Monitoring Trend of Changes in Some Qualitative Parameters of Jiroft Plain Groundwater Resources

Background an Objectives
Iran’s groundwater resources are considered as a vital water supply for a number of reasons, and inconsiderate usage and exhausting these vital resources would bring about a severe water crisis in the country. Underground waters are usually consumed for different purposes ranging from drinking and agriculture to industry, so that the quality measures of these resources depend on the main purpose that they are intended to be used. Consequently, different standards of quality restrict the water consumption in order to reduce harmful effects of them. Furthermore, Water quality is generally an extremely important subject in water studies, and identifying and analyzing the chemical compounds in groundwater resources could be beneficial in agricultural studies. In agriculture, both water quality and quantity play 2 part, and poor quality could certainly become a primary restricting factor in water usage. This can cause undeniable farming problems and could damage the soil as well. In this regard, the necessity of providing a proper, well-planned management system for monitoring and controlling water quality is of a great importance.
Over the past years, in many parts of Iran, including Jiroft, in which this study is carried out, because of some important issues such as the growing population, frequent periods of drought and inconsiderate using of the dwindling supply of groundwater, the quality and quantity of these waters are rapidly diminishing. As the livelihood of a huge number of local people who lives in the region of Jiroft, depends on agriculture, the effective management of these water resources needs better and more up-to-date information about these resources. Having such data could definitely help us to be aware of recent changes and to be able to make better, informed decisions. The main purpose of this study would be analyzing the changes of chemical parameters in underground waters of Jiroft plain.
Methodology
 Hydro-chemical analysis of Jiroft’s groundwater resources for agricultural consumption is our primary goal in this research. In order to achieve this goal, we gauged and analyzed different chemical parameters including electrical conductivity (EC), total soluble solids (TDS) and acidity (pH) in 30 samples of the wells with suitable dispersal in the region in the years of 2011 and 2018. To understand the spatial distribution of suitable areas, ArcGIS 10.5 software is used and the data layers were prepared.
 
Findings
 The results of the Wilcox diagram show that most of the samples are in class C₂-S₁, which is a sign of a low salinity line and therefore they are applicable in agriculture. Besides, a limited number of samples are in class C₃-S₁, C₃-S₂ and C₄-S₂, which have high salinity line and are consequently ideal for irrigating the plants that are not sensitive to salinity. It is noteworthy that none of the samples has a low salinity contamination (C₁-S₁). Considering the fact that most of the samples in the study area are in the range of C₂-S₁, they could be suitable for irrigation. According to the Wilcox diagram, the quality of agricultural water in the groundwater samples in Jiroft is in a good and mostly moderate category. Our research finding shows that TDS variations is between 320 and 2048 mgL^-1, and pH variations is between 6.6 and 8.6, and therefore they are ideal for irrigation purposes.
 Conclusion
 During the statistical period, the level of water reduction is increasing; although, in some years, the number is lower. These considerable changes confirm frequent droughts and a vast amount of underground water consumption. In this situation, diminishing groundwater quality would be inevitable and if this trend continues, the quality level of these waters will be reduced gradually. In the years when water level reduction is lower than others, we can see higher level of rainfalls or even floods in which took place in the region frequently in recent years. This naturally fuels Jiroft’s aquifers and decreases the level of water reduction. According to the zoning map of the distribution of groundwater quality parameters, the Jiroft plain has a suitable quality for agricultural purposes. Only in the southwestern margin and some other parts of the plain, the groundwater quality is lower and could not be suitable for farming purposes. Overall, most areas of the plain are of good quality and suitable for agriculture.