Impacts of urbanization on the groundwater resources in Shahrood, Northeastern Iran: Comparison with other Iranian and Asian cities

Abstract

Urbanization may lead to the contamination of groundwater and/or it may alter the hydrogeological regime. Shahrood is a medium size city in northeastern Iran, underlain by an alluvial aquifer. Analysis of 45 samples collected from the Shahrood Plain’s aquifer in 2003 and 2005 revealed that: (1) Shahrood’s wastewater disposal wells and deep cesspits have led to the nitrate pollution of groundwater (up to 140 mg/L NO 3–NO 3); (2) urban recharge has lowered the groundwater temperature and pH and (3) urbanization has possibly resulted in the incomplete interaction between various flow compartments of the aquifer. In four other Iranian cities, Gorgan, Kerman, Zahedan and Mashad, urbanization has led to water quality deterioration, alarming rise of groundwater levels endangering foundations of the buildings as well as collapse of ‘qanat’s galleries. The maximum concentration of nitrate (MCN) in groundwater in all these cities has been compared with the ratio of population/rainfall in each city. A similar exercise has been carried out for Asian megacities. These show that MCN in an urban aquifer is directly controlled by population and average annual rainfall. This has serious implications for the management of urban groundwater resources and suggests that the current world population growth rate and the likely reduction in the atmospheric precipitation induced by global warming will further deteriorate the quality of such resources.