Spatial evaluation of qualitative parameters of groundwater resources with the aim of its application in agriculture and drinking (Case study: Mehvalat-Feyzabad plain)

The reduction of groundwater level in the plains of Khorasan Razavi Province has caused the destruction of groundwater quality and salinity of water resources. This has happened more intensely in Mehvalat plain. Since groundwater in this plain is often used for agriculture and drinking, so knowing the quality of groundwater for use in these two sections is important. Therefore, the purpose of this study is to evaluate and zone water quality variables for two types of drinking and agriculture consumption.

PH, permeability index (PI), sodium absorption ratio (SAR), and electrical conductivity (EC) variables have been selected to evaluate the water quality suitable for agriculture and irrigation. Also, the quality of drinking water was compared with the international and national standard indicators. Spatial interpolation methods are now widely used to monitor spatial variations in water quality. In order to zone water quality parameters, a kriging method that is preferable to other geostatistical methods was used.

SAR in irrigation water can be used as an indicator to determine the risks of soil sodium contamination. This index was studied for Mehvalat-Feyzabad water wells and is in the middle range. 68% of the study area is in the appropriate class in terms of irrigation water PI and 32% is in the relatively suitable range and no points were found in the inappropriate class. According to the spatial zoning map, pH is in the allowable range of 7 to 8.5 and the EC of water is in the range of low salinity to very saline. The best EC linear relationship with cations, anions, and TDS (Total Dissolved Solids) was presented for the study area in this study. Examining the relationship between these three variables shows that the increase in EC indicates an increase in the amount of cations, anions, and TDS and will affect the consumption of this water for agriculture and drinking in the future.

Due to the fact that the salinity of water for agricultural use was assessed from low salinity to very saline, so leaching and drainage should be done and the type of cultivation should be selected according to the salinity. For areas that are in the very saline group, it is necessary to use salinity-resistant plants with good drainage and low planting frequency. Examination of drinking water quality in the area showed that its use is not suitable for drinking.