Variation in stable isotope ratios of monthly rainfall in the Douala and Yaounde cities, Cameroon: local meteoric lines and relationship to regional precipitation cycle

Wirmvem, Mengnjo Jude; Ohba, Takayoshi; Kamtchueng, Brice Tchakam; Taylor, Eldred Tunde; Fantong, Wilson Y.; Ako, Ako Andrew

doi:10.1007/s13201-016-0413-4

Cited by 20 publications

(11 citation statements)

References 37 publications

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“…In areas where considerable topographic relief exists, the possibility that groundwater recharge occurs at high elevation should be considered. Signatures indicative of evaporative isotope effects have been identified in some groundwaters, particularly in semiarid sites (e.g., Namibia—Vogel & Van Urk, ). Many groundwater isotope compositions plot close to meteoric water lines, implying little if any evaporation occurs prior to recharge (e.g., Oman: Clark et al, ; Cameroon: Wirmvem, Ohba, et al, ). In other areas, δ 2 H and δ 18 O values plot below LMWLs, and evaporative isotope effects have likely impacted groundwater isotope compositions (Nyende et al, ).…”

Section: Threshold Rainfall Intensities For Rechargementioning

confidence: 99%

Global Isotope Hydrogeology―Review

Jasechko

2019

Reviews of Geophysics

189

124

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Groundwater 18O/16O, 2H/1H, 13C/12C, 3H, and 14C data can help quantify molecular movements and chemical reactions governing groundwater recharge, quality, storage, flow, and discharge. Here, commonly applied approaches to isotopic data analysis are reviewed, involving groundwater recharge seasonality, recharge elevations, groundwater ages, paleoclimate conditions, and groundwater discharge. Reviewed works confirm and quantify long held tenets: (i) that recharge derives disproportionately from wet season and winter precipitation; (ii) that modern groundwaters comprise little global groundwater; (iii) that “fossil” (>12,000‐year‐old) groundwaters dominate global aquifer storage; (iv) that fossil groundwaters capture late‐Pleistocene climate conditions; (v) that surface‐borne contaminants are more common in younger groundwaters; and (vi) that groundwater discharges generate substantial streamflow. Groundwater isotope data are disproportionately common to midlatitudes and sedimentary basins equipped for irrigated agriculture, but less plentiful across high latitudes, hyperarid deserts, and equatorial rainforests. Some of these underexplored aquifer systems may be suitable targets for future field testing.

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Section: Threshold Rainfall Intensities For Rechargementioning

confidence: 99%

Global Isotope Hydrogeology―Review

Jasechko

2019

Reviews of Geophysics

189

124

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“…There is evidence of depleted values with heavy rainfall, but enriched values are associated with low rainfall (Fig. 4) (Wirmvem et al, 2017). The observed depleted δ 18 O values in the rainwater within the period (Fig.…”

Section: Figurementioning

confidence: 78%

“…From this study, the 'amount' effect yielded isotopically light rainfall; suggesting that the weather is responsible for determining where on the meteoric water line the data fall. However, the meteoric water line also shifts from a point to an outlier position below/above the GMW line, due to kinetic effects associated with evaporation (Gat, 1996;Sa'nchez et al, 2013;Rai et al, 2013;Wirmvem et al, 2017). This accounts for the slight differences in the LMW lines for Cape Town, Pretoria and Thohoyandou (Fig.…”

Section: Figurementioning

confidence: 94%

“…As shown in Table 1, the annual mean d-excess values in rainwater were above 10‰ of the ocean moisture (Dansgaard, 1964), which is the primary source of most rainfall, although transpired moisture can be an important moisture source for many terrestrial regions (Brubaker et al, 1993). High d-excess values (>10‰) suggest an additional source of moisture, such as moisture recycling, among others (Wirmvem et al, 2017).…”

Section: Figurementioning

confidence: 99%

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Determination of isotopic composition of rainwater to generate local meteoric water line in Thohoyandou, Limpopo Province, South Africa

Durowoju

Odiyo

Ekosse

2019

WSA

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Hydrogen (D) and oxygen (18O) isotopic compositions of precipitation are useful tools to delineate the nature of precipitation, groundwater recharge and climatological investigations. This study investigated the isotopic composition of 12 rainfall occurrences at Thohoyandou, with the objective of generating the local meteoric water line (LMWL) and determining the factors controlling the isotopic composition of the rain. The delta (δ) values for D and 18O of the samples were determined using a Thermo Delta V mass spectrometer connected to a Gasbench. Thohoyandou rainwater showed a wide range of stable isotope values; δD values of the rainwater varied from −76.3‰ to +22.7‰ (SMOW) with a weighted mean of −9.8‰ and δ18O values ranged from −10.78‰ to +3.07‰ (SMOW) with a weighted mean of −2.7‰. δ-values of rainwater were more enriched during winter and more depleted during summer, due to the amount of rainfall and seasonal effect. The LMWL in Thohoyandou is defined by δD = 7.56δ18O + 10.64, which shows a similar slope to the global meteoric water line (GMWL) but with a slightly higher intercept, of 10.64‰ instead of 10‰. This implies that the process of rain formation in Thohoyandou occurred under equilibrium conditions which are not significantly affected by evaporation. The slightly higher d-intercept value above the GMWL reflects an additional supply of recycled moisture across the regions. This implies that there is no continental effect but inland moisture from various water bodies and vegetation.

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“…The application of some of these methods in the Yaounde area indicates that the recharge of shallow aquifer of Yaounde migmatitic basement is recent and is done directly by infiltration of precipitation without any notable change due to evaporation [61]. The average isotope contents of 18 O of rain and shallow groundwater are, respectively, −2.47 and −2.57‰ Vs-SMOW [61] with annual and monthly isotope signature differences in precipitation values [62]. Groundwater recharge appears to occur in May, October, and November (Figures 5 and 6) and increase from 30 mm/yr in the lowland to 40 mm/yr in the highland [60].…”

Section: Estimation Of Aquifer Rechargementioning

confidence: 99%

Hydrogeological Characteristics of Shallow Hard Rock Aquifers in Yaounde (Cameroon, Central Africa)

Ngoupayou¹,

Bon²,

Mboudou³

et al. 2020

Groundwater Hydrology

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The groundwater contained in the alterites is one of the main sources of water supply for many households in the city of Yaounde and its surroundings. Information from the field and laboratory studies was compiled and analyzed in order to understand the hydrogeological context of this superficial aquifer. Preliminary results show a staged morphology of the alteration mantle (regolith) of Yaounde migmatitic representative of the polyphase character of alteration processes observed in all granito-gneissic formations of the world. This mantle has a multilayer system whose soil sets could have a different hydrodynamic functioning. The values of the hydraulic conductivity have a normal distribution and vary over four orders of magnitude, attesting the variability of the hydraulic conductivity of the soft materials. The hydrometric and piezometric characteristics indicate that the aquifer has highly heterogeneous zones that would be related to the morphostructural character of the region. The δ 18 O mean values of the rain (−2.47‰) and shallow groundwater (−2.57‰) are not significantly different. They indicate that the recharge of the shallow aquifer of Yaounde Precambrian basement is recent and is done directly by infiltration of precipitation without any notable change due to evaporation. These programs relate to (a) "physical, hydrodynamic, and bacteriological characterizations of groundwater resources in the sedimentary and basement areas of Cameroon" and (b) "the impact of climate change and human activities on the water resources of Cameroon. " The activities carried out within the framework of these programs are more implemented in the alterites of the geological formations of the South Cameroon Plateau specifically those of the region of Yaounde and its surroundings [7][8][9][10][11][12]. In fact, because of the deficit service of the water distribution network, the groundwater of shallow unconfined aquifer constitutes, for many households in this region, one of the main sources of water supply.This chapter is a review of the main results obtained during the research carried out in the aquifers of the Pan-African basement of the Yaounde series in Central Africa. It is a synthesis of the results of the Theses [4,[13][14][15][16][17], DEA, DESS, and Master [11, 18, 19] studies focusing on the hydrogeological context of the upper part of the weathered and cracked basement of the Mfoundi watershed, which includes 11 sub-basins, Anga'a and Mingosso in Mefou (Figure 1). This compilation makes it possible to fill the gaps and/or to improve the knowledge of the aquifers of the weathered mantle in humid tropical zone, particularly in this part of South Cameroon facing the problems of drinking water supply.Groundwater Hydrology 12

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Variation in stable isotope ratios of monthly rainfall in the Douala and Yaounde cities, Cameroon: local meteoric lines and relationship to regional precipitation cycle

Cited by 20 publications

References 37 publications

Global Isotope Hydrogeology―Review

Global Isotope Hydrogeology―Review

Determination of isotopic composition of rainwater to generate local meteoric water line in Thohoyandou, Limpopo Province, South Africa

Hydrogeological Characteristics of Shallow Hard Rock Aquifers in Yaounde (Cameroon, Central Africa)

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