Evaluation of intrinsic vulnerability of Ardabil plain using DRASTIC, SINTACS and SI methods

growing of population, development of agricultural and industrial activities were intensively increased the consumption of water resources, as results, the water quality and quantity have been decreased. Vast declining of fresh groundwater resources levels and infiltrations of surface runoffs and precipitations into groundwater, were decreased the runoffs dramatically and, as a consequence, the groundwater resources became as an important part of the water resources for drinking, industrial and agricultural demands in all over the country. Therefore, the importance of groundwater preservation, management and prevention of its contamination becomes as an inevitable task. One of the effective solutions to prevent the contamination of groundwater is to distinguish the vulnerable areas of the aquifer. In this study, DRASTIC, SINTACS and SI methods are used for assessment of vulnerability of the Ardabil plain aquifer. Using from these methods and with respect to the hydrological and hydrogeological characters of the study area, zoning of the vulnerability of aquifer to contamination is carried out and then susceptible areas to contamination was distinguished in each method. The measured nitrate concentrations in the area were used to validate each method. Correlation Index (CI) between vulnerability maps and nitrate amounts were calculated for exact and better comparing of these methods. Results showed that DRASTIC model has the highest CI, this means it is better than other methods for vulnerability assessment. According to the results of DRASTIC, 44.36% of the Ardabil plain aquifer area, located in the eastern and southern part of the plain, has low vulnerability and the rest parts including northern and western part of the plain has moderate vulnerability.