Groundwater Recharge Area Based on Hydrochemical and Environmental Isotopes Analysis in the South Bandung Volcanic Area

The determination of recharge areas needs to support the groundwater conservation in the southern volcanic Bandung area. This study aims to determine the recharge area based on environmental isotopes and hydrochemical. A sampling of 26 groundwater was carried out at springs, dug wells, and drilling wells. The variation in groundwater chemistry principally is controlled by a combination of ion exchange, silicate weathering, calcite, and dolomite dissolution of minerals. The hydrochemical facies were CaCl, CaMgCl, CaMgHCO3, CaHCO3, and NaKHCO3. The CaHCO3 facies describe moderate groundwater flows. The NaKHCO3 facies shows the mixing of shallow and deep groundwater. The recharge area in the central, proximal, and medial facies zone consists of 3 groups. Group I is considered water originating from local rainwater infiltration; Group II is considered the infiltration elevation which ranges from 980–1230 m asl; Group III estimated to be derived from the recharge elevation between 750–970 m asl, Group IV are more likely to show symptoms of evaporation or interaction with surface water. The discharge area is characterized by less active groundwater circulation, with dominant HCO3– and TDS value in the distal facies zone. Hydrochemical variation helped the identification of recharge areas in the volcanic facies.

Spatial and Temporal Hydrochemical Variation of a Third Order River Network in a Quasi Pristine Coastal Watershed, at Southern Bahia, Brazil

ABSTRACT Rio da Serra watershed presents well preserved fragments of rain forest at the headwaters and small farms at middle and final stretches. These features allowed the study of fluvial hydrochemistry, under quasi pristine conditions. Sampling stations were established in order to represent the basin, and visited during dry, intermediate and wet periods. Obtained results are: temperature (22.1 – 28.6 °C); electric conductivity (34 – 52 µS/cm); dissolved oxygen (35 – 110%); pH (3.8 – 7.7); total suspended solids (1.1 – 20 mg/L); chlorophyll (1.0 – 9.2 µg/L); total N (74 – 580 µmol/L); particulate N (60 – 550 µmol/L); N-NO3 (0.1 – 9.3 µmol/L); dissolved organic N (4 -70 µmol/L); total phosphorous (5.3 – 47 µmol/L); particulate P (4.4 – 59 µmol/L); P-PO4 (0.1 – 0.7 µmol/L); dissolved organic P (0.01 – 2.0 µmol/L); silicate (30 -90 µmol/L); fecal coliforms (80 – 700 CFU/100mL). In seasonal terms dissolved oxygen, electric conductivity, nitrate and silicate concentrations were higher during the dry, whereas TSS was higher during the wet period. Seasonal differences of dissolved oxygen, temperature, pH and nitrate were also detected near wetlands areas. Along the basin results showed a distinction between headwaters and other sections, revealing a control of fluvial hydrochemistry by the preserved area, mostly for the dissolved organic N and P species and phosphate.