The inhabitants of this area depend solely on contact springs as supply source of potable water. However, provision of potable water to meet the needs of the people still remains an unsolved problem. Therefore, this paper attempts to solve this problem by using Dar Zarrouk (D-Z) Parameters; Total Transverse Unit Resistance, T (Ωm 2 ) and Total Longitudinal Unit Conductance, S (Ω −1 ) to suggest optimal locations for drilling of boreholes in the study area. To attain this purpose, 50 Schlumberger Vertical Electrical Sounding (VES) curves with maximum current electrode spacing of AB/2 = 681 m were interpreted. Thus, the aquifer parameters information estimated from the (VES) curves were used to prepare contour maps of T (Ωm 2 ), S (Ω −1 ), aquifer thickness h (m), aquifer resistivity ρ (Ωm), and Water Table Depth (WTD). For effective use of these parameters, iso-thickness and iso-resistivity maps were compared with contour map of transverse resistance. The good agreement between these parameters provided the basis for identification of prolific aquiferous zones. It was observed that the Southern part of the study area majorly underlain by the Afikpo Sandstone of Nkporo Formation (Campanian-Maastrichtian), relatively showed higher T (Ωm 2 ), h (m), and ρ (Ωm) values, which implies high yield aquiferous zones. The relatively loose structure of this sandstone unit, coarse grains, and sorting enables it to be porous and permeable. The Northern part of the region which shows low values for T (Ωm 2 ), h (m), and ρ (Ωm) suggests low productivity for the aquiferous zones. The paucity of water in this parts of the study area can be explained to be as a result of the dominant geology. The high S, values at the Uburu and Okposi * Corresponding author. R. E. O. Iduma et al. 506locations in this region suggests the presence of saline aquifer. This study would be relevant to the development of effective ground water scheme and for future hydrogeological investigations in the area.

Abortive boreholes and parched wells, ascribed to the difficulty in understanding the hydrogeology of the aquifer by water borehole drillers, pose great concern to the people of the region. Mapping the spatial variability of water table depth (WTD) (m) and aquifer thickness H (m) is a vital step in optimal utilization of groundwater resources. Thus, the aim of this paper is to investigate the spatial variability of the groundwater parameters, H (m) and WTD (m) in the study area located in Nigeria, using geostatistical method of Ordinary Kriging, based on data estimated from interpreted results of fifty (50) Schlumberger Vertical Electrical Sounding (VES) curves. To attain this aim, the spatial variability of the groundwater parameters was analyzed. The result shows that the difference in directional behavior is not significant. Thus, the WTD and H were assumed as isotropic, and experimental semivariograms of logH and log(WTD) were calculated and modeled with the GS + software. It was found that, H and (WTD) data are moderately spatially correlated over the study area, and the spatial structures follow exponential model for H and spherical model for (WTD). According to the generated maps of kriged estimates of logH and log(WTD), the southern part of the study area with higher prolific aquiferous zone, shows higher kriged H-values, relative to the northern zone. The variation in the distribution of kriged WTD-values in the study region is asymmetrical. These results compare favorably in the trend patterns of distribution of the parameter values, with contour maps of a previous study in the region that indicates the distribution of H and WTD parameters. The parameters of the semivariogram models used for the analysis of the data, give insight into the spatial pattern of the groundwater parameters, H and WTD. This knowledge has improved the ability to understand the hydrogeology of the aquifer. The generated spatial variability maps of H and WTD will assist water resource managers and policymakers in the development of guidelines in judicious management of groundwater resources for drinking purposes in the study area.

Sand excavations in river beds have compromised the safety of several bridges in recent years. Large scale sand mining from river beds is now common in the Niger Delta, due to the necessity of reclaiming land for development purposes and to meet construction needs in the region. There is currently no regulation as to where sand can be mined in river channels because of the lack of adequate understanding of the risks to coastal infrastructure involved with its abstraction. The phenomenon of bridge Abutment and bank failure induced by excessive dredging of sand river bed is considered. Two types of instability were distinguished, one relating to the equilibrium slope of the riverbed and the other riverbank instability. An empirical relationship in the form X s = 3Htan(90 − α) has been developed through analysis, supported by examples that a minimum distance of 94 m (for sand river beds) from a bridge should be observed for sand abstraction in order to guaranty the safety of bridge foundation. For clay riverbeds, slightly shorter minimum distances can be considered safe. The study further shows that the capacity of sand borrowing in river channels to generate bank instability is dependent on the composition and stratigraphy beneath the river bed.