@article{BauerBoersigPhametal.2022, author = {Bauer, Jonas and B{\"o}rsig, Nicolas and Pham, Van Cam and Hoan, Tran Viet and Nguyen, Ha Thi and Norra, Stefan}, title = {Geochemistry and evolution of groundwater resources in the context of salinization and freshening in the southernmost Mekong Delta, Vietnam}, series = {Journal of Hydrology: Regional Studies}, volume = {40}, journal = {Journal of Hydrology: Regional Studies}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2214-5818}, doi = {10.1016/j.ejrh.2022.101010}, pages = {17}, year = {2022}, abstract = {Study region: Ca Mau Province (CMP), Mekong Delta (MD), Vietnam. Study focus: Groundwater from deep aquifers is the most reliable source of freshwater in the MD but extensive overexploitation in the last decades led to the drop of hydraulic heads and negative environmental impacts. Therefore, a comprehensive groundwater investigation was conducted to evaluate its composition in the context of Quaternary marine transgression and regression cycles, geochemical processes as well as groundwater extraction. New hydrological insights for the region: The abundance of groundwater of Na-HCO3 type and distinct ion ratios, such as Na+/Cl-, indicate extensive freshwater intrusion in an initially saline hydrogeological system, with decreasing intensity from upper Pleistocene to deeper Miocene aquifers, most likely during the last marine regression phase 60-12 ka BP. Deviations from the conservative mixing line between the two endmembers seawater and freshwater are attributed to ion-exchange processes on mineral surfaces, making ion ratios in combination with a customized water type analysis a useful tool to distinguish between salinization and freshening processes. Elevated salinity in some areas is attributed to HCO3- generation by organic matter decomposition in marine sediments rather than to seawater intrusion. Nevertheless, a few randomly distributed locations show strong evidence of recent salinization in an early stage, which may be caused by the downwards migration of saline Holocene groundwater through natural and anthropogenic pathways into deep aquifers.}, language = {en} } @article{KuehnAltmannsbergerHens2016, author = {K{\"u}hn, Michael and Altmannsberger, Charlotte and Hens, Carmen}, title = {Waiweras WarmwasserreservoirWelche Aussagekraft haben Modelle?}, series = {Grundwasser : Zeitschrift der Fachsektion Hydrogeologie in der Deutschen Gesellschaft f{\~A}¼r Geowissenschaften (FH-DGG)}, volume = {21}, journal = {Grundwasser : Zeitschrift der Fachsektion Hydrogeologie in der Deutschen Gesellschaft f{\~A}¼r Geowissenschaften (FH-DGG)}, publisher = {Springer}, address = {Heidelberg}, issn = {1430-483X}, doi = {10.1007/s00767-016-0323-2}, pages = {107 -- 117}, year = {2016}, abstract = {The warm water geothermal reservoir below the village of Waiwera in New Zealand has been known by the native Maori for centuries. Development by the European immigrants began in 1863. Until the year 1969, the warm water flowing from all drilled wells was artesian. Due to overproduction, water up to 50 A degrees C now needs to be pumped to surface. Further, between 1975 and 1976, all warm water seeps on the beach of Waiwera ran dry. Within the context of sustainable water management, hydrogeological models must be developed as part of a management plan. Approaches of varying complexity have been set-up and applied since the 1980s. However, none of the models directly provide all results required for optimal water management. Answers are given simply to parts of the questions, nonetheless improving resource management of the geothermal reservoir.}, language = {de} }