GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 30-5
Presentation Time: 9:00 AM-5:30 PM


RAMATLAPENG, Goabaone1, COUNTS, Nicholas T.2, BIKUU, Victorine A.3, ELLA, Kahnyuy4, FREGOSO-SANCHEZ, Diana Carolina5, COMPTON, Kalyn6, GERMAINE CORINE, Ngameni Youaleu7, CHARLES, Njilah8, ALI, Hendratta2, NJILAH, Isaac Knofor7 and ATEKWANA, Eliot9, (1)Department of Geological Sciences, University of Delaware, 210 South College Ave. Newark, DE, 312 Delaware circle, Newark, DE 19716, (2)Department of Geological Sciences, Fort Hays State University, 600 Park Street, Hays, Kansas, Hays, KS 67601, (3)Department of Geological Sciences, University of Douala, Cameroon, Carrefour Ange Raphaƫl, Douala, Cameroon, Douala, Cameroon, (4)Department of Microbiology, University of Buea, Buea, Cameroon, Buea, Cameroon, (5)Department of Civil and Environmental Engineering, California State University, Fullerton, 800 N. State College Blvd, Fullerton, CA 92831; California State University of Fullerton, 800 N. State College Blvd, Los Angeles, CA 92831, (6)Department of Biological Sciences, Fort Hays State University, Hays, KS 67601; Department of Geological Sciences, Fort Hays State University, 600 Park Street, Hays, Kansas, Hays, KS 67601, (7)Department of Earth Science, University of Yaounde, Yaounde, Cameroon, (8)Department of Arts, letters and social sciences, Yaounde, (9)Department of Geological Sciences, University of Delaware, Newark, DE 19717

The city of Douala (210 km2) in the Wouri estuary is home to 3 million people who mostly depend on groundwater for domestic and industrial activities. The importance of groundwater as a resource poses a critical need for understanding how the estuary affects groundwater chemistry. The goal of this study is to assess the influence of tidal regime on groundwater quality. Our objectives are to (1) document the temporal variations in the physicochemical parameters of groundwater, (2) determine the extent of tidal influence on the interaction between groundwater and estuarine water, and (3) examine the effect of the estuarine water on groundwater quality. Measurements of physicochemical parameters were made in 3 wells located between 150-300 m from the shoreline. Physicochemical parameters were logged at minute intervals for 48 h using a levelogger. Temperature, pH, salinity, TDS, ORP and DO were recorded using a multiparameter probe. Alkalinity was determined by titration and ionic concentrations were obtained by spectrophotometry. Samples were collected for DIC, DOC, POC, cation and anion analyses. Water levels fluctuated by 0.4 m, pH ranged between 5.9 and 6.7 and conductivity varied between 780 and 820 µS/cm. The mean salinity in the groundwater was 1.26 (±0.05) and DO varied between 27 and 66%. Fe, NO3-, PO4 and NH4+ concentrations varied between 20 and 24 mg/l, 15 and 21 mg/l, 0.3 and 0.5 mg/l and 1.5 and 3.9 mg/l, respectively. Fluctuations in groundwater levels were concomitant with tidal cycles, but not with conductivity trends. Although concentrations of ions and metals in groundwater are high, they do not appear to be affected by estuarine water incursion. We infer that groundwater levels were responding to tidal energy but not to sea flow into groundwater. We suggest that the contribution of ions is from other sources such as aquifer geology and anthropogenic sources.