Using stable isotopes and major ions to identify recharge characteristics of the Alpine groundwater-flow dominated Triglavska Bistrica River

Triglavska Bistrica is a typical Alpine river in the north-western part of Slovenia. Its recharge area includes some of the highest peaks in the Julian Alps. The hydrogeological conditions and flow of the river depend largely on groundwater exchange between the karstified aquifer in the carbonate rocks and the intergranular aquifer in the glaciofluvial deposits. The average volume of the river flow is up to several m3/s. In this study, water samples from different locations along the river were analysed for stable isotope ratios of oxygen and hydrogen, major ions, and concentration of tritium activity. The correlation of major ions suggests that the recharge area consists of both limestone and dolomite rocks. The δ18O and δ2H values decrease downstream, implying that the average recharge elevation increases. At the downstream sampling site V-5, located approx. 300 m upstream from the confluence of the Sava Dolinka River, the calculated mean recharge altitude is estimated to be 1,996 m.

Studi Hidrogeofisika Gunung Malabar Sebagai Gunung Tertinggi pada Sistem Hidrologi Cekungan Bandung

Gunung Malabar merupakan gunung tertinggi pada gugus pegunungan yang mengitari Cekungan Bandung Purba. Kawasan ini tersusun oleh berbagai pegunungan kecil, yaitu Gunung Haruman, Gunung Puntang dan dataran tinggi Pangalengan. Vegetasi di kawasan Gunung Malabar masih cukup lebat dan kawasan ini juga sering mengalami hujan dengan intensitas yang tinggi. Kondisi tersebut menjadikan Gunung Malabar sebagai recharge area dan catchment area yang ideal dengan area cukup luas. Artikel ini mengulas hasil penelitian hidrologi menggunakan metode geofisika untuk mengkaji pengaruh kawasan Gunung Malabar terhadap sistem hidrologi Cekungan Bandung Purba. Metode yang digunakan pada penelitian ini adalah Resistivitas-DC dan Very Low Frequency. Selain itu, pengukuran sifat fisik dan kimia air juga dilakukan untuk mendapatkan nilai kualitas baku mutu air permukaan berdasarkan parameter TDS, pH, dan EC. Pengukuran Resistivitas-DC dilakukan di dua wilayah yaitu di Lereng Utara Gunung Malabar, diperoleh rentang nilai resistivitas air tanah sekitar (1.4-70)Ωm, sedangkan di lereng barat Gunung Malabar, diperoleh rentang nilai resistivitas air tanah sekitar (20-150)Ωm. Kombinasi metode Resistivitas-DC dengan VLF di lereng barat Gunung Malabar menunjukkan bahwa recharge area dari sistem hidrologi di Gunung Malabar terbentuk pada zona lapisan dangkal (sekitar 15 m) dan menengah (sampai dengan 40 m). Selain itu, studi ini juga menunjukkan kualitas air tanah di kawasan Gunung Malabar. Hasil yang diperoleh dari pengukuran sifat fisik dan kimia air yaitu diperoleh rentang untuk parameter TDS dengan nilai (20-70) ppm, pH dengan rentang 6.20-8.48, dan EC dalam rentang (43-130)KataKunci : Cekungan Bandung, Gunung Malabar, Resistivitas-DC, Very Low Frequency, sifat fisik dan kimia air.

Determination Of Groundwater Recharge Area In Raimanuk And Surroundings, Timor Island

The Raimanuk area in Timor, East Nusa Tenggara, is located in the Aroki Groundwater Basin. The decreasing quality and potential groundwater availability in the Aroki Groundwater Basin is feared due to its widespread use for household needs and agriculture. The lack of the groundwater recharge area map will pose an obstacle in policymaking regarding the management and preparation of spatial conservation areas in the Raimanuk Region. This study aims to determine the zone and classification of groundwater recharge areas in the Raimanuk area based on spatial data analysis. The groundwater recharge area can be determined using slope, river flow patterns, spring emergence, and groundwater table depth. The classification of the recharge area uses a scoring approach with an overlapping analysis of the parameter assessments, which are hydraulic conductivity, precipitation, soil cover, slope, and depth of unconfined groundwater. The result of the study is the groundwater recharge area map of Raimanuk. The groundwater recharge area is located in the Mandeu Hill area, which is the main recharge area. The groundwater discharge area is located in the Aroki plain area that can be the main recharge area.

Acid Mine Drainage Sources and Impact on Groundwater at the Osarizawa Mine, Japan

Understanding the origin of acid mine drainage (AMD) in a closed mine and groundwater flow system around the mine aids in developing strategies for environmental protection and management. AMD has been continuously collected and neutralized at Osarizawa Mine, Akita Prefecture, Japan, since the mine was closed in the 1970s, to protect surrounding river water and groundwater quality. Thus, water samples were taken at the mine and surrounding groundwaters and rivers to characterize the chemical properties and environmental isotopes (δ2H and δ18O). The results showed that the quality and stable isotope ratios of AMD differed from those of groundwater/river water, indicating that the recharge areas of AMD. The recharge area of AMD was evaluated as the mountain slope at an elevation of 400–500 m while that of the surrounding groundwater was evaluated at an elevation of 350–450 m, by considering the stable isotopes ratios. This indicates that the groundwater affected by AMD is limited to the vicinity of the mine and distributed around nearby rivers.

Hydrogeology of Mangsri Cave, Gunungsewu Karst Area, Java Island, Indonesia

The Gunungsewu karst area is not only known for its unique landscape but also its recurring drought events. To meet the water supply, the local population utilizes several water potentials, namely doline pond, spring, and underground river. This study was designed to analyze the hydrogeological conditions of Mbangsri Cave, following its accidental discovery by the community at the end of 2018. The hydrogeological analysis was conducted by geological surveys, which consisted of rocks collection and structural measurements, cave mapping, and recharge area delineation based on remote sensing images acquired by unmanned aerial vehicles. The results showed that Mbangsri Cave, in the hydrogeological perspective, had low water resources potential. It is believed to be the result of (1) relatively small catchment area, (2) a fault in the southern part of Mbangsri Cave, creating a small groundwater basin, and (3) the thin epikarst layer, limiting the water storage.

Effects of Decaying Hydraulic Conductivity on the Groundwater Flow Processes in a Managed Aquifer Recharge Area in an Alluvial Fan

Groundwater artificial recharge and medium characteristics represent the major factors in controlling the groundwater flow processes in managed aquifer recharge areas. According to the depositional features of alluvial fans, an analogous homogeneous phreatic sand tank aquifer and the corresponding inhomogeneous scale numerical models were established to investigate the groundwater flow under the combined influence of artificial recharge (human activities) and decaying hydraulic conductivity (medium characteristics). In this study, groundwater flow through a managed aquifer recharge area in an alluvial fan was analyzed under the conditions of decaying hydraulic conductivity (K) with depth or length from apex to apron. The results showed that groundwater flow processes induced by artificial recharge were significantly controlled by the increasing decay exponents of K. The decaying K with depth or length in alluvial fan areas expanded the degree of influence of artificial recharge on groundwater flow. With the increase of decay exponents, the flow directions gradually changed from a horizontal to vertical direction. Groundwater age and spatial variability could also be increased by the increasing decay exponents. The residence time distributions (RTDs) of ambient groundwater and artificially recharged water exhibited logarithmic, exponential, and power law behavior. Penetration depth and travel times of ambient groundwater flow could be affected by artificial recharge and decay exponents. Furthermore, with the increase of decay exponents, the thickness of the artificially recharged water lens and travel times of artificially recharged water were increased. These findings have important implications for the performance of managed aquifer recharge in alluvial fan areas as well as the importance of considering the gradual decrease of K with depth and length.

Experimental Study on the Lateral Seepage Characteristics in the Tension Saturated Zone

To study the lateral seepage field in the tension saturated zone (TSZ), an experiment with no evaporation and precipitation infiltration was carried out in a self-made seepage tank filled up with fine sand. Based on the data and plots obtained, the lateral seepage field distribution features in the TSZ can be divided into three area for discussion: ascending area, descending area, and the nearly horizontal flow area. In the ascending and descending area, the total water potential gradient diminished from the recharge area to the discharge area and the seepage velocity was faster. In the nearly horizontal flow area, the total water potential gradient was lower and the seepage velocity was slower. The pressure potential gradually decreased horizontally from the recharge area to the discharge area, while in the vertical profile, it gradually decreased from the bottom to the top in the whole seepage area. In the absence of evaporation, the vertical water exchange among the saturated zone, TSZ, and unsaturated zone in nearly horizontal flow area is weak. Contrarily, in the ascending area and descending area, vertical water flows through both the phreatic surface and the upper interface of the TSZ. When there is lateral seepage in the TSZ, the thickness of the TSZ generally increases from the ascending area to the nearly horizontal area and then to the descending area. It should be pointed out that in the nearly horizontal area, the TSZ thickness is approximately equal to the height of the water column. Overall, the lateral seepage in the TSZ can be regarded as a stable siphon process, hence the siphon tube model can be further used to depict this lateral seepage.