| During the development of the Mekong Delta, a complex sequence of confined aquifers and aquitards were formed, which differ in their regional appearance and extent. In Ca Mau Province, which is located in the most southern part of the Mekong Delta in Vietnam, groundwater is the major source of freshwater. Heavy groundwater overexploitation of three main aquifers between 90 m and 250 m have induced a drop of hydraulic heads as well as compaction of those stratigraphic units, leading to severe local land subsidence up to several centimeters per year (Erban et al. 2014). Additive processes such as natural compaction of the uppermost sediments, salinization and erosion processes, a decline of fluvial sediment supply by the Mekong River due to upstream dam constructions (Allison et al. 2017) as well as sea level rise due to global climate change threaten the region severely. Overall, the problems can be summarized as a progressive “loss of land and fresh water”. In order to develop effective and sustainable counter measures, the existing system need first be understood in detail. One essential part of this process is to gain insights into the hydrogeology and groundwater geochemistry dynamics. Therefore, extensive sampling campaigns emphasizing water quality issues were conducted to characterize all types of water in Ca Mau Province, including groundwater, surface- and rainwater, storage water as well as coastal waters. Supported by detailed aquifer modeling and remote sensing techniques, obtained information will be used in a later step to develop a holistic and integrated approach for groundwater substitution by alternative fresh water resources with the aim to mitigate salinization and most importantly land subsidence processes.<br>
Introducing alternative water resources, however, will not only be challenging from a technical and environmental point of view but also from a social perspective. Suppobtorted by the local Provincial People’s Committees (PPC), questionnaires and group interviews were conducted in all districts of Ca Mau Province to identify the spatial distribution of the required water management solutions and infrastructures as well as the acceptance for alternative water resources. It is essential to inform the people about environmental challenges and threats and to raise a cause-effect related awareness for such topics. In addition, alternative water resources must be evaluated according to the demands of the local people and their willingness to change their current water related habits. In this context, water balances for various purposes must be elaborated covering water for drinking, hygiene, irrigation and aquaculture as well as further issues. To identify alternative water resources, understanding the social acceptance is the first priority step for developing new water utilization concepts. |
