Riverine‐Based Aquifers and Riparian Exchange: A Conceptual Discussion

This chapter presents a conceptual discussion of the aquifers that typically occur along river channels and the riparian exchange of water as influenced by valley and channel type and management. Definitions of alluvial and bedrock river channel, based on literature, are provided while highlighting their general attributes and exchange options. Conceptual aquifer models occurring along alluvial and bedrock river channels are then described and presented with respect to groundwater‐surface exchanges and solute fate and transport. There is theoretical reasoning to suggest that channel aquifers and concordant riparian zones can be conceptualized and classified based on valley type and the nature of the river channel hosting the aquifer. The information presented in the conceptual models can be used during desktop studies to strategically plan the optimal management for aquifer and riparian protection and restoration activities subject to anthropogenic risk. Riparian zone management is needed more so today, because basin land use in many parts of the world has advanced to the point of creating both water quantity and quality disequilibrium

Sustainability of Human, Plant, and Aquatic Life: A Theoretical Discussion from Recharge to Discharge

Groundwater comprises about 1.7% of the earth’s total water and over 30% of the total freshwater supply. Is there enough groundwater to meet human, plant, and aquatic life needs? In many parts of the world, yes; however, with changing demographics and concordant land use and climate change, the distribution and availability of groundwater may not be sustainable. This chapter considers some of the current and past stressors of groundwater by using case examples from around the world. We explore hydrogeologic settings where anthropogenic activity has impaired or has the potential to impair human, plant, and aquatic life. Stressors include well pumping, mining, climate change, chemical use, water law/regulation, and manipulation of surface water. These examples serve to inform those concerned about sustainable management and offer insight into the links between groundwater, climate, and land use

Groundwater Quality Assessment of Shallow Aquifer Hand Dug Wells in Rural Localities of Ilorin Northcentral Nigeria: Implications for Domestic and Irrigation Uses

Published ArticleThis research determined the quality of shallow hand dug wells for domestic and irrigation uses in the rural localities of Ilorin, Northcentral Nigeria. Twenty (20) water samples were collected from shallow hand dug wells in the study area during wet and dry seasons. The water samples were assessed for physical and chemical qualities. Results indicates that pH of water samples is acidic to alkaline which ranges between 6.7 and 7.6 in dry season and ranges from 6.6 to 7.2 for wet season. The pH values fall within the permissible limits of World Health Organization (WHO) standards and Nigerian Drinking Water Quality Standards (NDWQS). Quality standards of chemical parameters analysed in the water samples falls within the permissible limits. MgHCO3 is considered as the most dominant water type in both seasons. Magnesium occurrence was traced to the disintegration of rock minerals while dominance of bicarbonates in the water contributed mostly by carbon dioxide charged recharge water during precipitation. Irrigation parameters tested includes Soluble Sodium Percentage (SSP), Residual Sodium Bicarbonate (RSBC), Sodium Absorption Ratio (SAR) and Magnesium Adsorption Ratio (MAR) which all indicates that the water samples are also suitable for irrigation

A New Method For Estimating Hydraulic Conductivity In Un-Screened Concrete-Lined Large-Diameter Hand-Dug Wells

ArticleThe use of large-diameter hand-dug wells as main source of rural water supply for drinking, domestic and irrigation uses in many developing countries has offer an opportunity to developed Darcy-based methods for estimating hydraulic conductivity in screened-lined large-diameter hand-dug wells to determine the yield and discharge potential of the wells. However, in many rural areas of sub-Saharan African countries, the use of unscreened concrete lining is most common method of protecting large-diameter hand-dug wells against collapsing and pollution due to the affordability of the method. The use of un-screened concrete lining prevents horizontal water flow to the well and inflow of water in un-screened concrete well occur through well base, therefore, existing Darcy-based method not suitable to estimate hydraulic conductivity for this well design. This study proposed a new method for estimating aquifer hydraulic conductivity for un-screened concrete-lined largediameter hand-dug wells. To demonstrate the viability of the new method, field recovery tests were conducted in twelve (12) un-screened concrete lined large-diameter hand-dug wells to estimate apparent hydraulic conductivity (Ka) of aquifer formation. The twelve (12) un-screened concrete wells were screened for the second round of recovery tests to estimate horizontal hydraulic conductivity K. The results showed that the estimated apparent hydraulic conductivity Ka values were lower than the horizontal hydraulic conductivity K values and this show effect of un-screened concrete-lining. A relationship between Ka and K was established to make a correction factor for estimation of K from Ka by a regression analysis which showed a linear regression of 0.78 with a significant strong relationship of 0.00 between Ka and K using a bivariate Pearson correlation coefficient. The new method will be useful to determine well yield most especially in the rural areas of developing countries where un-screened concrete-lined large-diameter hand-dug wells are being practiced

Groundwater - Resource Characterisation and Management Aspects

This book covers aspects of groundwater resource characterisation and management. The inherent heterogeneous and isotropic nature of aquifers coupled with the unpredictable effects of climate change calls for continuous improvement and understanding of hydrogeology site characterisation techniques in theory and application to better understand and manage groundwater. We believe that this book will be useful for various professionals involved in groundwater-related work to improve the theoretical and practical understanding of hydrogeology site characterisation techniques and groundwater resource management skills

Intrinsic vulnerability assessment of shallow aquifers of the sedimentary basin of southwestern Nigeria

The shallow groundwater of the multi-layered sedimentary basin aquifer of southwestern Nigeria was assessed based on its intrinsic vulnerability property. The vulnerability evaluation involves determining the protective cover and infiltration condition of the unsaturated zone in the basin. This was achieved using the PI (P stands for protective cover effectiveness of the overlying lithology and I indicates the degree of infiltration bypass) vulnerability method of the European vulnerability approach. The PI method specifically measures the protection cover and the degree to which the protective cover is bypassed. Intrinsic parameters assessed were the subsoil, lithology, topsoil, recharge and fracturing for the protective cover. The saturated hydraulic conductivity of topsoil, infiltration processes and the lateral surface and subsurface flow were evaluated for the infiltration bypassed. The results show moderate to very low vulnerability areas. Low vulnerability areas were characterised by lithology with massive sandstone and limestone, subsoils of sandy loam texture, high slopes and high depth to water table. The moderate vulnerability areas were characterised by high rainfall and high recharge, low water table, unconsolidated sandstones and alluvium lithology. The intrinsic vulnerability properties shown in vulnerability maps will be a useful tool in planning and monitoring land use activities that can be of impact in groundwater pollution

Geoelectrical Characterization of Coastal Aquifers in Agbado-Ijaye, Lagos, Southwestern Nigeria; Implications for Groundwater Resources Sustainability

Water is a natural resource; its availability depends on climatic and geological conditions, and it is invariably controlled by human activities. Agbado-Ijaye lies within a coastal area, where local communities have been facing incessant water shortages, especially during the dry season. This study investigated the groundwater-bearing geological unit(s) using hydrogeophysical techniques in the coastal environment. The electrical resistivity technique, involving vertical electrical sounding (VES) and two-dimensional (2D) electrical resistivity imaging via Wenner array electrode configuration, was used to characterize the geoelectric distribution. Twenty VES stations were investigated and current electrodes (AB/2 m) spacing expanded from 1–200 m; four 2D electrical resistivity imaging traverses having a length of 200 m each and interelectrode spacing of 10 m (level 1) to 60 m (level 6) was adopted. Four geoelectric units were delineated, namely: topsoil (15–251 Ωm), clayey (28–100 Ωm), clayey sand (125–190 Ωm) and sandy (205–876 Ωm) with thicknesses ranging from 0.7–1.3 m, 4.1–19.0 m, 2.6–15.6 m and undefined depth, respectively. The 2D imaging sections also detected similar geoelectric layers, corroborating the VES-derived sections. The inverted sections delineated two different aquifers: the shallower low-yield aquifer comprising sandy clay/clayey sand units with a maximum depth of about 5.5 m. This layer is adjudged to be the continental plain sand of the Benin Formation. The deeper high-yield aquifer with a maximum depth of 30.4 m is a beach sand unit that belongs to the Tertiary Alluvium of the Dahomey Basin. The study showed that hydrogeophysical investigation is vital in exploring, developing, and managing coastal groundwater resources