Investigation and Determination of the Spatial Distribution of Nitrate and Electrical Conductivity in Groundwater by Geostatistical Method (Case Study: Kabudrahng Plain)

Subject Areas : Agriculture and Environment

Omid  bahmani ¹ (Assistant Prof., Department of Water Engineering, Bu-Ali Sina University, Hamedan *(Corresponding Author).)
Adel  zali ² (M.Sc., Irrigation & Drainage, Bu-Ali Sina University, Hamedan.)

Received: 2016-05-01 Accepted : 2016-09-28 Published : 2021-07-23

Keywords: Nitrate, geostatistical, plain Kabudrahng, GIS, EC,

Abstract :

Background and Objective: Nitrate contamination in drinking and agricultural water is increasing in the Kabudrahng plain. Farmer's Tendency to use a variety of animal and chemical fertilizers has increased the amount of nitrate in groundwater in this region. This study aims to determine the most appropriate geostatistical methods to analyze the spatial variation of nitrate and electrical conductivity of the Kabudrahng groundwater plain.Material and Methodology: The trend of nitrate changes and groundwater electrical conductivity in 41 and 152 wells were investigated using MNITAB16.2 software and the most suitable geostatistical method was determined with ARCGIS9.3 software. To determine the most appropriate geostatistical methods for zoning nitrate and groundwater electrical conductivity used the ordinary kriging (OK), simple kriging (SK) and the specific methods include the inverse distance, weights (ID(, radial basis functions (RBF), global polynomial interpolator (GPI) and local polynomial interpolator (LPI) with ARCGIS9.3.Findings: The results showed that the best method for zoning the electrical conductivity was the RBF method with RMSE=837.07, MAE= 548.01 and R=0.841 and simple kriging (SK) with RMSE=900.68, MAE=581.8 and R=0.699 and the best way to zoning the nitrate was the RBF method with RMSE=3.76, MAE=2.42 and R=0.351 and ordinary kriging (OK) with RMSE=3.86, MAE=2.51 and R=0.372.Discussion and Conclusion: According to the standard of California, 8 percent of the plain area had an electrical conductivity less than 700 μmho/cm, 77 percent between 700 to 3000 μmho/cm, and 15 percent above 3000 μmho/cm. The distribution of nitrate concentrations showed that about 85.57% of the area was lower than 5 mg/liter, 14.43% between 5-30 mg/l,  and there was no severe pollution in the plain. The spatial distribution pattern indicated that high levels of electrical conductivity were observed in the western and southwestern parts of the plain. The amount of nitrate in groundwater was in the good range, but in southern and southwestern plains was higher than the standard.

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