Ground Water Modeling to Estimate Nitrate Dispersion in Critical Aquifers (A Case Study: Mashhad City)

At present, due to inefficient and incorrect management, most domestic aquifers in Iran, particularly in dry regions, including the Mashhad plain, face lowering levels of lakes and ponds in water storage and are sometimes subject to various pollutants. In fact, a main and significant index which shows the aquifers infections is that nitrate is found in water. In this research, an attempt has been made to prepare a mathematical model for qualitative and quantitative value of the Mashhad plain aquifer. Consequently, the aquifer’s behavior is predicted and simulated based on nitrate ion during the last twelve years.In order to develop a mathematical model for qualitative and quantitative value of Mashhad plain’s aquifer, meteorological, hydrological and hydro geological data and statistics were analyzed using Surfer Ver. 8 software, computer code Modflow 2000 and GMS processor. After calibration settings and verification, this mathematical model is achieved.Results indicate that in the year 2022 the problematic issue of nitrate infections will remain intact for most central and eastern parts of the Mashhad aquifer and its density in these regions varies from 10 to 90mg. Based on this information, in most regions nitrate density is more than the permitted amount (45mg per liter) and the annual mean drop value for this aquifer (0.90 meter) shows its critical situation.The main reason for this aquifer’s pollution during recent years is non-standard waste gathering and sewage burying methods and combination with water wells, thus its penetration through these water wells into the aquifer.