Using hydrogeochemical facies and signatures for groundwater characterization and evolution assessment in aquifers with contrasting climate and geology in Tanzania

Abstract This study aimed at characterizing groundwater evolution using hydrogeochemical facies and signatures in two basins with contrasting climate geology, one the central part other eastern coast of Tanzania. The Kimbiji (humid, unconsolidated) aquifer is covered by an unconfined layer upper parts a confined lower parts, strong artesian flow characteristics while Singida (semi-arid, consolidated) occurs weathered shallow layers fractures basement rocks. Fieldwork involved water sampling from precipitation, deep boreholes, springs surface rivers lakes areas. These were specifically conducted for analyses to unravel aquifers. Physico-chemical quality parameters [i.e., pH, electrical conductivity (EC) total dissolved solids (TDS)] measured situ HANNA HI 9829 Multiparameter Analyzer. Standard procedures sampling, preservation, transportation, chemical major ions as documented previous studies. Samples carried stored 4 °C prior their shipping Water analysis testing environmental regions (WATER) laboratory Iringa, mechanism controlling geochemistry revealed assessing reactions between minerals. Chloro-Alkaline indices (CAIs) used cation exchange processes its host environment stagnancy and/or during travel. Gibbs ratio 1 values found range 0.26 0.94 2 ranged 0.11 0.95. majority samples irrespective contrast geology observed fall rock–water interaction zone. attributed weathering where dissolution rock forming minerals takes place. Some exhibited replacement Na + Ca 2+ or Mg (S18), loss through precipitation evaporate rocks (S11, S13, S16, S19), flowing crystalline (S1, S2, S4, S6, S8, S10, S12, S14, S21). : > 1.0 S17, S18, S19, S21) explains base ion < implies reverse (S2, S11, S16).The SO 2− HCO 3 − connotes normal hydrological cycle greater than indication –Cl brines (S16, S19). Cl divided into course, recharge (S52, S54, S56, S57, S58) discharge zone, (S53, S59, S60, S61) which course. Interestingly, K ratios well confirmed that course (discharge zone). confirm dominance it has been explained CAIs Piper diagram . diagrams hydrochemistry aquifers are mainly region, affirming there high thus main controls mineralization similarity distant body, Lake Inkhanoda Mwankoko borehole discernible water, further revealing fed sub-regional regional systems.