Assessing the effect of water scarcity on crop selection and spatial pattern of croplands in central Iran

Abstract

Farming and food production for the increasing world’s population require proper preparation of a diverse range of environmental parameters especially water availability and accessibility. This study investigated the effect of water scarcity on crop selection and spatial pattern of croplands in an agricultural landscape in central Iran. Towards this aim, the main crops including wheat, alfalfa, potato, fruit trees, rice and vegetables were mapped using a combination of decision tree and object-based classifiers and four Landsat 8 images acquired from March 2015 to June 2015 with Kappa Coefficient and Overall Accuracy of 80.16 and 85.37 percent, respectively. Groundwater depth as an indicator of water availability was mapped by interpolating over 13 thousand wells and, according to the ability of farmers and available technologies to extract water, classified into four groundwater level areas (GLA). Finally, spatial pattern of crops in each GLA was investigated using four landscape-level metrics including Mean Patch Size (MPS), Mean Nearest-Neighbor distance (MNN), Contagion index (CONTAG) and Shannon's diversity (SHDI). The results of this study showed that cropping system in drier areas has shifted towards monoculture (crops with fewer water requirements such as wheat) and led to a fragmented and homogeneous landscape with large and low dispersed agricultural units. It was finally concluded that changes in crop selection and spatial pattern of croplands could be considered and applied as a precise and fast indicator of determining water availability and accessibility over large geographical regions in Iran.