demanda de agua