Influence of heterogeneity in the preservation of subsurface saline paleowater in coastal deltas
Abstract
Saline groundwater emplaced during previous marine transgressions limits freshwater resources in coastal deltas. This research uses morphodynamic and hydrogeologic modeling to simulate the formation of coastal deltas throughout the Holocene to explore how delta geomorphology impacts the permeability distribution, and ultimately, the distribution of fresh and saline water as these dynamic landscapes evolve. Delft3D, a morphodynamic model, is used to create two-dimensional sediment deposits representative of coastal deltas formed under varying morphodynamic conditions, including changes in median grain size as well as fluvial and marine forces. Spatially varying porosity and hydraulic conductivity values are calculated to translate the sediment being deposited into heterogeneous aquifer and aquitard structures. These structures are the hydrogeologic inputs to density-dependent groundwater flow and solute transport models used for simulating groundwater freshening over the past eight thousand years of modern delta formation. Spatial variability in basin-scale aquifer and aquitard heterogeneity is shown to control the preservation of saline paleowater deposits in deltaic environments. Understanding the processes controlling the preservation of coastal salinity allows for more accurate assessment of freshwater availability in these often highly populated and environmentally productive landscapes.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H53I1864A
- Keywords:
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- 1817 Extreme events;
- HYDROLOGY;
- 1830 Groundwater/surface water interaction;
- HYDROLOGY;
- 1890 Wetlands;
- HYDROLOGY;
- 4235 Estuarine processes;
- OCEANOGRAPHY: GENERAL