Inverse Geochemical Modeling and Hydrogeochemical Evolution Mechanism of Groundwater in Neyshabur Plain, NE Iran

The purpose of this study is to investigate the hydrogeochemical processes controlling groundwater resource evolution in the Neyshabur plain, northeast of Iran. The groundwater in the study area was divided into hydrochemical facies using cluster analysis. Two main groups of water were identified. Despite the fact that the types of water in both groups were the same (Na–Ca–Cl), the salinity of group 2 was considerably higher than that of group 1. Plagioclase (albite, anorthite) and feldspars in igneous rocks and metamorphic minerals increased the concentration of Ca²⁺ and Na⁺ in water. Due to the dissolution of calcite, dolomite, gypsum, and halite in carbonate and evaporitic sedimentary formations, Ca²⁺, Mg²⁺, Cl^–, Na⁺, and \({\text{SO}}_{4}^{{2 - }}\) ions were predominant in the water. Salinity was a result of the following primary reactions: (1) over-exploitation of groundwater; (2) dissolution of silicate minerals (albite, anorthite); (3) dissolution of carbonate minerals (calcite and dolomite); (4) dissolution of evaporative minerals (gypsum and halite). To address the deterioration of water quality as a first measure, the management of groundwater exploitation must be implemented to forestall groundwater degradation. Failure to adjust policies on groundwater extraction volumes by local authorities could result in a severe water scarcity crisis for the Neyshabur aquifer.