Abstract
Groundwater resources are critically important for irrigated agriculture in Tunisia. However, excessive irrigation extractions where groundwater is slowly renewed are causing a widespread depletion of the aquifer systems, with the impacts of climate change expected to further exacerbate this problem. These circumstances call for the development of methodologies and analyses that can support the design of sustainable groundwater management policies. This paper presents a hydro-economic mathematical programming model that is used to evaluate the effects of different policy measures for reducing aquifer depletion in the Cap-Bon region of Tunisia. Three policies have been evaluated: a quota defining the maximum quantity of groundwater extractions, environmental taxation, and supply expansion with subsidized desalinated seawater. Overall, results highlight the economic and social tradeoffs among these different policy choices and the challenges facing the implementation of sustainable groundwater management in Tunisia. More specifically, results show the advantages of using subsidized desalinated seawater compared to the other two policy alternatives in terms of the value of agricultural production, farmers’ profits, and employment, despite of its sizeable budgetary burden.
Highlights
Irrigated agriculture plays an important role in securing global food production, and sustaining locally rural livelihoods and ecosystems
Results of Policy 2 that introduces an environmental tax on groundwater extractions indicate that the optimal environmental tax that reduces extractions up to the natural recharge of the aquifer is equal to 0.77 dt/m3
Results of Policy 3 that expands the supply of water with subsidized desalinated seawater indicate that for a full elimination of groundwater depletion in the area, the government should provide a subsidy of 0.83 dt/m3 (75% of the cost of seawater desalination equal to 1.15 dt/m3)
Summary
Irrigated agriculture plays an important role in securing global food production, and sustaining locally rural livelihoods and ecosystems. It is estimated that 17% of agricultural lands are irrigated, yet they account for 40% of the global food production (Abdullah, 2006). Irrigation is the main user of water resources worldwide, and especially in arid and semiarid regions (Shiklomanov, 2000). Groundwater represents the world’s largest freshwater resource and is critically important for irrigated agriculture (Koundouri, 2004). Depletion is widespread in large groundwater systems in both semi-arid and humid regions of the world (Konikow, 2011). Excessive extraction for irrigation where groundwater is slowly renewed is the main cause of the depletion, and NEW MEDIT N. Excessive extraction for irrigation where groundwater is slowly renewed is the main cause of the depletion, and NEW MEDIT N. 4/2018 climate change has the potential to exacerbate the problem in some regions (Wada et al 2012)
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