Quality analysis and nitrate map of groundwater resources in Alborz province (Hashtgerd Plain)

Discharging of pollutants produced by municipal developments, agricultural and industrial activities and climate change are among the issues affecting the quality of groundwater resources. Groundwater is one of the valuable resources that lack of proper management can transfer chemical pollutants through industrial and agricultural effluents. In relation to the influence of these factors, we can mention the changes in the groundwater level of Hashtgerd Plain which has fallen by about 15 meters over the past three decades. The innovation of this research is to use Satellite Images and monitor the quality of water resources status by identifying the factors affecting the quality of groundwater resources and studying soil and water resources conservation strategies.

In this research, 24 samples (from 24 wells) obtained from different parts of Hashtgerd plain were prepared. The concentration of effective parameters on the quality of groundwater resources, including Nitrate, Sulfate, Calcium, Sodium, Magnesium, Potassium and total dissolved solids was self-measured using the standard reference method. Then the interpolation (Error estimation of interpolation methods) and quality analysis of ground water resources were investigated by Arc Map and AquaChem software’s. Land-use changes were also investigated using Landsat 8 satellite imagery (OLI sensor) and ENVI software’s. Then the obtained results were used to study the spatial variation of the quality parameters and identify the factors affecting the quality of groundwater quality changes.

The results obtained from the analysis semivariogram and the error estimation of the interpolation methods in this study for the nitrate parameter (1394-1394) show that the nugget effect ratio with sill from 0.12 to 0.17, indicating spatial continuity Strong is this parameter. In addition, the interpolation methods, the Empirical Bayesian Kriging method, had the lowest root mean square error (2.99). The results of the study of spatial variations of nitrate values in Hashtgerd plain groundwater resources indicate that the highest amounts of this pollutant (more than 50 mg / l) were located in the urban and industrial users (Arab Abad kouh, Qaleh Soleimani) Which can be linked first with municipal wastewater and then with the application of nitrogen fertilizers in agriculture. In addition to the above, the study of spatial variations of sulfate and groundwater ion ratios in the years 1391-1394 show that the values of this parameter in parts of the gardens and agriculture of the plain (central parts) more It is about the standard (more than 400 mg / l). The main cause of this increase is known as Hydrochemical reactions and factors.

In general, the results of this study showed that the number of effective parameters in determining the quality of groundwater resources of Hashtgerd plain exceeds the standard limits. In addition, the groundwater level has dropped (9.71 m) during the study period (1394-1394).. In addition, due to the intensive impact of human factors on reducing the quality of groundwater resources in the Hashtgerd plain and reducing groundwater levels during the study period (1394-1394), consideration the groundwater protection area and management of groundwater pumping wells is essential.