Bencana Kekeringan di Wilayah Taman Bumi Nasional Karangsambung-Karangbolong: Pengontrol, Dampak, dan Ketahanan

ABSTRAKKaranggayam dan Karangsambung di Kabupaten Kebumen termasuk ke dalam zona bahaya tinggi terdampak bencana kekeringan. Kedua daerah tersebut memiliki variasi batuan yang lengkap mulai dari batuan beku, batuan sedimen, hingga batuan metamorf, dan termasuk ke dalam wilayah Taman Bumi Nasional Karangsambung-Karangbolong. Prediksi dan penentuan area yang masih memiliki cadangan air tanah menjadi hal yang vital untuk segera dilakukan guna mengurangi dampak dari bencana tersebut, ditunjang dengan pengetahuan mengenai pengontrol utama dari parameter penyebab bencana kekeringan di daerah Karanggayam dan Karangsambung. Observasi lapangan dan analisis geospasial dipilih menjadi metode karena dinilai lebih efisien untuk penelitian ini, serta didukung dengan hasil analisis statistik dari data sekunder. Fisiognomi tanah, kondisi geologi, dan angka infiltrasi yang merupakan bagian dari delapan karakteristik geografi dan geomorfologi, dinilai menjadi pengontrol utama dari parameter penyebab bencana kekeringan yang terjadi di Karanggayam dan Karangsambung. Ketiga karakteristik tersebut berperan dalam mempersempit kemungkinan area cadangan air tanah menjadi hanya berada di sekitar lembah antiklin dan lereng sayap antiklin bagian selatan-tenggara (S-SE). Seluruh hasil penelitian ini dapat berfungsi untuk membantu pemerintah daerah dan pengelola taman bumi dalam membuat berbagai macam perencanaan dan kebijakan terkait Taman Bumi Nasional Karangsambung-Karangbolong.Kata kunci: bencana, cadangan air tanah, Kebumen, kekeringan, taman bumiABSTRACTKaranggayam and Karangsambung in Kebumen Regency included in the high danger zone affected by drought. Both areas have complete rock variations ranging from igneous, sedimentary, to metamorphic rocks, and are included in the Karangsambung-Karangbolong National Geopark. Prediction and determination of areas that still have groundwater reserves are vital to be carried out immediately to reduce the disaster’s impact, supported by the knowledge of the main controllers of drought-causing parameters in both areas. Field observations and geospatial analysis were chosen because they were considered more efficient and supported by the results of statistical analysis from secondary data. Soil physiognomy, geological conditions, and infiltration rates are considered the main controllers causing drought disasters in Karanggayam and Karangsambung areas. These three characteristics narrow down the possibility that the groundwater reserve area is only around the anticline valley and the south-southeast (S-SE) side of the anticline wing. All of the results of this study can help local governments and geopark management to make various plans and policies related to the Karangsambung-Karangbolong National Geopark.Keywords: disaster, groundwater reserves, Kebumen, drought, geopark

Determine the exploitable groundwater reserve of Con Son Island in the condition of climate change and sea level rising

The paper deals with problem of groundwater sustainable exploitation in accordance with the allowable drawdown, stipulated in Circular 27/2014/TT-BTNMT of Ministry of Natural Resources and Environment in combination with the sustainablity index, advised by UNESCO. The technical method is using a groundwater model containing reliable input data. As a result, a groundwater flow model was successfully constructed for stimulating the actual groundwater system in Con Son Island. The model was calibrated, using groundwater monitoring data of 12 wells and produced an error less than ±0.5m. On the basis of the current model, a prediction was made under condition of climate change and sea level rise up to the scenario RCP 4.5. Based on this prediction, the exploitable groundwater reserve of Con Son island was calculated as 14.430m3/day.

Groundwater reserve and capacity of groundwater extraction for Ilmenite placer mining in Ninh Thuan province

Mining ilmenite placer develops quickly along the coastal zone in the center area, Vietnam. In Ninh Thuan province, the mines are mostly using water for the exploitation. We simulated groundwater flow with uncertain parameters in order to answer if groundwater can supply a part of water demand for the exploitation of ilmenite by using GMS software. Unfortunately, as the results of simulation, groundwater is not enough to supply for ilmenite exploitation. The authors calculated the ilmenite reserves in several communes in Ninh Thuan and water demands. Comparison of water demands and ability of groundwater supply concludes that local government should make a sustainable strategy of water use to preserve groundwater.

Assessment of Economically Accessible Groundwater Reserve and Its Protective Capacity in Eastern Obolo Local Government Area of Akwa Ibom State, Nigeria, Using Electrical Resistivity Method

The application of geophysical method employing vertical electrical sounding (VES) method in combination with laboratory analysis of aquifer sediments has been used to access the economically accessible groundwater reserve and its protective capacity in some parts of Eastern Obolo Local Government area, the eastern region of the Nigerian Niger Delta. Schlumberger electrode configuration was used to sound twelve VES to occupy the areas that have borehole locations and accessibility for the spread of current electrodes to at least 1000 m. Based on the results, the safe and economic aquifer potential has groundwater reserve of about 168480558±18532861 m3. The desired aquifer thickness and its depth of burial have average value of 52.02 m and 73.14 m, respectively. The area has a fair protective capacity. This is indicated by 58.33% weak, 16.67% moderate, and 25% good protective capacity for the area. This study was done in one of the oil cities, where contaminated Salt River water is used as the major source of water for domestic uses and it is believed that the settlers will appropriate this result and sue for safe groundwater at the indicated depths.