Achille Basile Anaba Onana

Assessment of groundwater rise zones using electrical resistivity for foundation stability analysis

Serge Parfait Koah Na Lebogo, Philémon Zo’o Zame, Achille Basile Anaba Onana, Franck Stell Kameni, Harold Gwet, Dieudonné Bisso

Discover Geoscience

Poor drainage conditions can lead to soil erosion and water infiltration, potentially compromising the stability of nearby buildings. This study aims to identify and characterize zones of rising groundwater at a construction site in southeastern Bangui, Central African Republic. The objective is to evaluate the potential impact of these zones on foundation stability and to guide the design of effective drainage systems. Electrical resistivity tomography (ERT) was employed as the primary investigative method, using a Schlumberger array with 2-meter electrode spacing. This geophysical technique was selected due to its proven effectiveness in delineating subsurface structures and assessing groundwater flow patterns in complex geological settings. The ERT survey revealed three distinct layers: (i) weathered bedrock (236–750 Ω·m); (ii) fissured bedrock (750–2,400 Ω·m); and (iii) fresh bedrock (> 2,400 Ω·m). Zones of low resistivity (less than 236 Ω·m) indicated saturated areas likely associated with groundwater accumulation. Two aquifer systems were identified: a shallow weathered bedrock aquifer (2–4 m deep) and a deeper fissured aquifer. The shallow aquifers extend laterally 3–10 m, with a water table depth of 1.5–3 m. They lack hydraulic connectivity with the deeper system, which likely contributes to the observed rise in groundwater levels. These findings underscore the importance of detailed hydrogeophysical surveys in construction planning. Rising groundwater, resulting from isolated aquifer systems, can threaten the structural integrity of foundations. The results inform the design of more resilient drainage infrastructure and highlight the need for ongoing hydrogeological monitoring, particularly of piezometric levels and flow dynamics, to ensure the site’s long-term . ✓ Electrical resistivity tomography reveals hidden groundwater risks at construction sites. ✓ Two disconnected aquifers can contribute to rising groundwater levels, which can impact the stability of infrastructure. ✓ A multi-layered aquifer system influences drainage system design and soil behavior.

• #geophysical and geoelectrical methods
• #geophysical methods and applications
• #seismic waves and analysis
• #foundation (evidence)

Hydrochemistry and Water Quality Index for Sustainable Drinking Water and Irrigation Management of Mbankomo (Center, Cameroon)

Achille Onana, Achille Onana, Derrick Kengmo, Alix Onana, Achille Basile Anaba Onana, Jules Rémy Ndam Ngoupayou

Hydrology

Hydrochemistry is the study of chemical properties and processes that occur in water, including the interactions between water and the surrounding environment. To understanding the chemical composition of water and assess their suitability for drinking and irrigation purpose, water samples were collected of Mbankomo at 10 locations during rainy seasons. From theses samples, anions and cations were separated by high performance liquid chromatography (HPLC) using a Dionex ICS-1100 with 0.45 µm diameter. From de findings, it is clear that surface water has an average pH of 5.63 while, groundwater has an arithmetic mean pH of 5.94, with a range between 5.00 and 6.64. These data indicates that the water remains acidic. From the values of TDS (Total Dissolved Solid) (average value of 26.65 mg/l. in surface water; 27.30 to 118.38 mg/l, in groundwater) water samples in the study area are considered fresh (TDS < 1000 mg/l). Water in the research area acquires mineralization through a variety of natural geochemical processes, such as weathering, dissolution, ion exchange processes, and human activity. WQI (Water Quality Index), based on 14 major parameters indicate that water of study area are good to excellent and can use for drinking, irrigation and industry. The water of study area is suitable for irrigation for almost all types of crops with a possibility of limited sodium hazards.

• #water quality and pollution assessment
• #groundwater and isotope geochemistry
• #groundwater and watershed analysis
• #water quality

Water quality and human health risk assessment of nitrate in the SAO watershed (West, Cameroon)

Achille Basile Anaba Onana, Steve Yannick Ngassam, Zakari Mfonka, Alix Audrey Nga Onana, Jules Rémy Ndam Ngoupayou

Discover Geoscience

Water is a vital resource for food, agricultural and electrification needs. These needs, combined with population growth and water availability issues, contribute to the high demand for this natural resource, with the corollary of anthropogenic pollution, which degrades its quality. In this context, the present work aims to characterize water quality and assess its suitability for drinking and agricultural purposes using various indices. A total of 25 surface and groundwater samples were collected from the study area. These samples were subsequently analyzed using the HPLC ion chromatography method on a Dionex ICS-1100 to determine chemical parameters, including pH, TDS, Ca2+, Mg2+, Na+, K+, Cl–, SO42−, HCO3–, and NO3–. The pH levels are sometimes acidic and sometimes basic, which is not suitable for human consumption and exceeds the WHO standard. The order of dominant ions is Na+ > Ca2+ > Mg2+ > K+ > NH4+ and NO3− > Cl− > SO42− > F− > HCO3− > PO43−. Water in the research area acquires mineralization through a variety of natural geochemical processes, such as weathering, dissolution, ion exchange processes, and human activity. PCA and various ion ratios reveal that water mineralization is characteristic of anthropogenic impacts and biogeochemical processes. The pollution index indicates that the entire study area is subject to pollution. Nitrate pollution indices reveal that the water sample tests are unsuitable and can cause methemoglobinemia or blue baby syndrome. The water of the study area is suitable for irrigation for almost all types of crops, with a possibility of limited sodium hazards.

• #groundwater and isotope geochemistry
• #water quality and pollution assessment
• #watershed
• #water quality

Finding parameter that provide higher boreholes flow rate: using ANOVA test, Cameroon

Achille Basile Anaba Onana, Olive Nathalie Kouamen Njikeu, R. M. Onana Onana

Sustainable Water Resources Management

• #drilling and well engineering
• #hydraulic fracturing and reservoir analysis
• #groundwater flow and contamination studies
• #lineament

Analysis of crystalline bedrock aquifer productivity: Case of central region in Cameroon

Achille Basile Anaba Onana, Jules Rémy Ndam Ngoupayou, Joseph Mvondo Ondoa

Groundwater for Sustainable Development

• #groundwater flow and contamination studies
• #groundwater and watershed analysis
• #groundwater and isotope geochemistry
• #bedrock

The Risk of Adverse Maternal and Neonatal Outcomes in Cameroonian Primiparous Women Aged More Than 26 Years

Elie Nkwabong, Joseph Nelson Fomulu, A.M. Ben Hamida, Achille Basile Anaba Onana, Paul Tjek, L Kouam and 1 more

clinics in Mother and Child Health

Primiparas with advanced age are predisposed to adverse maternal and neonatal risks. The aim of this retrospective cohort study, conducted between January 1st and December 31st, 2004 in the maternity of the Yaounde University Teaching Hospital, Cameroon, was to identify from what age these adverse risks become significant in Cameroonian women. The medical files of 233 primiparae aged 26 and above (case) and that of 404 primiparae aged between 20 and 25 years (control) were reviewed and some data compared. Cesarean sections, instrumental deliveries, low Apgar scores at 5th minute and early neonatal death rates were significantly higher in primiparae aged 27 years and above. Hence, Cameroonian women should be enlightened about the risks of delaying first delivery. Furthermore, first pregnancies to be carried at term and first deliveries in women aged 27 and above shall be considered at high risk and consequently well followed.

• #maternal and perinatal health interventions
• #global maternal and child health
• #maternal and fetal healthcare
• #medicine