Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
Hydrol. Earth Syst. Sci., 21, 4563-4572, 2017
https://doi.org/10.5194/hess-21-4563-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
13 Sep 2017
Spatiotemporal variation of Van der Burgh's coefficient in a salt plug estuary
Dinesh Chandra Shaha1,2, Yang-Ki Cho2, Bong Guk Kim2, M. Rafi Afruz Sony1, Sampa Rani Kundu3, and M. Faruqul Islam4 1Department of Fisheries Management, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur 1706, Bangladesh
2School of Earth and Environmental Science/Research Institute of Oceanography, Seoul National University, Seoul, Korea
3Deparment of Oceanography, Chonnam National University, Gwangju, Korea
4Hydrography Division, Mongla Port Authority, Bagherhat, Bangladesh
Abstract. Salt water intrusion in estuaries is expected to become a serious global issue due to climate change. Van der Burgh's coefficient, K, is a good proxy for describing the relative contribution of tide-driven and gravitational (discharge-driven and density-driven) components of salt transport in estuaries. However, debate continues over the use of the K value for an estuary where K should be a constant, spatially varying, or time-independent factor for different river discharge conditions. In this study, we determined K during spring and neap tides in the dry (< 30 m−3 s−1) and wet (> 750 m−3 s−1) seasons in a salt plug estuary with an exponentially varying width and depth, to examine the relative contributions of tidal versus density-driven salt transport mechanisms. High-resolution salinity data were used to determine K. Discharge-driven gravitational circulation (K ∼ 0.8) was entirely dominant over tidal dispersion during spring and neap tides in the wet season, to the extent that salt transport upstream was effectively reduced, resulting in the estuary remaining in a relatively fresh state. In contrast, K increased gradually seaward (K ∼ 0.74) and landward (K ∼ 0.74) from the salt plug area (K ∼ 0.65) during the dry season, similar to an inverse and positive estuary, respectively. As a result, density-driven inverse gravitational circulation between the salt plug and the sea facilitates inverse estuarine circulation. On the other hand, positive estuarine circulation between the salt plug and the river arose due to density-driven positive gravitational circulation during the dry season, causing the upstream intrusion of high-salinity bottom water. Our results explicitly show that K varies spatially and depends on the river discharge. This result provides a better understanding of the distribution of hydrographic properties.

Citation: Shaha, D. C., Cho, Y.-K., Kim, B. G., Sony, M. R. A., Kundu, S. R., and Islam, M. F.: Spatiotemporal variation of Van der Burgh's coefficient in a salt plug estuary, Hydrol. Earth Syst. Sci., 21, 4563-4572, https://doi.org/10.5194/hess-21-4563-2017, 2017.
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In this work, Van der Burgh's coefficient, K, is determined in the dry and wet seasons in a salt plug estuary to examine the contributions of tidal versus density-driven salt transport mechanisms. Gravitational circulation was entirely dominant over tidal dispersion in the wet season, whereas density-induced inverse and positive gravitational circulation facilitated an inverse and a positive estuarine circulation seaward and landward from the salt plug area during the dry season, respectively.
In this work, Van der Burgh's coefficient, K, is determined in the dry and wet seasons in a salt...
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