Assessment of the Nubian aquifer characteristics by combining geoelectrical and pumping test methods in the Omdurman area, Sudan

Abstract

The recent research is carried out to model the characteristics and productivity of the groundwater aquifer in the Omdurman area, Sudan, by combining electrical resistivity and pumping test methods. Omdurman is the most populous city known as the traditional capital of Sudan. Vertical electrical sounding (VES) survey using Schlumberger array is carried out along four profiles to delineate the potential groundwater zones. Application of 1D geophysical inversion revealed five geoelectric layers, including recent deposits, clay, silicified and ferruginous sandstone, and sandstone. Additionally, based on the outcome of VES inversion, Dar Zarrouk parameters, including transverse resistance and longitudinal conductance, were calculated to model the aquifer characteristics. The transverse resistance ranged from 5587 to 309,853 Ωm2, while the longitudinal conductance varied between 0.14 and 2.5 Ω−1. The hydraulic conductivity and transmissivity are further measured using the VES data, ranging from 1.4 to 5.2 m/d and 435 to 1564 m2/day, respectively. The step-drawdown pumping tests were performed to evaluate the aquifer characteristics and thus validate the result of the geoelectrical method. The transmissivity obtained from the step test varied between 583 and 1226 m2/day, showing an acceptable agreement with those of geoelectrical data. Based on the measured parameters, the aquifer is classified as highly productive and ideal for groundwater development. The step drawdown test was further used to assess the performance of groundwater wells. The results indicated that faulty well design and inappropriate pumping rates influence some wells in the study area, resulting in high drawdown and low well efficiency. Overall, the objectives of the study were successfully achieved; nonetheless, detailed hydrogeological and geophysical investigations are recommended for comprehensive evaluation of the groundwater aquifer.

Application of GIS-based machine learning algorithms for prediction of irrigational groundwater quality indices

“…This aquifer is classified as highly productive, with an average transmissivity of 700 m 2 /day (Elkrail and Adlan, 2019;Mohammed M. et al, 2023). Given that there is relatively minimal recharge from rainfall, the Nile River and ephemeral streams are the primary sources of groundwater recharge to the Nubian formation (Mohammed et al, 2023c). As a result, groundwater levels range from 366.6 m in the western parts near Nile River to 294 m in the eastern part (Figure 3).…”

Assessing heterogeneous groundwater systems: Geostatistical interpretation of well logging data for estimating essential hydrogeological parameters

“…One critical parameter in hydrogeology, hydraulic conductivity, presents particular difficulties due to its nonlinearity to other petrophysical and fluid properties, making its accurate prediction from geophysical data problematic 22 , 23 . Consequently, groundwater researchers often resort to pumping experiments 24 , which are costly and time-consuming to quantify hydraulic conductivity 25 . In this context, Csókás 26 introduced an improved methodology for estimating hydraulic conductivity in loosely consolidated hydrogeological units, exclusively relying on well-logging data.…”

Investigation of petrophysical and hydrogeological parameters of the transboundary Nubian Aquifer system using geophysical methods

“…The Nubian Aquifer System (NAS) is a significant transboundary aquifer that serves as a crucial groundwater reservoir. It covers the dry areas of Egypt, Libya, Chad, and Sudan, making it one of the largest in the world (Sultan Araffa et al, 2009;Mohamed et al, 2017;Mohamed, 2019;Mohammed et al, 2023c). The aquifers in question are of great importance in maintaining water resources and supporting the lifestyles of people in the nations mentioned (Voss and Soliman, 2014).…”

“…It assumes that the aquifer is homogenous, isotropic, and has an infinite extent and neglects groundwater storage during the test (Misstear, 2001). Moreover, in heterogeneous aquifer systems, the estimation of these parameters is restricted to the measurement point; therefore, error is inevitable during the generalization of the results (Avci et al, 2010;Mohammed et al, 2023c;Flores et al, 2023;Yang et al, 2023). To address these drawbacks, geophysical methods are widely applied for groundwater exploration and aquifer characterization since they provide a continuous estimate of hydrogeological and petrophysical parameters (Szabó et al, 2015;Fejes et al, 2021;Mohammed et al, 2023e).…”