Groundwater Geochemistry and Saltwater Intrusion in the Dakar Coastal Area, Senegal

Abstract

Groundwater levels and water samples were collected from 20 drinking water pumping and piezometer wells in the urban area of Dakar coastal region in the year 2019. The pH-value, electrical conductivity, as well as calcium, magnesium, sodium, potassium, chloride, sulfate, bicarbonate, and nitrate concentrations were measured to assess the hydrochemical quality of the infrabasaltic aquifer in the area. The present work carried out a hydrochemical analysis to interpret the groundwater chemistry of the aquifer. The results of this chemical analysis indicate that Na + > Mg 2+ > Ca 2+ > K + was the most dominant cation sequence in the groundwater, while Cl − > 3 HCO − > 2 4 SO − > 3 NO − was the most dominant one for anions. The chemical analysis of our samples showed, that the Cl-Ca-Mg facies was dominant in the aquifer, while Cl-Na-K and HCO 3 -Na-K facies represent 20% and 10% of the groundwater sampled, respectively. A comparison of the measured groundwater quality in relation to WHO drinking water quality standards revealed that 80% of the water samples are suitable for drinking purposes. Ca enrichment, Simpson ratio, ratio of sodium chloride, and calculating Base Exchange (BEX) indices for the samples revealed that the groundwater is mainly affected by three factors: seawater intrusion due to aquifer overexploitation on one hand, and freshening processes and nitrate pollution, on the other, mainly caused by the groundwater flow from the unconfined aquifer.

Estimation of Monthly Reference Evapotranspiration with Scarce Information Using Machine Learning in Southwestern Colombia

“…Other research reports that the Turc method has historically performed well under humid (Jensen et al, 1990;Trajkovic and Kolakovic, 2009b;Fisher & Pringle, 2013;Birara et al, 2020) and tropic conditions (Tukimat et al, 2012;Lima et al, 2019;Santos et al, 2019;Monteiro et al, 2021). One of the possible reasons is that the method was initially developed under wet conditions (southern France) (Tabari, 2010;Ahmadi and Javanbakht 2020;Diouf et al, 2016). In a semiarid region in Senegal Diouf et al (2016) concluded that the Turc method showed similar high accuracy (R2>0.80) reported in this research.…”

“…One of the possible reasons is that the method was initially developed under wet conditions (southern France) (Tabari, 2010;Ahmadi and Javanbakht 2020;Diouf et al, 2016). In a semiarid region in Senegal Diouf et al (2016) concluded that the Turc method showed similar high accuracy (R2>0.80) reported in this research. Similar findings were observed in Malaysia, where Goh et al (2021) concluded that the Turc method provides the closest results to FAO-PM56 in subhumid and humid climate conditions in the absence of data, as the R2 and the MBE reported one of the 2019) concluded that the best option when meteorological data is unavailable is the Turc method given the R results (0.90) concerning FAO-PM56.…”

Spatial and Temporal Variations of the Hydrochemical Parameters in the Gravelly Aquifer of the Lower Course of Vjosa River, Albania

“…In this study, in addition to other hydrochemical ratios, the Simpson coefficient Cl − /(HCO 3 − + CO 3 2+ ) was used, too. Five classes of groundwater are distinguished in function of this coefficient; good quality (<0.5), slightly contaminated (0.5-1.3), moderately contaminated (1.3-2.8), injuriously contaminated (2.6-6.6) and highly contaminated (6.6-15.5) [28][29][30].…”

“…The r (Na + /Cl − ) ratio combined with the other considered hydrochemical parameters, may indicate the origin of the ions in groundwater, even when the Cl − ion content is rather low. The ratio r(Na + /Cl − ) < 1 is an indicator of the seawater intrusion, while r(Na + /Cl − ) > 1 indicates an anthropogenic pollution [30][31][32]. When r(Ca 2+ /Mg 2+ ) < 1, the predominance of Mg 2+ over the Ca 2+ ion content can be attributed to the seawater's intrusion [32].…”

“…The effect of the anthropogenic activity on the groundwater quality is rather complex and difficult to be determined. Nitrate ion content that originates mainly from different anthropogenic sources, is generally used to indicate this effect [14,30,31]. Heavy metals concentration has been used as another indicator of the groundwater pollution from the human activity [14,33].…”