Hydrochemical characteristics of groundwater in sedimentary, metamorphic and volcanic aquifers in Ndian Division, South West Region, Cameroon.

Wells and springs are the dominant potable water sources in the area of study used by the population. Studies of the characteristics of aquifer types and the hydrochemistry of groundwater in sedimentary, metamorphic, and volcanic aquifers in the southern part of Ndian Division indicated the presence of the following three types of aquifers-sedimentary (alluvial), metamorphic (weathered/fractured gneisses) and volcanic (jointed basalts and pyroclastic materials). Fieldwork involved collecting details on rock characteristics such as the mineralogy, grain-size and texture. Physical parameters (pH, EC and temperature) were measured in-situ. Cations were determined by AAS and anions by ion chromatography. The pH values for sedimentary aquifers (5.50-8.00), metamorphic (6.10-7.40) and volcanic (5.80-7.60), reflected slightly acidic, neutral and basic water sources. The mean concentration of total dissolved solids (TDS) in the groundwater increased from metamorphic (8.84 mg/l), to volcanic (17.08 mg/l), and to sedimentary (40.48 mg/l) aquifers, representing the degree of mineralisation in these rock types. Alkalinity increased from metamorphic (14.53 mg/l), volcanic (19.18 mg/l), to sedimentary (57.64 mg/l). Based on the electrical conductivity, all the water sources were suitable  for drinking and for irrigation. Relating the major groundwater chemical facies to their geologic occurrence showed that the water in sedimentary rocks was characterised by Na-HCO3 (90%) and Ca-(HCO3)2 (10%), in the metamorphics by Na-HCO3 (100%) and in the volcanic aquifers by Ca/Mg-(HCO3)2 (70%) and Na-HCO3 (30%) water types. Based on WHO (2004) norms for potable water, 37 water sources were suitable for drinking and one water source (open well at Bekora) unsuitable due to excess nitrate and bromide concentrations of 77.28 mg/l and 0.08 mg/l respectively. Relatively based on EC and TDS, the most mineralised water was found in the sediments, the volcanics intermediate and the least mineralised water was in the metamorphic formations. The results constitute useful baseline information for future provision and management plans of water resources in the area.Keywords: Ndian Division, rock types, hydrochemistry, physical properties, groundwater, unconfinedaquifers

A hydrochemical approach to estimate mountain front recharge in an aquifer system in Tamilnadu, India

© 2017 Science Press, Institute of Geochemistry, CAS and Springer-Verlag GmbH Germany Mountain-front recharge (MFR) is a process of recharging an aquifer by infiltration of surface flow from streams and adjacent basins in a mountain block and along a mountain front (MF). This is the first attempt in India to estimate MFR along the foothills of Courtallam using hydrogeochemistry and geostatistical tools. The estimation of MFR has been carried out by collecting groundwater samples along the foothills of Courtallam. Collected water samples were analyzed for major cations and anions using standard procedures. Hydrogeochemical facies show the existence of four water types in this region. Calcium-rich water derived from gneissic rock terrain indicates significant recharge from higher elevation. Log pCO 2 and ionic strength of the samples were also calculated to identify the geochemical process. Majority of the collected samples have sodium-rich water and weak ionic strength, which indicate foothill recharge and low residence time. Silicate and carbonate weathering have an equal interplay along the foothills with a relatively large fraction of Mg from the MF. The spatial diagrams of three factors show that the southern part of the study area is dominated by both weathering and anthropogenic processes, whereas the northern part is dominated by both leaching and weathering processes. Thus, the dominant weathering process represented by the second factor indicates the large recharge process along the foothills