Combined influence of weir construction and sea-level rise on freshwater resources of a coastal aquifer in northern Germany

Yang, Jie; Graf, Thomas; Ptak, Thomas

Combined influence of weir construction and sea-level rise on freshwater resources of a coastal aquifer in northern Germany | Influence combinée de la construction d’un déversoir et de l’élévation du niveau de la mer sur les ressources en eau douce d’un aquifère côtier dans le nord de l’Allemagne Influencia combinada de la construcción de presas y la elevación del nivel del mar en los recursos de agua dulce de un acuífero costero en el norte de Alemania 围堰施工和海平面上升对德国北部沿海含水层淡水资源的综合影响 Influência combinada da construção de barragens e aumento do nível do mar sobre os recursos de água doce de um aquífero costeiro no norte da Alemanha

2019

Yang, Jie | Graf, Thomas | Ptak, Thomas

A significant volume of an aquifer along the coastline in the German Bight is salinized by seawater intrusion. The mean sea-level rise (MSLR) is expected to continue in the future due to global climatic change, subsequently degrading the fresh groundwater resources. To impede further salinization in the future, a solution is proposed based on weir construction in an existing canal hydraulically connected to the aquifer. The effect is twofold: (1) the elevated groundwater level can upgrade present fresh groundwater resources by shifting the saltwater–freshwater interface position further seaward, or by inhibiting its landward movement, and (2) the inland water level can be elevated, expanding surface water ponds. A fully coupled three-dimensional numerical surface-subsurface model (a modified HydroGeoSphere code) was used to simulate the effects of variable weir construction heights under different MSLR rates, and to quantify the gain of aquifer freshwater volume and loss of usable land due to surface ponding. Construction of a higher weir increases the desalinized aquifer volume and decreases the newly salinized aquifer volume under future MSLR. A minimum height of a weir was determined under a certain MSLR rate to maintain the present freshwater resource. Both weir construction and MSLR can cause the loss of land usage. Computed loss-gain ratio curves can be utilized to determine the optimal weir height, meeting the economic requirements of coastal land management under future MSLR.

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