Isotope method for uncover characteristics and recharge areas of groundwater in Pangkalpinang City, Bangka Belitung Islands Province

Abstract Groundwater recharge areas have an important role in water resources management, especially in maintaining the sustainability of groundwater in terms of quantity and quality. However, groundwater recharge areas whose water is utilized as one of the sources of clean water for the people of Pangkalpinang City have never been studied before. Based on these problems, this study was conducted with the aim of knowing the groundwater recharge area and the isotope characteristics of groundwater utilized by the community in Pangkalpinang City. 3 rainwater samples, 1 spring sample, 5 groundwater samples from dug wells, and 8 groundwater samples from drilled wells were taken directly and analyzed for 2 H and 18 O isotope content. The analysis results showed that rainwater 2 H values are -2,4 0 /00—8,0 9 0 /00 and 18 O -9,7 4 0 /00—52,8 5 0 /00. Spring water has values 2 H -8,09 0 /00, 18 O -42,24 0 /00. Borehole water has 2 H values of 5,8 6 0 /00—7,3 2 0 /00 and 18 O -35,9 2 0 /00—45,2 8 0 /00. They dug well water that has values of 2H 3,8 0 /00—6,83 0 /00 and 18 O-24,8 5 0 /00—41,7 8 0 /00. The results of rainwater data plotting show that springwater, dug well, and drilled well water enters the hydrological cycle or meteoric water. For spring water, borehole water and some dug well water interact with each other and are not affected by evaporation. They are in the same aquifer system or may tend to come from the same source. Still, there is 1 dug well (SG-52) that moves away from the meteoric water trendline, so it can be interpreted that the well water evaporated during the journey from the recharge area. The groundwater recharge area in the study site is located at elevation 67,68-204 masl or outside of the study site, and the groundwater recharge area is most likely along the south to northwest side of the study area.