Background and Purpose: Elevated nitrate concentrations in drinking water can cause methemoglobinemia in infants, stomach cancer in adults and nitrate poisoning in animals as well. Modeling of nitrate fate and transport in groundwater to minimize nitrate concentration in groundwater has been studied by numerous researchers.

Materials and Methods: In order to determine the potential nitrate and nitrite ions contamination of groundwater, 93 groundwater samples were collected. All the observation wells were located in agricultural areas. In order to measure the amount of nitrogen in the soil, 45 samples from the entire region were randomly selected and analyzed.

Results: The results showed that in 82% of groundwater samples nitrate concentration has exceeded the standard level of 10 mg/l as N. Water level in orchard fields were between 1m to 3.7 m below the ground surface. Nitrate concentration in all samples from the citrus orchard fell within the standard levels. Simulation of potential nitrate movement was performed in 4 different areas. Results indicated that in the rice field nitrate penetrated to the depth of 3.2 m that was the deepest nitrate seepage between four areas. Probable reasons of different results in these areas are discussed.

Conclusion: The simulated and observed measured data showed that the model was able to predict the groundwater quality changes within the soil profile and the aquifer.