Submarine groundwater discharge (SGD) from tropical volcanic islands locally transports significant amounts of terrestrial nutrients into the coastal ocean, which can affect sensitive coastal ecosystems such as coral reefs. In northwestern Lombok, terrestrial submarine groundwater discharges through several submarine springs at the seafloor into a coral reef. In order to understand the transport mechanisms of nutrients from land into the reef, we investigated nutrient fluxes via SGD within the area using a combination of different methods, including recharge estimates in the coastal catchment area, echosounder profiling of the seafloor, discharge measurements, and hydrochemical analyses (stable isotopes of water, radon, and nutrients). Different types of springs can be distinguished based on their morphology. One spring showed a “crater”‐shaped structure while other springs consisted of fissures. Recharge rates in the coastal catchment amounted to 5 L s−1, while discharge rates from the largest spring were 5 L s−1 for total SGD and 2.5 L s−1 for fresh SGD, which is similar to discharge rates from smaller onshore springs at the slopes of a volcano. SGD was in general a source of nutrients such as dissolved silicon (~ 226 mol d−1), phosphate (0.61 mol d−1), or total dissolved nitrogen (13.4 mol d−1). Nitrate concentrations varied among the different springs, probably due to different sources in the hinterland, transformations (e.g., denitrification), or biological uptake during transport from land into the ocean. As nitrate can considerably affect coral reef health, our findings suggest that especially nitrate should be monitored around submarine springs in Indonesia.
Airtanah saat ini telah menjadi isu di dunia dan Indonesia akibat terjadinya degradasi airtanah. Tingginya pertumbuhan penduduk dan industri di wilayah kota telah meningkatkan eksploitasi airtanah, sementara laju pengisian airtanah (infiltrasi) terus menurun. Penurunan laju infiltrasi diakibatkan oleh adanya perubahan tutupan lahan. Berdasarkan permasalahan ini maka konservasi airtanah harus dilakukan untuk menjaga ketahanan air. Cekungan Bandung-Soreang sebagai wilayah perkotaan telah mengalami penurunan muka airtanah sebagai akibat adanya pengambilan airtanah yang berlebih. Tulisan ini adalah telaah dari berbagai metode teknis yang telah diterapkan untuk mengatasi masalah tersebut di atas khususnya metode imbuhan buatan untuk konservasi airtanah di Cekungan Bandung. Berbagai teknik telah diterapkan baik oleh masyarakat, industri maupun pemerintah dengan sumber utama adalah air hujan. Namun penurunan muka airtanah masih terus terjadi meskipun upaya-upaya tersebut telah dilakukan. Hasil penelitian terakhir menunjukkan bahwa metode imbuhan buatan hanya mampu mengurangi penurunan muka airtanah. Jika hasil yang diharapkan adalah kembalinya muka airtanah ke kondisi awal maka diperlukan pengembangan metode dan atau penambahan jumlah imbuhan buatan yang sangat banyak. Groundwater becomes an issue globally due to groundwater degradation. The high population and industry growth in the cities had increased the exploitation of groundwater. On the other hand, the rate of infiltration is lower due to city development. Therefore, groundwater conservation is required to maintain water resistance. The Bandung-Soreang Basin, as an urban area, has experienced a decline in groundwater as a result of excessive groundwater extraction. This paper presented a review of various technical methods that have been applied to overcome the problem. Artificial recharge method for groundwater conservation in the Bandung-Soreang Basin has been used by the community, industry, and government, with rainwater as the main source. The most recent condition indicated that the groundwater level has been still decreasing despite these efforts. The results of the latest research suggested that artificial recharge has only reduced the groundwater depletion. To restore the groundwater to its initial condition, we need to develop a new method or simply add a lot more artificial recharges.
Desa Ligarmukti di Kabupaten Bogor merupakan kawasan perbukitan karst yang kaya sumber mata air sehingga mampu memasok kebutuhan air untuk keperluan domestik maupun pertanian. Sifat hidrokimia yang berasal dari batuan gamping memiliki karakter tersendiri yang dapat saja berdampak pada kualitas hasil pertanian. Sehubungan dengan hal tersebut, penelitian ini dilakukan untuk menganalisis hidrokimia mata air karst untuk irigasi. Metode penelitian yang dilakukan yaitu inventarisasi data sekunder, pengamatan hidrogeologi, dan analisis laboratorium. Sodong adalah mata air terbesar dengan debit 314,42 l/s pada musim hujan dan 154,38 l/s pada musim kemarau. Luas lahan persawahan kurang lebih 300 ha. Debit mata air tersebut dapat mengaliri sawah seluas 314,14 ha pada musim hujan dan 154,38 ha pada musim kemarau. Selain debit, faktor hidrokimia juga menentukan hasil pertanian. Hidrokimia air tanah termasuk fasies Ca-HCO3, sistem aliran air tanah dikontrol oleh autogenic recharge yang menunjukkan jenis air pada mata air berasal dari air hujan secara langsung terinfiltrasi pada daerah tersebut. Klasifikasi air untuk irigasi termasuk tipe C2-S1 yang menunjukkan mata air memiliki kualitas air tanah yang baik, risiko salinitas menengah dan risiko sodium yang rendah. Hasil penelitian ini dapat menjadi masukan pada pemerintah untuk mempertahankan Desa Ligarmukti sebagai lumbung pertanian.
In 2015, the number of international tourists who visited Borobudur temple declined and did not reach the government target. It was because there was only one attraction in the temple. After visiting Borobudur, most of tourists move to another place such as Yogyakarta. They know about the temple, but not its past environment when the temple was built. The history and past environment of Borobudur temple could be developed as additional tourist attractions to make them stay longer in that area. Geological condition and the evidences of an ancient lake could be developed as tourist objects. It is very interesting and could be developed to educate visitors in geo-archeology. The aim of this research is to develop archeological (temple) tourism based on geology and past environment. Although many researches on geo-archeology have been done, the results which relate to tourism are still not widely applied yet. The methods used are secondary data analysis and a field survey to investigate the potential of tourist stop sites. The potential tourist attractions were determined by geomorphology, lithology outcrops, stratigraphy, environment, and accessibility. The result is ten stop sites which could be used to describe the paleoenvironment in Borobudur based on geosciences. These tourist objects could explain the environment in the past related to the temple reliefs and ancient human activities.
Abstract. This paper is to review how to investigate the interactions between groundwater and seawater. Those interactions divide into two, which are submarine groundwater discharge and seawater intrusion. This investigation is important because the interactions can give impact to coastal aquifer and marine ecosystem. On land, fresh groundwater is vulnerable to seawater disturbance. Coastal aquifer is under pressure from abstraction caused by population, industry, and agriculture. The pumping can induce seawater intrusion and land subsidence. Then in marine, seawater mixes with freshwater and it decreases salinity. Low salinity will influence marine ecosystem. The ecosystem will be disturbed by groundwater discharge if that water is contaminated. Based on the argue investigation of groundwater-seawater interactions is important and must be accurate because the results are used for coastal water management. To investigate the interactions data, i.e., lithology, pumping tests, hydrochemical data, sea level rise estimates, precipitation data, geophysics, environmental isotopes, and drilling information, should be compiled. The interaction can feed a model to determine how much groundwater extraction happening on coastal areas to prevent seawater intrusion and land subsidence. Water resources management on coasts should consider groundwater-seawater interactions.
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