Groundwater exploitation in Awka (Anambra – Nigeria) and environs: Prospects, and challenges while drilling and its mitigation measures

Groundwater exploitation (borehole drilling) was carried out around Awka and environs in Anambra State, Southeastern Nigeria, to understand the underlying rock units encountered while drilling, differentiate boreholes with confined aquifers from those with unconfined aquifers, delineate the probable aquiferous zones from the borehole data, evaluate the challenges encountered while drilling (both geologic and technical), and identify mitigation measures employed to address these challenges. Detailed geologic log information of the boreholes was produced to illustrate the rock units encountered while drilling. Four rock units were identified, namely: shale, sandstone, clay, and gravel. These rock units were exposed within the Imo Formation and the Nanka Formation that underlie the study area. Results from the geologic log information of the boreholes indicate that the water table within the study area ranges from 11.2 m to 56.5 m from the soil surface, and the probable aquiferous zones vary from 6.8 m to 23.3 m in thickness. A detailed look at the lithologic logs of the boreholes show that 50% of the drilled boreholes possess confined aquifers while the remaining 50% have unconfined aquifers. A careful appraisal of the challenges encountered, which are mainly geologic, is strictly attributed to the geologic formation of the study area. Other technical challenges have been derived from mechanical faults developed during drilling.

Preliminary Conceptual Model of Hydrogeological System in The Raimanuk and its Surrounding Area on the Timor Island

There are several areas with groundwater potential in Timor island, one of which is the Raimanuk and its surrounding area. This study aims to determine the hydrogeological system in the Raimanuk and its surrounding area. The hydrogeological system is determined by the geological conditions, geomorphology, lithology, and groundwater flow patterns. Geological conditions and groundwater flow patterns are provided by conducting a field investigation. Twenty shallow wells and four springs were measured to provide the groundwater contour. The geoelectrical survey was conducted at eleven points to analyze subsurface lithology. The results show that the geology of the study area is dominated by alluvium (west area), carbonate siltstone, and crystalline limestone (middle to the east area). There are two types of aquifers in the study area: unconfined aquifers and confined aquifers with gravel sandstone lithology. The groundwater flow pattern shows that the groundwater movement is from the east to the southwest. Moreover, the groundwater also moved from the northern, southern, and western of the study area. It is implied that the aquifer’s shape at the Raimanuk area is formed as a bowl-like shape influenced by the geological, geomorphological conditions.

The 3H/3He Groundwater Age-Dating Method And Applications

Groundwater age-dating is an important tool for quantifying and managing water resources. Groundwater age is the elapsed time between recharge (at the land surface or water table) and the time when groundwater is sampled. If groundwater is sampled at the point of discharge from an aquifer, then the age represents the groundwater transit time. Groundwater that has recharged in recent decades is considered young groundwater. In many areas, the quality and quantity of young groundwater has been impacted by human activities and groundwater age-dating is useful for quantifying current and historical water and contaminant fluxes into and through aquifers. This review is focused on the tritium-helium (3H/3He) method, which is a robust and widely applied age-dating technique for young groundwater. We present the development of the 3H/3He method and practical considerations for sampling groundwater in shallow unconfined aquifers. Along the way, we highlight available resources: (1) educational software for building intuition around groundwater age-dating and selection of sampling sites and (2) software that can be used to calculate 3H/3He age from noble gas and 3H data. We also highlight strengths and potential uncertainties associated with the method. For example, while other age-dating techniques require a known historical record of tracer concentration in the atmosphere, the 3H/3He age-dating technique does not require such historical records. However, the 3H/3He method requires measurement of two tracers to produce a groundwater age estimate (“apparent age” or “tracer age”). Precise measurement of 3H and noble gases, plus careful analysis of noble gas data to calculate the tritiogenic 3He (i.e., the portion of 3He derived from decay of 3H in the aquifer) is required to calculate the groundwater apparent age. Sampling for noble gases is sometimes challenging and requires specialized sample containers and technique. We also introduce basic sampling methods in this review but highlight how practitioners should work closely with a noble gas laboratory to obtain the correct containers and assess field conditions and/or the overall feasibility of projects. Lastly, the review highlights recent applications of the 3H/3He method, including recharge rate estimation, characterization of contaminant input histories for aquifers, quantifying groundwater transit times by sampling at aquifer discharge points, and the use of isotope data to constrain and inform numerical and statistical models of groundwater and contaminant movement in the subsurface.

Sustainable Management of Springs for Water Security in Parts of the Sikkim Himalaya Region – An Overview

Springs plays a significant role in the water security of hilly people living in the Sikkim Himalayan region. Springs in the hilly regions of Sikkim contributes a maximum in the water safety, especially in the rural households. A detailed understanding about spring geology and management issues are of pre-requisite in the perspective of Sikkim for their maintenance, monitoring and management. The principal task is retaining the original unpolluted conditions of the springs and their sustainability. Geologically, the varieties of gravity springs are predominant along with Depression Spring and Fracture Spring. Structurally vulnerable plains, especially joints, fractures, and small-scale faults are true avenues for the flow path of spring water. Springs in Himalaya regions are originating from the unconfined aquifers. The yield potential of the springs are adversely affected by the factors like climatic aberration resulting in the form of variations in the rainfall intensities and tectonic activities. Chemical quality of spring water is very much within the acceptable limit of the prescribed standard, whilst away from the main city area. Springshed development and management through rainwater conservation is of essential to provide sustainable water security to the population in Sikkim.

Integral transforms for three-dimensional pumping in confined, leaky, and unconfined aquifers

Analytical or hybrid numerical-analytical solutions based on the Generalized Integral Transform Technique (GITT) are obtained for the transient three-dimensional pumping problem of aquifers with a fully penetrating vertical well between two parallel streams. The problem formulation for confined and leaky aquifers allows for achieving exact analytical solutions through integral transforms, while the unconfined aquifer case introduces a fourth kind boundary condition which leads to a coupled transformed head ordinary differential system, that can be solved either analytically or numerically. A convergence analysis is performed to illustrate the consistency of the numerical results achieved for the head distribution, as well as for the related pumping rates. Results are obtained for selected cases and comparisons with literature results are performed. A solution verification confirms the agreement of the integral transform solutions with available simulations and provides additional confidence for the analysis of a few physical parameters that influence the hydrological behavior.