Estuaries and Coasts

, Volume 35, Issue 5, pp 1285–1298 | Cite as

Tidal and Groundwater Fluxes to a Shallow, Microtidal Estuary: Constraining Inputs Through Field Observations and Hydrodynamic Modeling

  • Neil K. GanjuEmail author
  • Melanie Hayn
  • Shih-Nan Chen
  • Robert W. Howarth
  • Patrick J. Dickhudt
  • Alfredo L. Aretxabaleta
  • Roxanne Marino


Increased nutrient loading to estuaries has led to eutrophication, degraded water quality, and ecological transformations. Quantifying nutrient loads in systems with significant groundwater input can be difficult due to the challenge of measuring groundwater fluxes. We quantified tidal and freshwater fluxes over an 8-week period at the entrance of West Falmouth Harbor, Massachusetts, a eutrophic, groundwater-fed estuary. Fluxes were estimated from velocity and salinity measurements and a total exchange flow (TEF) methodology. Intermittent cross-sectional measurements of velocity and salinity were used to convert point measurements to cross-sectionally averaged values over the entire deployment (index relationships). The estimated mean freshwater flux (0.19 m3/s) for the 8-week period was mainly due to groundwater input (0.21 m3/s) with contributions from precipitation to the estuary surface (0.026 m3/s) and removal by evaporation (0.048 m3/s). Spring–neap variations in freshwater export that appeared in shorter-term averages were mostly artifacts of the index relationships. Hydrodynamic modeling with steady groundwater input demonstrated that while the TEF methodology resolves the freshwater flux signal, calibration of the index–salinity relationships during spring tide conditions only was responsible for most of the spring–neap signal. The mean freshwater flux over the entire period estimated from the combination of the index-velocity, index–salinity, and TEF calculations were consistent with the model, suggesting that this methodology is a reliable way of estimating freshwater fluxes in the estuary over timescales greater than the spring–neap cycle. Combining this type of field campaign with hydrodynamic modeling provides guidance for estimating both magnitude of groundwater input and estuarine storage of freshwater and sets the stage for robust estimation of the nutrient load in groundwater.


Estuarine hydrodynamics Coastal groundwater discharge Total exchange flow Estuarine modeling Index-velocity method 



Funding was provided by the USGS Coastal and Marine Geology Program and by National Science Foundation Award #0420575 from the Biocomplexity/Coupled Biogeochemical Cycles Program. Access to private property was granted by Alan Rottenberg, Michael Jackson, and Jonathan Harley. Jonathan Borden, Jennifer Thomas, Lane Boyer, and Alex Nunez performed tidal-cycle surveys with support from Marinna Martini and Christine Sabens. Rocky Geyer, Kevin Kroeger, David Ralston, Christopher Sherwood, Richard Signell, John Warner, and two anonymous reviewers provided feedback on this study and/or manuscript. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.


  1. Boesch, D.F. 2002. Challenges and opportunities for science in reducing nutrient over-enrichment of coastal ecosystems. Estuaries 25: 744–758.CrossRefGoogle Scholar
  2. Bricker, S., Longstaff, B., Dennison, W., Jones, A., Boicourt, K., Wicks, C., and Woerner, J., 2007. Effects of nutrient enrichment in the nation’s estuaries: a decade of change. NOAA Coastal Ocean Program Decision Analysis Series No. 26. National Centers for Coastal Ocean Science, Silver Spring, MD.Google Scholar
  3. Cable, J.E., W.C. Burnett, J.P. Chanton, and G.L. Weatherly. 1996. Estimating groundwater discharge into the northeastern Gulf of Mexico using radon-222. Earth and Planetary Science Letters 144: 591–604.CrossRefGoogle Scholar
  4. Costa, J.E., R.T. Cheng, F.P. Haeni, N. Melcher, K.R. Spicer, E. Hayes, W. Plant, K. Hayes, C. Teague, and D. Barrick. 2006. Use of radars to monitor stream discharge by noncontact methods. Water Resources Research 42: W07422. doi: 10.1029/2005WR004430.CrossRefGoogle Scholar
  5. Crusius, J., P. Berg, D.J. Koopmans, and L. Erban. 2008. Eddy correlation measurements of submarine groundwater discharge. Marine Chemistry 109: 77–85.CrossRefGoogle Scholar
  6. Dunne, T., and L.B. Leopold. 1978. Water in environmental planning, 95–119. New York: W.H. Freeman and Company.Google Scholar
  7. Ganju, N.K. 2011. A novel approach for direct estimation of fresh groundwater discharge to an estuary. Geophysical Research Letters 38: L11402.CrossRefGoogle Scholar
  8. Ganju, N.K., and D.H. Schoellhamer. 2006. Annual sediment flux estimates in a tidal strait using surrogate measurements. Estuarine, Coastal and Shelf Science 69: 165–178.CrossRefGoogle Scholar
  9. Ganju, N.K., D.H. Schoellhamer, and B.A. Bergamaschi. 2005. Suspended sediment fluxes in a tidal wetland: Measurement, controlling factors, and error analysis. Estuaries 28: 812–822.CrossRefGoogle Scholar
  10. Ganju, N.K., Dickhudt, P.J., Thomas, J.A., Borden, J., Sherwood, C.R., Montgomery, E.T., Twomey, E.R., and Martini, M.A., 2011, Summary of oceanographic and water-quality measurements in West Falmouth Harbor and Buzzards Bay, Massachusetts, 2009–2010: Open-File Report 2011–1113, CD-ROM. Also available at
  11. Howarth, R.W. 2008. Coastal nitrogen pollution: A review of sources and trends globally and regionally. Harmful Algae 8: 14–20.CrossRefGoogle Scholar
  12. Howes, B., Kelley, S.W., Ramsey, J.S., Samimy, R., Schlezinger, D., and Eichner, E., 2006. Linked watershed-embayment model to determine critical nitrogen loading thresholds for West Falmouth Harbor, Falmouth, Massachusetts. Massachusetts Estuaries Project: Massachusetts Department of Environmental Protection, Boston, Massachusetts, 161 p.Google Scholar
  13. Knudsen, M. 1900. Eine hydrographische Lehrsatz. Annalen der Hydrographie und Marinen Meteorologie 28: 316–320.Google Scholar
  14. Kroeger, K.D., M.L. Cole, J.K. York, and I. Valiela. 2006. Nitrogen loads to estuaries from waste water plumes: modeling and isotopic approaches. Groundwater 44: 188–200.CrossRefGoogle Scholar
  15. Kroeger, K.D., P.W. Swarzenski, W.J. Greenwood, and C. Reich. 2007. Submarine groundwater discharge to Tampa Bay: Nutrient fluxes and biogeochemistry of the coastal aquifer. Marine Chemistry 104: 85–97.CrossRefGoogle Scholar
  16. LeBlanc, D.R., Guswa, J.H., Frimpter, M.H., and Londquist, C.J., 1986. Ground-water resources of Cape Cod, Massachussetts. U.S. Geological Survey Hydrologic Atlas 692.Google Scholar
  17. Lee, D.R. 1977. A device for measuring seepage flux in lakes and estuaries. Limnology and Oceanography 22: 140–147.CrossRefGoogle Scholar
  18. MacCready, P. 2011. Calculating estuarine exchange flow using isohaline coordinates. Journal of Physical Oceanography 41: 1116–1124.CrossRefGoogle Scholar
  19. MacCready, P., and W.R. Geyer. 2010. Advances in estuarine physics. Annual Reviews of Marine Science 2: 35–58.CrossRefGoogle Scholar
  20. McGlathery, K.J., K. Sundback, and I.C. Anderson. 2007. Eutrophication in shallow coastal bays and lagoons: The role of plants in the coastal filter. Marine Ecological Progress Series 348: 1–18.CrossRefGoogle Scholar
  21. Moore, W.S. 1996. Large groundwater inputs to coastal waters revealed by 226Ra enrichments. Nature 380: 612–614.CrossRefGoogle Scholar
  22. Mueller, D.S., and Wagner, C.R., 2009. Measuring discharge with acoustic Doppler current profilers from a moving boat. U.S. Geological Survey Techniques and Methods 3A–22, 72 p.Google Scholar
  23. National Research Council. 2000. Clean coastal waters: Understanding and reducing the effects of nutrient pollution, 391. Washington: National Academy Press.Google Scholar
  24. Nixon, S.W., B. Buckley, S. Granger, and J. Bintz. 2001. Responses of very shallow marine ecosystems to nutrient enrichment. Human and Ecological Risk Assessment 7: 1457–1481.CrossRefGoogle Scholar
  25. Pawlowicz, R., B. Beardsley, and S. Lentz. 2002. Classical tidal harmonic analysis including error estimates in MATLAB using T_TIDE. Computers & Geosciences 28: 929–937.CrossRefGoogle Scholar
  26. Penman, H.L. 1948. Natural evaporation from open water, bare and grass. Proceedings of the Royal Society of London, Ser. A 193: 120–145.CrossRefGoogle Scholar
  27. Portnoy, J.W., B.L. Nowicki, C.T. Roman, and D.W. Urish. 1998. The discharge of nitrate-contaminated groundwater from developed shoreline to marsh-fringed estuary. Water Resources Research 34: 3095–3104.CrossRefGoogle Scholar
  28. Ruhl, C.A., and Simpson, M.R., 2005. Computation of discharge using the index-velocity method in tidally affected areas. U.S. Geological Survey Scientific Investigations Report 2005–5004. Available at
  29. Shuttleworth, W.J. 1993. Evaporation. In Handbook of hydrology, ed. D.R. Maidment, 4.1–4.53. New York: McGraw-Hill.Google Scholar
  30. Simpson, M.R., and R. Bland. 2000. Methods for accurate estimation of net discharge in a tidal channel. Institute of Electrical and Electronics Engineers Journal of Oceanic Engineering 25: 437–445.Google Scholar
  31. Simpson, M.R., and Oltmann, R.N., 1993. Discharge-measurement system using an acoustic Doppler current profiler with applications to large rivers and estuaries. U.S. Geological Survey Water-Supply Paper 2395, 32 p. Available at
  32. Taylor, J.R. 1997. An introduction to error analysis, 2nd ed. Sausalito: University Science.Google Scholar
  33. Valiela, I., J. Costa, K. Foreman, J.M. Teal, B. Howes, and D. Aubrey. 1990. Transport of groundwater-borne nutrients from watersheds and their effects on coastal waters. Biogeochemistry 10: 177–197.CrossRefGoogle Scholar
  34. Wagner, R.J, Boulger, R.W., Jr., Oblinger, C.J., and Smith, B.A., 2006. Guidelines and standard procedures for continuous water-quality monitors: station operation, record computation, and data reporting. U.S. Geological Survey Techniques and Methods 1-D3, 51 p.Google Scholar
  35. Warner, J.C., C.R. Sherwood, H.G. Arango, and R.P. Signell. 2005. Performance of four turbulence closure models implemented using a generic length scale method. Ocean Modelling 8: 81–113.CrossRefGoogle Scholar
  36. Warner, J.C., C.R. Sherwood, R.P. Signell, C.K. Harris, and H.G. Arango. 2008. Development of a three-dimensional, regional, coupled wave, current, and sediment-transport model. Computers & Geosciences 34: 1284–1306.CrossRefGoogle Scholar

Copyright information

© Coastal and Estuarine Research Federation (outside the USA) 2012

Authors and Affiliations

  • Neil K. Ganju
    • 1
    Email author
  • Melanie Hayn
    • 2
  • Shih-Nan Chen
    • 3
  • Robert W. Howarth
    • 2
  • Patrick J. Dickhudt
    • 1
  • Alfredo L. Aretxabaleta
    • 1
  • Roxanne Marino
    • 2
  1. 1.U.S. Geological Survey, Woods Hole Coastal and Marine Science CenterWoods HoleUSA
  2. 2.Department of Ecology and Evolutionary BiologyCornell UniversityIthacaUSA
  3. 3.National Taiwan University, Institute of OceanographyTaipeiTaiwan

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