Drastic model optimization in vulnerability assessing of Meymeh aquifer to Nitrate Contamination

Abstract

Locating and identifying vulnerable areas of the aquifer and managing water supplies use and land use is a good approach to preventing underground water pollution. Nitrate has always been considered as a water pollution index. The aim of this study was assessing the vulnerability of Meymeh aquifer to nitrate through GIS, statistical methods, and Drastic Model. Drastic Model identified the vulnerability of Meymeh Aquifer as low and medium (75-128). After calculating the drastic new index using Raster Calculation in ArcGIS, the correlation between nitrate concentrations in groundwater samples and the new drastic index was calculated. The correlation coefficient of -0/162 (before optimization) to0/842 (after optimization) has increased. These correlations were significant at the 95% probability level (P-value <0/05). To gain nitrate concentration maps, samples were taken through standard sampling principles from 10 wells and analyzed through spectrophotometry approach. Next, nitrate concentration maps were drawn using interpolation models. Combining vulnerability map and nitrate concentration map indicates that most of the area under study was safe and low-risk and only one area of Meymeh was a high-risk area with nitrate concentration above 50 milligrams per liter in underground water. According to the nitrate concentration zonation map, The highest concentrations were observed in groundwater in the southern region of the Meymeh aquifer is due to the interaction of pollution caused by farming activities, Return water irrigation, Lithology, Higher nutrition rates, Hydraulic Conductivity and The permeability of the soil.

Keywords

• drastic model
• nitrate contamination
• gis
• meymeh aquifer