The present study describes the hydrochemistry of ground waters found in Mesta River Basin, located south-western part Bulgaria. groundwater’s composition can be expressed as follows: Ca2+ > Na+ Mg2+ K+; K+ equivalent units for cations, and HCO3– SO42– Cl– anions. chemical studied groundwater described calcium-bicarbonate. calcium ions make up from 17.90% to 38.62% (30.18% on average), bicar...