Abstract
The link between rainfall and groundwater recharge in the Rio del Rey Basin, which is of socio-economic importance to Cameroon, is poorly understood. Accordingly, the stable isotopes in monthly rainfall from January to December 2012 (in Lobe and Mundemba) and 52 surface water and groundwater samples were investigated. High values of δ18O and δD were recorded in the dry period (February to March), and the least values of δ18O and δD were observed in the wet period (September). This indicates that different condensation processes primarily influenced stable isotopes in rainfall as a function of the difference in moisture sources. The relationship between δD and δ18O defined the Lobe meteoric water line as δD = 7.97 δ18O + 12.48 and Mundemba water line as δD = 7.75 δ18O + 10.79. The similarity of their slopes to the global meteoric line suggests that the isotopic composition of investigated rains was not significantly affected by evaporation during precipitation. The ranges in deuterium-excess of precipitation from 5.8 to 16.56‰ suggest the source of vapour is from the Atlantic Ocean. The groundwater isotope values (ranging from −3.81 to −2.52‰ for δ18O) plotted close to and along the GMWL, showing that its isotopic composition is of meteoric origin under rapid recharge conditions. The isotopic similarity between groundwater and June–August rains suggests a significant recharge during this period.
Highlights
The availability of freshwater is necessary for any meaningful socio-economic development
Considering the total amount of rainfall in the study area (Table 1) from January to May and November to December which is 2,143 mm (26%) of the total rainfall (8259 mm), and the June to October heavy rains which is 6116 mm (74%) of the total rainfall, and based on the d-excess and δ-values, one can suggest that 74% of rainfall comes from the Atlantic Ocean, and 26% of vapour originates from recycled inland moisture
The isotope data for the rainfall samples indicated high values of δ18O and δD isotopes recorded during the dry season (November and March) and the least value in September
Summary
The availability of freshwater is necessary for any meaningful socio-economic development. Due to the lack of pipeborne water in the study area (Ndian), 80% of the population depends on groundwater sources such as hand-dug wells and springs and faced with water shortages during the dry season. Applied Water Science (2021) 11:141 abundance varies significantly with environmental factors such as the altitude of precipitation, source of moisture, amount of rainfall, and extent of evaporation (Ingraham 1998) They are used as tracers in understanding the movement of air masses and continental moisture, evaporation of water bodies and origin of surface and groundwater (Gibson et al 2005; Kendall and Coplen 2001; Liu et al 2004; Wirmvem et al 2014). The hydrological cycle is mainly a function of the precipitation regime of an equatorial climate (Etia 1980), with an alternating long rainy season that begins from April to October and a short dry season that spans from November to March
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