Advection within shallow pore waters of a coastal lagoon, Florida

• Published in: Ground water Vol. 42; no. 7; pp. 1011 - 1020
• Main Authors: Cable, J.E, Martin, J.B, Swarzenski, P.W, Lindenberg, M.K, Steward, J
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-12-2004; National Ground Water Association
• Subjects: Aquifers; Distribution; Environmental aspects; Estuaries; Groundwater flow; hydrochemistry; hydrogeology; Marine sediments; Observations; oceanography; radionuclides; radium; radon; submarine groundwater discharge; Florida; Atlantic Ocean; United States
• ISSN: 0017-467X; 1745-6584
• DOI: 10.1111/j.1745-6584.2004.tb02640.x

Ground water sources can be a significant portion of a local water budget in estuarine environments, particularly in areas with high recharge rates, transmissive aquifers, and permeable marine sediments. However, field measurements of ground water discharge are often incongruent with ground water flow modeling results, leaving many scientists unsure which estimates are accurate. In this study, we find that both measurements and model results are reasonable. The difference between estimates apparently results from the sources of water being measured and not the techniques themselves. In two locations in the Indian River Lagoon estuarine system, we found seepage meter rates similar to rates calculated from the geochemical tracers 222Rn and 226Ra. Ground water discharge rates ranged from 4 to 9 cm/d using seepage meters and 3 to 20 cm/d using 222Rn and 226Ra. In contrast, in comparisons to other studies where finite element ground water flow modeling was used, much lower ground water discharge rates of ∼0.05 to 0.15 cm/d were estimated. These low rates probably represent discharge of meteoric ground water from land‐recharged aquifers, while the much higher rates measured with seepage meters, 222Rn, and 226Ra likely include an additional source of surface waters that regularly flush shallow (< 1 m depth) sediments. This resultant total flow of mixed land‐recharged water and recirculated surface waters contributes to the total biogeochemical loading in this shallow estuarine environment.