Coupling End-Member Mixing Analysis and Isotope Mass Balancing (222-Rn) for Differentiation of Fresh and Recirculated Submarine Groundwater Discharge Into Knysna Estuary, South Africa

2018 ◽  
Vol 123 (2) ◽  
pp. 952-970 ◽  
Author(s):  
E. Petermann ◽  
K. Knöller ◽  
C. Rocha ◽  
J. Scholten ◽  
R. Stollberg ◽  
...  
Keyword(s):  
South Africa ◽  
Submarine Groundwater Discharge ◽  
Groundwater Discharge ◽  
Submarine Groundwater ◽  
Mass Balancing

scholarly journals Land Use Pollution Potential of Water Sources Along the Southern Coast of South Africa

2018 ◽  
Vol 4 (1) ◽  
pp. 7-20 ◽  
Author(s):  
Hanlie Malherbe ◽  
Michael Gebel ◽  
Stephan Pauleit ◽  
Carsten Lorz
Keyword(s):  
South Africa ◽  
Land Use ◽  
Coastal Water ◽  
Submarine Groundwater Discharge ◽  
Groundwater Resources ◽  
Groundwater Discharge ◽  
Nitrogen Pollution ◽  
Southern Coast ◽  
Submarine Groundwater ◽  
Groundwater Nitrogen

AbstractSince the 1990’s, the groundwater quality along the southern coast of the Western Cape Province of South Africa has been affected by increasing land use activities. Groundwater resources have become increasingly important in terms of providing good quality water. Polluted coastal groundwater as a source of submarine groundwater discharge also affects the quality of coastal water. For this study, land use activities causing groundwater pollution and areas at particular risk were identified. An assessment approach linking land use/land cover, groundwater and submarine groundwater discharge on a meso-scale was developed and the methods applied to two study regions along the southern coastal area. Dryland and irrigated crop cultivation, and urbanized areas are subject to a “high” and “very high” risk of groundwater nitrogen pollution. Application of fertilizer must be revised to ensure minimal effects on groundwater. Practice of agricultural activities at locations which are not suited to the environment’s physical conditions must be reconsidered. Informal urban development may contribute to groundwater nitrogen pollution due to poor waste water disposal. Groundwater monitoring in areas at risk of nitrogen pollution is recommended. Land use activities in the submarine groundwater discharge contribution areas was not found to have major effects on coastal water.

scholarly journals Improved Approach for the Investigation of Submarine Groundwater Discharge by Means of Radon Mapping and Radon Mass Balancing

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 749 ◽  
Author(s):  
Schubert ◽  
Petermann ◽  
Stollberg ◽  
Gebel ◽  
Scholten ◽  
...  
Keyword(s):  
Mass Balance ◽  
Submarine Groundwater Discharge ◽  
Large Scale ◽  
Groundwater Discharge ◽  
Distribution Patterns ◽  
Hydrogeological Model ◽  
Fresh Groundwater ◽  
Area Of Interest ◽  
Submarine Groundwater ◽  
Mass Balancing

The paper presents an improved approach for investigating submarine groundwater discharge (SGD) based on radon mapping and radon mass balancing in the coastal sea. While the use of radon as an environmental tracer in SGD studies is well-established, we identified based on our longstanding experience six methodical shortcomings of the conventional approach and suggest corresponding developments. The shortcomings include: (1 and 2) inadequate consideration of both detection equipment response delay and influence of tidal stage; (3 and 4) incorrect quantification of radon losses, due to offshore mixing and degassing resulting in a potentially incorrect radon mass balance; (5) inaccurate determination of the terrestrial groundwater endmember, due to inhomogeneous radon distribution in the coastal aquifer; and (6) difficulties in distinguishing between discharged fresh groundwater and recirculated seawater. The improved approach is practically demonstrated in a step by step manner in a large-scale field study, which was carried out in False Bay (South Africa) and which consisted of two parts, namely (i) qualitative SGD localization along the entire False Bay coastline based on coastal radon distribution patterns and (ii) quantitative SGD investigation within a defined coastal area of interest (AOI) based on a radon mass balance (RMB). The plausibility of the AOI related results was evaluated by a hydrogeological model, used for qualitative SGD localization, and a hydrological model, applied for estimating groundwater recharge within the AOI catchment.

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