A methodology to assess the impact of climate variability and change on water resources, food security and economic welfare Abdelaziz A. Gohar a,b, ⁎, Adrian Cashman b,1 a Department of Agricultural Economics and Extension, College of Agriculture, South Valley University, Qena, Egypt b Centre for Resource Management and Environmental Studies, The University of the West Indies, Cave Hill Campus, PO Box 64, Bridgetown, St. Michael, Barbados abstract article info Article history: Received 11 April 2015 Received in revised form 7 May 2016 Accepted 9 May 2016 Available online xxxx The potential impacts of climate variability and change on water resources and food security are receiving grow- ing attention especially in regions that face growing challenges meeting water demands for agricultural, domes- tic and environmental uses. Rainfed agriculture regions exhibit higher vulnerability to climate variability and change, whereaquifer storage and food security are under stress. Little research has attempted to investigate the consequences of climate variability and change on water availability and social livelihoods jointly. Employing available data on precipitation, farm budget data, and aquifer characteristics, a dynamic nonlinear optimization framework that maximizes the economic likelihoods of irrigation activities and food security under several cli- matic assumptions is developed and applied for Barbados as a numerical example. Our framework accounts for technological adaptation measure, drip irrigation, with the context of variable yield and cost of water demand under governmental subsidy schemes. Results indicate significant negative impacts of climate variability, change, and double exposure on future water resources and food security. However, some climate assumptions provide opportunity for some food producers who respond positively to technological adaptation programs, while con- sumers could face the major negative consequences by experiencing higher food prices. Our findings provide policymakers and stakeholders a comprehensive tool for economically efficient and sustainably reliant policy de- sign, implementation, and evaluation facing the potential climate variability and change impacts. © 2016 Elsevier Ltd. All rights reserved. Keywords: Climate change Climate variability Water resources Food security Positive mathematical programming 1. Introduction Understanding how climate variability and change might impact ag- ricultural production and food security is a challenge. Firstly, the eco- nomic consequences of climate variability and change on regional economies are not fully understood, especially the economic impact on different sections of society. Secondly, little attention has been paid to differentiate between the economic impacts due to climate change and those due to climate variability. While the physical impact of these two climatic events has been investigated, their economic conse- quences are treated as being the same, whereas they are dissimilar and give rise to different consequences. This study seeks to address this situation first separately and then jointly by investigating the potential impact of climate variability and change on farm income, food security, land use, and future water availability. It also considers the potential impact of adaptation measures. The mathematical framework that achieves this goal is developed and applied to Barbados as a numerical implementation example. The major components are described in the following sections. 2. Background Social and economic development depends on the availability and the sustainable management of water resources. Food production also relies on the availability of water at a given place and time, and this availability is also influenced by climatic conditions (Hammer et al., 2001). Over the last several years, the potential effects of climate vari- ability and change on water availability have received increasing politi- cal, social, and economic attention. Despite the levels of uncertainty associated with the magnitude and direction of climate variability and change, they are expected to have impacts on water resources availabil- ity, agricultural activities, and human, and ecosystem functions, includ- ing tropical regions (Cashman, 2014; Wang, 2014; Rasmussen et al., 2014). The anticipated climate variability and change are likely to im- pact water resources by altering precipitation patterns and intensity, duration and frequency of rainfall events. Such changes in the pattern and nature of rainfall regimes will have effects on surface water and groundwater availability (Vicuña et al., 2012; Ramirez-Villegas and Agricultural Systems 147 (2016) 51–64 ⁎ Corresponding author at: Department of Agricultural Economics and Extension, College of Agriculture, South Valley University, Qena, Egypt. E-mail addresses: abdelaziz.gohar@cavehill.uwi.edu, agohar@agr.svu.edu.eg (A.A. Gohar), adrian.cashman@cavehill.uwi.edu (A. Cashman). 1 Co-author. http://dx.doi.org/10.1016/j.agsy.2016.05.008 0308-521X/© 2016 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Agricultural Systems journal homepage: www.elsevier.com/locate/agsy