![]() High-resolution analyses of the Middle- and Late-Holocene parts of the record show moist conditions and increased Easterly/locally-derived summer precipitation contributions from 7230 ⁺¹⁶⁰/−210 to 4890 ⁺²⁸⁰/−180 cal BP and after 2840 ⁺³⁵⁰/−330 cal BP. ![]() Besides changes in the amount and proportional contribution of precipitation contributions from Westerlies during glacial and Easterlies during interglacial periods, relative sea-level change affected the continentality of Vankervelsvlei, with a distinct impact on the sites hydrological balance. ![]() Moist conditions occurred from MIS 5e to 5a and during parts of MIS 3, while drier conditions prevailed between MIS 5a and early MIS 3 and at the transition from MIS 3 to MIS 2. Our data suggest the driest conditions of the past ∼250 ka likely occurred from MIS 6 to MIS 5e, which still caused sediment deposition at Vankervelsvlei, and MIS 2, during which time there was an absence of sedimentation. This includes, for the first time in this region, analysis of both compound-specific δ²H and δ¹⁸O from leaf wax-derived n-alkanes and hemicellulose-derived sugars, respectively, to investigate hydrological changes during the Late Quaternary. A 15 m long sediment record was retrieved from this site and analysed using a multi-proxy approach. This study presents a paleoenvironmental record from Vankervelsvlei, a wetland located on the southern Cape coast in the year-round rainfall zone of South Africa. To some extent, this is due to a scarcity of natural archives, and on the other hand the available indirect hydrological proxies are not suited to distinguishing between precipitation originating from temperate Westerlies and tropical Easterlies. The Late Quaternary climate history of South Africa and, in particular, potential changes in atmospheric circulation have been subject to considerable debate. Future residence time studies should consider using a lumped parameter model (LPM) to calculate the age distribution of groundwater in these aquifers as this would provide additional insight into the sustainability of the groundwater systems. Given the interconnected nature of the aquifer systems, reduced recharge rates into the TMG aquifer will decrease groundwater flow to both the alluvial and MG aquifer and this will impact the long-term sustainability of the RAMSAR listed Verlorenvlei estuarine lake and wetlands at the catchment outlet. The discrepancy between the calculated radiocarbon and ³H/³He ages in the TMG and alluvial aquifers has been evaluated using a lumped parameter model that confirms that the TMG is strongly dominated by young groundwaters Young ³H/³He residence times calculated for groundwater in the TMG (34-57 years) and alluvial aquifers (34-47 years) implies that these systems are most susceptible to reduced groundwater recharge. Groundwater mixing has been identified within the catchment and this plays an important role in the variation in groundwater chemistry and residence time between the aquifer systems. Hydrochemistry and residence times of groundwater in the Verlorenvlei catchment have successfully been used to distinguish between the primary-porosity alluvial aquifer, the secondary-porosity Malmesbury shale aquifer (MG) and the fractured rock aquifers associated with the Table Mountain Group (TMG). Residence times were estimated using tritium and radiocarbon, and in the case of the latter, the Pearson Model has been used to correct for possible carbonate dissolution. Groundwater was sampled for δ¹⁸O, δ ²H, δ ¹☼, ¹⁴C, ³H and ³H/³He ratios in addition to cation and anion concentrations from seventeen production boreholes and two springs in the catchment. ![]() This increased reliance puts the natural environment and human dependence on groundwater into direct conflict. The groundwater systems have been put under additional stress given the recent 2015-2017 El Ninõ system that led to drought conditions along the west coast of South Africa. The Verlorenvlei catchment on the west coast of South Africa is a semi-arid region that is growing progressively more reliant on groundwater due to increased variability in precipitation and increasing agricultural productivity.
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