Determination of Optimum Cropping Pattern for Groundwater Stability

Groundwater is the largest source of freshwater available on Earth, which has been threatened with extinction in many countries due to overdraft. Determining the optimal cropping pattern along with a reduction in water resources allocation that does not lead to a reduction in farmers' income can be an appropriate strategy for groundwater sustainability. In the present study, a method has been proposed that, in addition to the sustainability of groundwater, minimizes farmers' loss of income. For this purpose, four groundwater use scenarios were first defined and groundwater level changes were calculated for each scenario using Neyshabur Decision Support System model. Also, economic productivity of water was estimated using a questionnaire for 242 agricultural wells and 9 dominant plants in Neyshabur plain, in 2016. To minimize farmers' income reduction, water was reallocated to different crops and the areas of cultivation were determined based on the ratio of economic productivity percentages of each crop. Due to changes in groundwater level and existing conditions, the scenario in which groundwater use was set equal to renewable water (414.9 M.m3) was selected as the best scenario. Implementation of this scenario would reduce the allocation of 227.5 M.m3 for groundwater sustainability. The results showed that the reduction of water allocation would result in a decrease of 27061 hectares of cultivated land area and a decrease of about 83.5 billion Tooman (local currency) in revenue. In order to compensate for the decrease in income, alternative crops of pistachio and saffron were suggested due to their higher economic efficiency and lower water consumption. In the proposed pattern, 18,000 hectares of saffron or 4473 hectares of pistachio replace the current crops that have the highest percentage of cultivated land in summer vegetables and sugar beet.