The qualitative and quantitative trend analysis of groundwater in Jiroft plain using Modified Mann-Kendall Test

As a dry province in the center of Iran, Kerman has faced a major groundwater depression over the past few years. Reduced groundwater levels in this region have created myriad problems in the agricultural sector, particularly in the southern and southeastern areas with relatively warmer weather. In this research, the temporal and spatial trends and  change-point time of quantitative and qualitative variables of groundwater (EC, pH, Na, Ca, Mg, Cl, SO4, HCO3, TDSand groundwater) in Jiroft plain were investigated during 2002-2015. The  results revealed that, on average, the water level of the studied plain was significantly reduced by approximately 8 meters during the statistical period at a significant level of 5%. The central areas of the plain were reduced. A year after the change-point of groundwater data, a significant increase was observed in the qualitative data in the region. The highest increase in groundwater salinity was also found in the main river route, indicating a reduction in surface water discharge in the aquifer. During the specified period, the amounts of Ca, EC, Cl, SO4, Mg and Na in  the studied plain increased (decreased) by an average 27, 18, 40, 0.4, (-24) and (-2.3) %, respectively. In 2007, the  decline trend of groundwater levels in Jiroft plain was, on average, significant and failure was observed in the data. Finally, the groundwater quality in Jiroft plain was investigated using the Wilcox diagram, which  showed that agricultural water in certain areas with C2-S1 classes was acceptable.