TY - JOUR A1 - Bauer, Jonas A1 - Börsig, Nicolas A1 - Pham, Van Cam A1 - Hoan, Tran Viet A1 - Nguyen, Ha Thi A1 - Norra, Stefan T1 - Geochemistry and evolution of groundwater resources in the context of salinization and freshening in the southernmost Mekong Delta, Vietnam JF - Journal of Hydrology: Regional Studies N2 - 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. KW - Ca Mau KW - Hydrogeology KW - Delta aquifer system KW - Salinity KW - Freshwater KW - Seawater intrusion Y1 - 2022 U6 - https://doi.org/10.1016/j.ejrh.2022.101010 SN - 2214-5818 VL - 40 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wilhelms, Andre A1 - Börsig, Nicolas A1 - Yang, Jingwei A1 - Holbach, Andreas A1 - Norra, Stefan T1 - Insights into phytoplankton dynamics and water quality monitoring with the BIOFISH at the Elbe River, Germany JF - Water N2 - Understanding the key factors influencing the water quality of large river systems forms an important basis for the assessment and protection of cross-regional ecosystems and the implementation of adapted water management concepts. However, identifying these factors requires in-depth comprehension of the unique environmental systems, which can only be achieved by detailed water quality monitoring. Within the scope of the joint science and sports event "Elbschwimmstaffel" (swimming relay on the river Elbe) in June/July 2017 organized by the German Ministry of Education and Research, water quality data were acquired along a 550 km long stretch of the Elbe River in Germany. During the survey, eight physiochemical water quality parameters were recorded in high spatial and temporal resolution with the BIOFISH multisensor system. Multivariate statistical methods were applied to identify and delineate processes influencing the water quality. The BIOFISH dataset revealed that phytoplankton activity has a major impact on the water quality of the Elbe River in the summer months. The results suggest that phytoplankton biomass constitutes a substantial proportion of the suspended particles and that photosynthetic activity of phytoplankton is closely related to significant temporal changes in pH and oxygen saturation. An evaluation of the BIOFISH data based on the combination of statistical analysis with weather and discharge data shows that the hydrological and meteorological history of the sampled water body was the main driver of phytoplankton dynamics. This study demonstrates the capacity of longitudinal river surveys with the BIOFISH or similar systems for water quality assessment, the identification of pollution sources and their utilization for online in situ monitoring of rivers. KW - water quality KW - phytoplankton KW - river dynamics KW - multisensor system KW - online KW - monitoring KW - high spatial resolution KW - multivariate statistics Y1 - 2022 U6 - https://doi.org/10.3390/w14132078 SN - 2073-4441 VL - 14 IS - 13 PB - MDPI CY - Basel ER - TY - JOUR A1 - Böhnke, Denise A1 - Krehl, Alice A1 - Moermann, Kai A1 - Volk, Rebekka A1 - Lützkendorf, Thomas A1 - Naber, Elias A1 - Becker, Ronja A1 - Norra, Stefan T1 - Mapping urban green and its ecosystem services at microscale-a methodological approach for climate adaptation and biodiversity JF - Sustainability / Multidisciplinary Digital Publishing Institute (MDPI) N2 - The current awareness of the high importance of urban green leads to a stronger need for tools to comprehensively represent urban green and its benefits. A common scientific approach is the development of urban ecosystem services (UES) based on remote sensing methods at the city or district level. Urban planning, however, requires fine-grained data that match local management practices. Hence, this study linked local biotope and tree mapping methods to the concept of ecosystem services. The methodology was tested in an inner-city district in SW Germany, comparing publicly accessible areas and non-accessible courtyards. The results provide area-specific [m(2)] information on the green inventory at the microscale, whereas derived stock and UES indicators form the basis for comparative analyses regarding climate adaptation and biodiversity. In the case study, there are ten times more micro-scale green spaces in private courtyards than in the public space, as well as twice as many trees. The approach transfers a scientific concept into municipal planning practice, enables the quantitative assessment of urban green at the microscale and illustrates the importance for green stock data in private areas to enhance decision support in urban development. Different aspects concerning data collection and data availability are critically discussed. KW - climate adaptation KW - urban green KW - mapping KW - ecosystem service cascade KW - model KW - surface type-function-concept KW - planning indicators KW - city district KW - level KW - urban planning practice KW - climate change Y1 - 2022 U6 - https://doi.org/10.3390/su14159029 SN - 2071-1050 VL - 14 IS - 15 PB - MDPI CY - Basel ER - TY - JOUR A1 - Hoan, Tran Viet A1 - Richter, Karl-Gerd A1 - Borsig, Nicolas A1 - Bauer, Jonas A1 - Ha, Nguyen Thi A1 - Norra, Stefan T1 - An improved groundwater model framework for aquifer structures of the quaternary-formed sediment body in the southernmost parts of the Mekong Delta, Vietnam JF - Hydrology : open access journal N2 - The Ca Mau peninsula (CMP) is a key economic region in southern Vietnam. In recent decades, the high demand for water has increased the exploitation of groundwater, thus lowering the groundwater level and leading to risks of degradation, depletion, and land subsidence, as well as salinity intrusion in the groundwater of the whole Mekong Delta region. By using a finite element groundwater model with boundary expansion to the sea, we updated the latest data on hydrogeological profiles, groundwater levels, and exploitation. The basic model setup covers seven aquifers and seven aquitards. It is determined that the inflow along the coastline to the mainland is 39% of the total inflow. The exploitation of the study area in 2019 was 567,364 m(3)/day. The most exploited aquifers are the upper-middle Pleistocene (qp(2-3)) and the middle Pliocene (n(2)(2)), accounting for 63.7% and 24.6%, respectively; the least exploited aquifers are the upper Pleistocene and the upper Miocene, accounting for 0.35% and 0.02%, respectively. In the deeper aquifers, qp(2-3) and n(2)(2), the change in storage is negative due to the high exploitation rate, leading to a decline in the reserves of these aquifers. These groundwater model results are the calculations of groundwater reserves from the coast to the mainland in the entire system of aquifers in the CMP. This makes groundwater decision managers, stakeholders, and others more efficient in sustainable water resources planning in the CMP and Mekong Delta (MKD). KW - groundwater modeling KW - hydrogeology KW - aquifers system KW - water balance; KW - validation of model KW - Ca Mau peninsula KW - Kien Giang KW - Soc Trang KW - Hau Giang KW - Bac Lieu Y1 - 2022 U6 - https://doi.org/10.3390/hydrology9040061 SN - 2306-5338 VL - 9 IS - 4 PB - MDPI CY - Basel ER -