A survey on spatial and temporal variations of groundwater quality and quantity index using Geographic Information System and Geostatistics (Case study: Bam- Narmashir plain)

This research set out to determine the qualitative and quantitative characteristics of groundwater resources in Bam-Narmashir plain by using Geographic Information System and Geostatistics.

In this regard, the geostatistical method of Kriging and Geographic Information System was used to investigate the spatial distribution of qualitative characteristics (e.g., chlorine content, electrical conductivity, dissolved solute concentration, magnesium, potassium, acidity, sulfate, and bicarbonate) and the groundwater quality index (GQI) as well as the depth of ground water in the ten-year statistical period of 2011-2021.

The results of the preparation of spatial distribution maps of water quality variables in the statistical period revealed an increase of the value of these parameters (except for the pH variable) from the south to the north of the plain. So that from the middle of the plain to the north, this increasing trend becomes more intense. The results of preparing the difference map of GQI index during the 10-year period under investigation indicated that the quality of ground water improved in a small area of the plain and in other areas of the plain, especially in the northern parts, the difference of this index at the beginning and end this period increased by more than 400 units. This issue shows the severe drop in water quality during this period in most parts of the plain. The results of the groundwater depth change map disclosed that, except for a very small part in the middle parts of the plain, in other parts of the plain were observed a drop in the level of underground water reported to be 52 meter in the most western part of the plain and on average about 9.8 meter in other parts of the plain.

The results of this research showed that the quality of ground water was good for drinking purposes in a very small part of the south of the plain as an except, having an unsuitable for drinking purposes category in other parts of the plain. Overharvesting and lowering of the aquifer's water level has caused the rise of salt water and the interference of the salt and fresh water table in all areas of the plain especially its central areas, which the continuation of this process can increase the salinity of the aquifer to such an extent causing deterioration of all activities in agriculture and animal husbandry in the region. Furthermore, in the results of quantitative study of ground water indicated a strong and increasing trend in the amount of exploitation leading a decrease in the level of groundwater.