No abstract

No abstract

No abstract

Freshwater input to estuaries may be greatly altered by the river barrages required to meet human needs for drinking water and irrigation and prevent salt water intrusion. Prior studies have examined the salt plugs associated with evaporation and salt outwelling from tidal salt flats in single-channel estuaries. In this work, we discovered a new type of salt plug formation in the multi-channel Pasur River Estuary (PRE) caused by decreasing river discharges resulting from an upstream barrage. The formation of a salt plug in response to changes in river discharge was investigated using a conductivity-temperature-depth (CTD) recorder during spring and neap tides in the dry and wet seasons in 2014. An exportation of saline water from the Shibsa River Estuary (SRE) to the PRE through the Chunkhuri Channel occurred during the dry season, and a salt plug was created and persisted from December to June near Chalna in the PRE. A discharge-induced, relatively high water level in the PRE during the wet season exerted hydrostatic pressure towards the SRE from the PRE and thereby prevented the intrusion of salt water from the SRE to the PRE.

[1] The thermal properties of sediment and the albedo are critical in calculating the heat flux of a tidal flat. However, they are not well known because of the difficulties of sampling and observing tidal flats. We use extensive field observations of a macrotidal flat on the western coast of Korea to determine its sediment heat capacity and albedo. The estimated heat capacity of the upper 0.1 m is 3.65 Â 10 6 J m À3 K À1 with a water content of 70%. Heat capacity decreases with depth to 2.96 Â 10 6 J m À3 K À1 at 0.4 m depth. Estimated thermal diffusivities are 0.47-0.63 Â 10 À6 m 2 s À1 and 0.38-0.64 Â 10 À6 m 2 s À1 in spring and summer, respectively. The calculated albedo is a strong function of the solar altitude and the atmospheric transmittance. Atmospheric transmittance is especially important to the albedo when the solar altitude is low. Seasonal mean albedos are 0.13 and 0.15 in spring and summer, respectively. The heat capacity and albedo values obtained above were verified by using them to make independent heat flux estimates at other stations. Estimates based on heat capacity were correlated to albedo-based heat flux estimates with an r 2 greater than 0.7.