Role of Mehriz Fault in hydrochemical evolution and groundwater flow of Yazd aquifer, central Iran

Yazd-Ardakan catchment which is located in arid areas of central Iran is the largest basin in Yazd province, comprising one of the most important groundwater aquifers. There is a small but significant freshwater zone near Yazd city, which supplies about 20% of the city’s water surrounded by saline waters. To protect and manage the fresh groundwater in the study area, the origin of freshwater and its transport mechanism to the study area is the present study’s research motivation objective. The chemical composition of 107 water samples, water levels in 27 observation wells, and previous geological and geophysical reports and surveys were used to investigate the processes controlling flow patterns in this typical arid-land alluvial aquifer, considering the main role of the Mehriz fault zone on the groundwater system. In terms of hydrochemistry, the significant changes in water quality are observed around the fault zone, approving the main role of the fault on the groundwater system. Groundwater flow lines are locally co-directed with the Mehriz fault, confirming its barrier characteristics in alluvial sediments, while the groundwater is passing through other parts, mostly in nearby hard-rock formations. Based on the results, Mehriz fault locally emerges as a conduit in which freshwater is carried to the area with poor quality, supplying drinking water for Yazd City. Comparing water resources on both sides of the fault, quantitatively and qualitatively, confirmed that the Mehriz fault acts as a complex barrier-conduit system. © 2021, Saudi Society for Geosciences.