Groundwater level oscillation analysis in shallow alluvial aquifers in Pomurje, NE Slovenia

Systematic hydrologic monitoring of groundwater quantity at the national level in Slovenia has been ongoing since 1952. An insight into long-term groundwater level data enables us to delineate parts of aquifers with similar groundwater level oscillation properties as well as to identify changes of those properties in time. We used variety of statistical methods to identify long-term behaviour of groundwater level oscillation of groundwater body (GWB) Murska kotlina. Results showed that fluctuation of groundwater level in time reflect complex set of events that originate in natural or anthropogenic interferences. Using percentile analysis in combination with cluster analysis, we were able to isolate areas with a related groundwater fluctuation. Results of long-term data trends analyses of monthly groundwater level showed the impact of the research area climate on long-term and seasonal groundwater level fluctuation. In addition to natural causes, by performing trend analysis on groundwater level data, we were able identify some human induced interventions into the environment made in the past.

Tectonic Structure and Relationship with Sinkhole Harzard in Bang Lung Area, Cho Don District, Bac Kan Province

By integration of remote sensing images analysis, geology, geomorphology, hydrogeology, geophysical method, and drilling data, the paper illustrates the structure tectonics, causes, and initial mechanism of a sinkhole forming in Bang Lung, Cho Don, Bac Kan province. The NE-SW normal slip faults are an essential fault system in the area, which created Bang Lung graben valley. This fault system also forms large fracture zones, creating advantage conditions for the groundwater runoff both vertically and horizontally to eroded and dissolved carbonate rock-forming underground karst caves. These are favorable natural conditions for forming a sinkhole. The sinkhole hazard in the Bang Lung area is initiated by some main factors such as tectonic activity, thickness, and characteristics of unconsolidated sediment layers, groundwater fluctuation, karst caves, and human activities. The most human impacts are mining exploitation and agricultural cultivation that promote sinkholes occurring faster and earlier. The horizontal and vertical movement of groundwater dragged the material on the ceiling karst caves into ground spaces. Thereby, weakening the cohesion of the unconsolidated sediment above caves leads to gravitational unbalance and creates a sinkhole. This study has also shown potential sinkhole areas in Bang Lung, which helps the authorities and local people in sinkhole prevention and mitigation mission.

GRNN Model for prediction of groundwater fluctuation in the state of Uttarakhand of India using GRACE data under limited bore well data

Springs, the primary source of water in the Indian state of Uttarakhand, are disappearing day by day. A report published by United Nations Development Program in 2015 indicates that due to deforestation, and forest fire, the groundwater of the state has been reduced by 50% between 2007 and 2010. As such, for taking proper adaptation policies for the state, it is necessary to monitor the state's groundwater fluctuation. Unfortunately, the bore well data are very limited. Thus, we are proposing two general regression neural network (GRNN)-based models for fast estimation of groundwater fluctuation. The first model evaluates and predicts the groundwater fluctuation in the five known bore well data districts of the state, and the second model, which is based on the first model along with a correlation matrix, predicts the groundwater fluctuation in the districts where no bore well data are available. The assessment of the results shows that the proposed GRNN-based model is capable of estimating the groundwater fluctuation both in the areas where bore well data are available and the areas where bore well data are not available. The study shows that there is a sharp decline in the groundwater level in the hilly districts of the state.

Tingkat Fluktuasi Air Tanah pada Jangka Pendek di Kecamatan Ngemplak, Kabupaten Sleman, Provinsi Daerah Istimewa Yogyakarta

ABSTRACT Water is a natural resource used by people for various life necessities. The type of water often used by people is groundwater. Groundwater conditions should be inventoried to protect and maintain the continued function of groundwater. The research area was the administrative area of the Ngemplak Sub-district in Sleman Regency. Construction, growing population, and changing system positively correlate with potential disturbance to quantity, quality, and distribution of groundwater in the research area. To anticipate this, changing groundwater conditions in the administrative area of the Ngemplak Sub-district should be determined. The present study was aimed to determine the changing condition or dynamics of groundwater in the administrative area of Ngemplak Sub-district. The parameter used in the present study was the level of groundwater fluctuation. The primary data of groundwater depth in rainy and dry seasons 2019 was collected using a systematic random sampling method. Groundwater surface fluctuation data was obtained from the difference in groundwater-surface depths in dry and rainy seasons. The level of groundwater fluctuation was analyzed using the spatial interpolation method and classified using ArcGIS. The research result showed that the level of groundwater fluctuation in the research area consisted of three classes, i.e., low (<2.5 meters), medium (2.5 – 5 meters), and high (>5 meters). The research area was dominated by medium groundwater fluctuation. Spatial data analysis showed that groundwater fluctuation in the research area wasn’t only affected by reduced groundwater supply due to changing seasons but also by the massive groundwater usage. Keywords: groundwater, fluctuation, spatial interpolation ABSTRAK Air merupakan sumberdaya alam yang digunakan penduduk untuk memenuhi beragam kebutuhan hidup. Jenis air yang seringkali digunakan penduduk adalah air tanah. Inventarisasi kondisi air tanah perlu dilakukan sebagai upaya untuk menjaga dan mempertahankan keberlanjutan fungsi air tanah. Wilayah yang menjadi perhatian dalam penelitian ini adalah wilayah Kecamatan Ngemplak, Kabupaten Sleman. Pembangunan, peningkatan jumlah penduduk, dan peralihan musim berkorelasi positif dengan munculnya potensi gangguan terhadap kuantitas, kualitas, dan distribusi air tanah di daerah penelitian. Untuk mengantisipasi hal tersebut maka perubahan kondisi air tanah di wilayah Kecamatan Ngemplak perlu diketahui. Penelitian ini bertujuan untuk mengetahui perubahan kondisi atau dinamika air tanah di wilayah administratif Kecamatan Ngemplak. Parameter yang digunakan dalam penelitian ini adalah tingkat fluktuasi air tanah. Data primer kedalaman air tanah pada musim hujan dan kemarau tahun 2019 dikumpulkan dengan metode systematic random sampling. Data fluktuasi air tanah merupakan selisih dari kedalaman air tanah pada musim kemarau dengan musim hujan. Tingkat fluktuasi air tanah dianalisis menggunakan metode interpolasi spasial dan klasifikasi dengan perangkat lunak ArcGIS. Hasil penelitian menunjukkan bahwa tingkat fluktuasi air tanah di daerah penelitian diklasifikasikan menjadi tiga kelas, yaitu rendah (<2,5 meter), sedang (2,5 – 5 meter), dan tinggi (>5 meter). Daerah penelitian didominasi oleh fluktuasi air tanah pada tingkat sedang. Analisis data spasial menunjukkan bahwa fluktuasi air tanah di daerah penelitian tidak hanya dipengaruhi berkurangnya suplai air tanah akibat perubahan musim, tetapi juga diakibatkan penggunaan air tanah dalam jumlah yang besar. Kata kunci: air tanah, fluktuasi, interpolasi spasial

Time Variations of the Vertical Component in Some of Japanese GEONET GNSS Sites

We analyze the vertical component of GEONET GNSS measurements in Central Japan and clarify in some of the sites the origin of large annual time variations, as well as the secular variations. Many of these vertical movements may be attributable to the use of groundwater for agriculture, for snow melting, industrial, and hospital usages, etc. and the pumping up of the groundwater mining for refining natural gas and iodine at the production area of natural gas dissolved in water. For this reason, highly accurate monitoring of vertical variations by GNSS observations can provide new observation methods for understanding of not only geodynamics but also hydrology through monitoring groundwater fluctuation, and natural gas and oil resource development through monitoring ground movements caused by mining.