Vulnerability Assessment of Sabzevar Aquifer (Northeast of Iran) Using Drastic Model

In countries with arid and semi-arid climates, conserving water resources is important. For this purpose, different models were presented to determine the vulnerability of areas. In this research, a vulnerability map of Sabzevar aquifer has been prepared using a drastic model. Sabzevar aquifer located in the northeast of Iran with an area of 5455.4 square kilometers has a dry and desert climate with hot and dry summers and cold winters. The drastic model is obtained through 7-layer overlap (groundwater depth, net nutrition, aquifer environment, soil type, topography, influence of unsaturated area and hydraulic conductivity of the aquifer) and shows a detailed map of the aquifer vulnerability. ArcGis10.5 software was used to draw the drastic model map. The numerical value of the drastic model in the study area is between 81 and 159 (from low vulnerability to high vulnerability). Drastic map showed that a very small area from the west of the study area has low vulnerability and the central areas of the plain have high vulnerability. Other parts of the region are moderately vulnerable. Shallow groundwater depth in the central areas of the plain and also low slope in the above area has the greatest impact on the vulnerability of the region. Due to the volume of agricultural activities in the central areas of the plain, measures should be taken to prevent possible contamination of the aquifer. Due to the fact that the concentration of nitrate in groundwater sources was not available in the study area, so electrical conductivity was used to validate the zoning of the drastic model. The overlap of electrical conductivity with the drastic map showed that the electrical conductivity was high in the center of the vulnerable plain. This can also confirm the accuracy of the drastic model.