Mapping Interflow Potential and the Validation of Index-Overlay Weightings by Using Coupled Surface Water and Groundwater Flow Model

Interflow is an important water source contributing to river flow. It directly influences the near-surface water cycles for water resource management. This study focuses on assessing the interflow potential and quantifying the interflow in the downstream area along the Kaoping River in southern Taiwan. The interflow potential is first determined based on the modified index-overlay model, which employs the analytical hierarchy process (AHP) to calculate the ratings and weightings of the selected factors. The groundwater and surface water flow (GSFLOW) numerical model is then used to link the index-overlay model to quantify the interflow potential for practical applications. This study uses the Monte Carlo simulations to assess the influence of rainfall-induced variations on the interflow uncertainty in the study area. Results show that the high potential interflow zones are located in the high to middle elevation regions along the Kaoping River. Numerical simulations of the GSFLOW model show an interflow variation pattern that is similar to the interflow potential results obtained from the index-overlay model. The average interflow rates are approximately 3.5 × 104 (m3/d) in the high elevation zones and 2.0 × 104 (m3/d) near the coastal zones. The rainfall uncertainty strongly influences interflow rates in the wet seasons, especially the peaks of the storms or heavy rainfall events. Interflow rates are relatively stable in the dry seasons, indicating that interflow is a reliable water resource in the study area.

Assessing Specific Vulnerability of Shallow Aquifers to Pesticide Using GIS Tools. Data Needs and Reliability of Index-Overlay Methods: An Application to the San Giuliano Terme Agricultural Area (Pisa, Italy)

Pesticides play a crucial role in regulating crop production by reducing crop losses and increasing crop yield and quality. However, they may threaten surface and groundwater, a phenomenon occurring at global scale, potentially causing environmental damage and prohibition of water use or high treatment costs for drinking water. Assessing spatially-defined aquifer vulnerability to pesticide is then important, as it may allow defining agricultural areas where pesticides should be used following well-defined agronomic practices/limitations. In this study, after a brief review of recent studies on aquifer vulnerability assessment to pesticide, we applied the Vulnerability Index method to the agricultural area of the Municipality of San Giuliano Terme (Pisa, Italy) in order to focus on the data needs and discuss the reliability of this method (as an example of index-overlay methods). The proposed method needs a relatively small number of parameters compared to other more complex ones. Despite a such a small number of parameters, some were not easily available in our case study. Thus, some assumptions were made. This led to vulnerability maps with reduced reliability, no validation with groundwater samples, and little practical use. This means that to produce robust but static vulnerability assessments, large datasets are needed. In turn, the cost of data gathering may be high. The value of these data may, however, be increased, and the cost better justified if the analyses are based on process-based or advanced statistical methods. While the future for vulnerability assessment methods is the use of process-based/advanced statistical methods, index-overlay methods, as a preliminary step for process-based simulation analysis, may still provide initial and relatively quick insights on potential leaching of pesticides. This in turn may support extension services in delivering timely and relevant advices on the use of such pesticides to farmers and owners of plant nurseries and greenhouses.

Analisis Index Overlay Untuk Pemetaan Kawasan Berpotensi Banjir di Gowa, Provinsi Sulawesi Selatan

Pada awal tahun 2019 Kabupaten Gowa dilanda bencana banjir yang menelan korban jiwa, akibat dari hujan dengan intensitas tinggi yang terus melanda kabupaten ini. Berdasarkan hal tersebut maka penelitian ini dilakukan dengan tujuan untuk mengetahui kawasan rawan banjir pada Kabupaten Gowa, Provinsi Sulawesi Selatan dan mengantisipasi dampak dari bencana banjir, baik untuk respons darurat, pemulihan setelah bencana, penetapan strategi untuk mitigasi bencana, serta perancangan penggunaan lahan yang dapat menyimpan air dan menggabungkannya dengan pembangunan berkelanjutan. Dalam penentuan parameter banjir digunakan metode Analisis Weighted Scorring pada Data curah hujan rata-rata bulanan tahun 2012-2019, DEM SRTM wilayah Kabupaten Gowa, Provinsi Sulawesi Selatan, dan peta wilayah Kabupaten Gowa, Provinsi Sulawesi Selatan, yang kemudian dapat digunakan untuk menghitung, mengetahui dan menentukan tingkatan serta parameter-parameter kerentanan banjir serta dapat dilakukan analisis untuk menentukan tingkat kerawanan banjir yang menghasilkan model klasifikasi tingkat kerawanan banjir. Sehingga akan dihasilkan peta mengenai potensi bencana banjir pada wilayah penelitian. Di mana hasil dari penelitian ini menunjukkan bahwa daerah Gowa memiliki kelas lereng datar, dengan kelas drainase buruk- sangat buruk, kemudian tutupan lahan merupakan sawah dan juga pemukiman dengan curah hujan tahunan sebesar 2000-2900 mm/thn.

USING INDEX AND CUMULATIVE OVERLAY ANALYSES TO DETERMINE GEOTHERMAL POTENTIAL TARGETS IN DAMAVAND REGION

The Damavand region is located in the north of Iran and north-eastern of Tehran. In the present study, geothermal favorability map in this region has been prepared using two methods of data integration in the geographic information system (GIS) environment. The purpose of this study is to introduce the areas with high potential of geothermal field in Damavand region for subsequent exploratory program. For this purpose, at first, necessary information layers identified and studied and then were processed. The 13 layers were identified and collected and integration with two cumulative and weighted index overlay methods and compared. After a survey of experts, the weights used in the weighted index overlay method were obtained from the Fuzzy /Ahp method. In the result of cumulative overlay method, south and southeast of Damavand volcano are favorable area for geothermal field but the result of the weighted index overlay method indicates the high potential of the southeastern region of Damavand. Comparing the results with gradient and thermal flux from drilling by the ENEL Italian Company, indicate the accuracy and precision of the obtained results.

RECOGNITION OF GOLD MINERALIZATION FAVORABILITY ZONES THROUGH AIRBORNE GAMMA-RAY SPECTROMETRY AND MAGNETOMETRY IN BRUSQUE AND BOTUVERÁ REGION, SOUTHERN BRAZIL

ABSTRACT. The northeastern portion of Santa Catarina State, southern Brazil, bears important primary gold mineralization associated with granitic intrusions with potassic and phyllic hydrothermal alteration zones and a phase shear zone reactivation. Airborne radiometric and magnetic data were applied in the study area through the use of gamma-ray spectrometry (Total Count, K, eTh and eU) and suggestive parameters of hydrothermal alteration as Kd, Ud and F, in association with geological units, while magnetometry (RTP, THDR, TDR and Signum Transform) was applied in the definition of the structural framework. Geophysical data was interpreted and integrated to geological information, such as lithologic units, structures, shear zones and gold mineralization, using the knowledge driven and index overlay methods in order to define favorable targets. The geophysical and geological data exhibit good correlation, as seen in the gamma-ray spectrometric domains and magnetic lineaments, and the favorability map shows important target areas for primary gold mineralization. It was possible to observe in the geophysical maps that shear zones and faults have more influence in the occurrences than potassic and phyllic hydrothermal alteration related to granitic intrusions.Keywords: geophysical exploration, knowledge-driven, Dom Feliciano Belt.RESUMO. A porção nordeste do estado de Santa Catarina, sul do Brasil, possui importantes mineralizações auríferas primárias associadas a intrusões graníticas com zonas de alteração hidrotermal potássica e fílica e posterior fase de reativação de zonas de cisalhamento. Dados radiométricos e magnéticos aerogeofísicos foram aplicados na área de estudo através do uso de gamaespectrometria (Contagem Total, K, eTh e eU) e parâmetros sugestivos de alteração hidrotermal como Kd, Ud e Parâmetro F. Em associação com unidades geológicas, enquanto a magnetometria (RTP, GHT, ISA e Signum Transform) foi aplicada na definição do arcabouço estrutural. Os dados geofísicos foram interpretados e integrados às informações geológicas, como unidades litológicas, estruturas, zonas de cisalhamento e mineralizações de ouro, utilizando os métodos knowledge-driven e index overlay para definir alvos favoráveis. Os dados geofísicos e geológicos apresentam boa correlação, como visto nos domínios espectrométricos de raios gama e lineamentos magnéticos, e o mapa de favorabilidade mostra áreas-alvo importantes para a mineralização de ouro primária. Foi possível observar nos mapas geofísicos que as zonas de cisalhamento e as falhas têm mais influência nas ocorrências do que as zonas de alteração hidrotermal potássica e fílica relacionada às intrusões graníticas.Palavras-chave: exploração geofísica, knowledge-driven, Cinturão Dom Feliciano.