This paper evaluates the effectiveness of changing land allocation among crops as a mechanism for increasing social welfare, where production profits and amenity benefits are augmented. A positive mathematical programming model is calibrated and applied to the northern part of Israel, using a crop-discriminating amenity-benefits function. Changes in land allocation increase social welfare by 2.4% nationwide, and by up to 15% on the regional level. Regional scale farming-profit losses amount to up to 6%. Due to the decreasing-return-to-scale nature of the amenity-benefits function, the interregional variability appears sensitive to the manner in which the country is divided into regions.

[1] Blending fresh and saline irrigation waters is implemented in many countries facing water scarcity. However, when analyzed at the field level, previous economic studies have indicated that blending fresh and saline water is suboptimal. This paper examines the blending issue on a regional scale, where both water sources and land are concurrently allocated to crops. Regional water distribution networks that enable salinity adjustment at the field level are compared to networks that allow controlling water salinity on a regional scale only, such that salt concentrations cannot differ by crop. We characterize the conditions for blending to be an optimal strategy under regional salinity control networks, and show that these conditions can be met by an empirical water production model commonly used in the literature. Empirical analysis of 16 regions in Israel revealed optimal blending in six of them. However, regardless of whether blending is optimal or not, the optimal fresh-water application is higher under regional salinity control networks, implying that blending does not support freshwater conservation. The paper analyzes the relationship between water and land constraints' shadow values, and the properties of the two water distribution networks. We show that although farming revenues are higher under networks that allow assignment of specific water salinities to crops, regional salinity control networks can become more profitable to farmers who face prices set endogenously so as to be the binding factor on the use of constrained water and land. The implications of the network selection on intraregional water supply costs are discussed.Citation: Kan, I., and M. Rapaport-Rom (2012), Regional blending of fresh and saline irrigation water: Is it efficient? Water Resour.

Exploitation of alternative water sources is expected to grow in the decades to come in water-stressed countries with fast population growth, especially in regions where a further decline of natural freshwater availability is expected due to climate change. Increasing utilization of non-freshwater usually leads to salinity build-up in fields and water sources as well as accumulation of various pollutants — both having a considerable impact on the suitability of non-freshwater for irrigation due to constraints associated with crop salinity tolerance and food safety regulations. We developed a linked Computable General Equilibrium (CGE) — farm-level model of a water economy with representation for multiple water types characterized by different qualities. We employ the model to assess the impact of water shortage on the Israeli economy, where steadily growing water scarcity leads to an increasing utilization of alternative water sources. We simulate water shortage scenarios based on the Long Term National Master Plan for The Water Economy developed by the Israeli Water Authority (IWA). The linked CGE — farm-level model provides a mechanism for estimating the Constant Elasticity of Substitution (CES) rates between different irrigation water types used in agriculture. This mechanism accounts for the effects of salinity on yields and takes into consideration food safety regulations for irrigating crops with treated wastewater. We demonstrate that, in contrast to previous studies, CES rates between different water types are not identical. The CES rates obtained in our study have relatively low values, which can be attributed to the constraints associated with crop salinity tolerance and food safety regulations. Our results reveal that water shortage can lead to a significant decline of Israel’s GDP, where a considerable part of the decline is attributed to the decrease in agricultural outputs. The magnitude of the impact depends on the underlying assumptions regarding future desalination capacity. To further study the effect of desalination, we run simulations under various desalination levels and examine its impact on the GDP. We also examine the extent to which the impact of water shortage is sensitive to CES rates between different irrigation water types.

This study presents an internal modification of a dynamic computable general equilibrium model, ICES, employing inputs from a partial equilibrium model for the agricultural sector, VALUE. The aim is to quantify and analyze the medium-term socio-economic consequences of projected climate change. The methodology is innovative as it combines state-of-the-art knowledge from economic and biophysical sources and is demonstrated in application to two Mediterrenean countries: Israel and Italy. The information from the VALUE model was incorporated into the ICES economic model to improve the agricultural production structure. The new land allocation method takes into account the variation of substitutability across different types of land use. It captures agronomic features included in the VALUE model. This modification gives a better representation of heterogeneous information of land productivity to the economic framework. Climate impacts and policy evaluation with ICES are reinforced due to the more refined system of land allocation. This exercise is original in its ability to base the analysis on empirically estimated parameters rather than on assumptions, as in other studies of this kind. Notably, we suggest diverse land Constant Elasticity of Transformation (CET) frontiers for two main ecological regions in the Mediterranean basin for a more accurate representation of agronomic characteristics. Using the modified ICES model we evaluate climate change impact on agricultural production in the Mediterranean region.

No abstract