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Groundwater-yielding capacity, water-rock interaction, and vulnerability assessment of typical gneissic hydrogeologic units using geoelectrohydraulic method

Akingboye Adedibu Sunny, Bery Andy Anderson, Kayode John Stephen, Ogunyele Abimbola Chris, Adeola Adedapo Oluwasanu, Omojola Olumide Olubusayo, Adesida Adeola Samuel

Acta Geophysica

2023

Vol. 71, no. 2

697--721

Geohydraulic parameters, namely hydraulic conductivity (K), transmissivity (T), effective porosity (φ), permeability (kp), anisotropy coefficient (λ), and longitudinal conductance (S), of aquifer units in Etioro-Akoko, southwestern Nigeria, were evaluated using the Schlumberger vertical electrical sounding (VES) technique. This study aimed to understand the hydrodynamics and water–rock interaction of the near-surface crustal architecture to determine the groundwater yield and vulnerability of the aquifer units in the study area. A total of 7 model curve types were generated for fifty-two geoelectrical surveyed points, with percentage distributions in the order of HA>AA>H>KH>A>HK>AK. The VES curve models constrained the subsurface layers into topsoil, weathered units, weathered/fractured bedrock units, and fresh bedrock. The weathered and fractured aquifer zones occurred at the depths of 8 m and>16 m (with depths exceeding 26.5 m for some sections). The K and T values for the aquifer units varied from 0.1901 to 0.6188 m/day and 0.7111 to 6.3525 m2/day, respectively. These parameters coupled with the aquifer φ (18.03–23.35%) and kp (0.028–0.089 µm2) classified the delineated aquifer units as low to moderate groundwater-yielding capacity aquifers, with recorded resistivity values between 85.1 Ω-m and<613.0 Ω-m. The observed positive correlations and R2 values with>32–100% prediction rates affirmed the dependence of K on T, φ, and kp for effective water–rock interactions and groundwater transmissibility. The recorded S values (0.0146–0.162 mhos) and low logarithm hydraulic resistance, Log C (0.89–1.75 years), suggested poor to weak aquifer protective capacity ratings, resulting in high aquifer vulnerability index delineated across the study area. As a result, deep-weathered/fractured aquifers should be exploited for sustainable potable groundwater supplies. However, intended wells/boreholes in the study area must be developed properly for long-term groundwater abstraction to alleviate potable groundwater deficit and optimize future operational drilling costs.

Assessment of groundwater vulnerability mapping methods for sustainable water resource management: An overview

Moges Simeneh Shiferaw, Dinka Megersa Olumana

Journal of Water and Land Development

2022

no. 52

186--198

Groundwater is a vital resource for domestic, agricultural, and industrial activities, as well as for ecosystem services. Despite this, the resource is under significant threat, due to increasing contamination from anthropogenic activities. Therefore, to ensure its reliability for present and future use, effective management of groundwater is important not only in terms of quantity (i.e. abstraction) but also quality. This can be achieved by identifying areas that are more vulnerable to contamination and by implementing protective measures. To identify the risk and delineate areas that are more exposed to pollution, various groundwater vulnerability assessment techniques have been developed across the globe. This paper presents an overview of some of the commonly used groundwater vulnerability assessment models in terms of their unique features and their application. Special emphasis is placed on statistical methods and overlay-index techniques. The assessment of the literature shows that statistical methods are limited in application to the assessment of groundwater vulnerability to pollution because they rely heavily on the availability of sufficient and quality data. However, in areas where extensive monitoring data are available, these methods estimate groundwater vulnerability more realistically in quantitative terms. Many works of research indicate that index-overlay methods are used extensively and frequently in groundwater vulnerability assessments. Due to the qualitative nature of these models, however, they are still subject to modification. This study offers an overview of a selection of relevant groundwater vulnerability assessment techniques under a specific set of hydro-climatic and hydrogeological conditions.

Ocena zależności stężeń wybranych wskaźników fizyczno-chemicznych w wodach podziemnych Polski od formy użytkowania terenu na podstawie wyników badań monitoringowych

Razowska-Jaworek Lidia, Kowalczyk Agnieszka, Kuczyńska Anna, Palak-Mazur Dorota, Mikołajczyk Anna

Biuletyn Państwowego Instytutu Geologicznego

2019

nr 476, Hydrogeologia z. 17

105--113

W celu oceny wpływu działalności człowieka na wody podziemne, analizie poddano skład chemiczny wód podziemnych występujących na obszarach o różnorodnych sposobach użytkowania terenu. Do badań wykorzystano wyniki analiz fizyczno-chemicznych wód podziemnych wykonywanych w ramach monitoringu krajowego w latach 1995–2017, w podziale na różne stopnie izolacji opróbowanych poziomów wodonośnych. Najbardziej są zanieczyszczone wody pochodzące z otworów monitoringowych zlokalizowanych na obszarach przemysłowych w poziomach o swobodnym zwierciadle wody. W wodach pobranych z punktów monitoringowych zlokalizowanych na obszarach wiejskich oraz na obszarach występowania gruntów ornych stwierdzono wysokie zawartości azotanów i siarczanów, a na obszarach miejskich podwyższone są także stężenia fosforanów i cynku. Najmniej zanieczyszczone są wody z punktów monitoringowych umiejscowionych na terenach zieleni miejskiej. Chemizm wód podziemnych w analizowanych punktach monitoringowych zależy zarówno od czynników naturalnych, jak i charakteru użytkowania terenu. Podwyższone stężenia NO3 –, HPO4 – lub SO4 2– są ewidentnie wynikiem działalności człowieka, podczas gdy podwyższone stężenia Na, Cl i NH4 + mogą być zarówno pochodzenia antropogenicznego, jak i skutkiem naturalnych procesów hydrogeochemicznych. Stężenia Ca i Mg w badanych wodach podziemnych są głównie efektem procesów naturalnych.

The chemical quality of groundwater beneath the different types of land use areas was examined to evaluate the effects of human activities on groundwater. The study of the results of groundwater quality tests conducted as part of the Polish National Monitoring in 1995–2017 was performed in order to evaluate the effects of human activities on groundwater in the aquifers of different levels of isolation. The most polluted waters are those collected at monitoring points located within unconfined aquifers of industrial areas. The waters taken from monitoring points located in rural areas and arable lands show a high level of nitrates and sulphates. In urban areas, also phosphate and zinc concentrations are elevated. The least polluted waters were collected from points located in urban green areas. The groundwater chemistry in analyzed monitoring points depends on both natural factors and the nature of land use. Elevated concentrations of NO3 –, HPO4 – or SO4 2– are evidently the result of human activity, while the increased levels of Na, Cl and NH4 + come from both anthropogenic sources and natural processes. Ca and Mg concentrations in the studied waters are mainly the result of natural processes.