Geoelectric Evaluation of Aquifer Potential and Vulnerability of Northern Paiko, Niger State, Nigeria
This study was carried out using vertical electrical sounding (VES) to evaluate the groundwater potential and the aquifer protective capacity of Northern Paiko. Sixty vertical electrical soundings were obtained across the study area using Schlumberger electrode configuration. Three to four geoelectric layers were delineated from the interpreted results. The stratigraphy of the subsurface shows: topsoil (62.8–3082 Ωm), weathered layer (15.2–80 368 Ωm), fractured layer (191–236 672 Ωm), and the fresh basement (79.9–308 865 Ωm). The weathered layer was delineated as the major aquiferous horizon. From the results, the resistivity, thickness, and longitudinal conductance maps were drawn. It was observed that groundwater potential is low in about 76.7% of the study area. This study has also shown that the aquifer protective capacity of most parts of the study area is poor (83.3%), thus rendering the aquifer vulnerable to contamination.
Geophysical and physicochemical investigation of groundwater repositories in Njaba LGA of Imo State, eastern Nigeria
Geoelectric survey integrated with physicochemical method of water analysis was used to investigate the aquifer repositories in Njaba, Imo State, eastern Nigeria. This was done in 15 locations using vertical electrical sounding (VES) employing Schlumberger electrode configuration, and water samples from four boreholes were analyzed in the laboratory. The resistivity data were interpreted using forward and iterative least square inversion modeling of WINRESIST software. Four to six geoelectric layers and the VES characteristic curve types were obtained. The resistivity values vary across the study area with their respective depths and thicknesses. The aquifer resistivities range from 402.50 to 16,484.40 Ωm. The hydraulic parameters estimated include: Dar Zarrouk parameters (longitudinal conductance and transverse resistance), hydraulic conductivity and transmissivity. The longitudinal conductance ranges between 0.0004 and 0.0763 Ω−1, and transverse resistance ranges between 6823.40 and 245,320.00 Ωm2. The range of hydraulic conductivity and transmissivity varies from 0.0450 to 1.4363 m day−1 and 0.3195 to 44.0944 m2 day−1, respectively. The contour maps generated using Surfer software package displayed the variations of these parameters across the study area. The results obtained indicate that the study area has low groundwater potential based on the transmissivity values and may be prone to surface contamination due to its poorly protected aquiferous units. The concentrations of the ions in the water samples measured were compared with the World Health Organization (WHO) standard for drinking water and were found to be below WHO standard. The sodium percentage and sodium absorption ratio were calculated in order to determine the suitability of the groundwater for agriculture.
Die Populationsdynamik Von Canthocampt Us Staphylinus (Jurine) (Copepoda, Harpacticoida) Im Litoral Des Bodensees
The population dynamics of Canthocamptus staphylinus in the littoral zone of Lake Constance are described (fig. 2). Adult animals aestivate as cysts. The main part of the population emerges from the cysts in autumn. During the resting stage and the first spell after emerging, mortality is very low (fig. 3). Reproduction, expressed as numbers of ovigerous females, begins in November and reaches its maximum in January. The new generation becomes adult in May/June and encysts without previous reproduction. According to Sarvala (1979) it may be possible, that in littoral populations dormancy is induced by long day periods and temperatures of over 12° C (figs. 1, 2). In the profundal zone C. staphylinus also forms cysts, however, both light and temperature are not likely to induce this stage in depths of over 60 m.