Impact of exchange flows on wetland flushing

Abstract

Abstract. The flushing of littoral regions is governed by barotropic river flows, Q R, and baroclinic exchange flows, AQ. This note presents field observations of two different flushing regimes in a shallow wetland that borders a lake. In spring, when river flows arc high, the wetland circulation is river-or jet-dominated, AQ/QR < 1, and the river shortcircuits through the wetland in a much shorter time than the nominal residence time. During summer low flows, however, the wetland circulation is dominated by exchange flows, AQ/Q• > 1, that vary both on diurnal and synoptic (10-20 days) timescales in response to differential heating and cooling between the wetland and lake and to wind. These exchange flows can enhance wetland flushing by a factor of 10 relative to river flushing. A one-dimensional d½couplcd heat and flow model represents diurnal exchange flows in this system well and may be used to assess the importance of exchange flows in other systems.

Solute transport and storage mechanisms in wetlands of the Everglades, south Florida

“…Field‐based measurements of solute transport in wetlands are relatively few [ Nepf , 1997, 1999; Andradottir and Nepf , 2001; Martinez and Wise , 2003; Keefe et al , 2004]. Most previous tracer experiments in wetlands have taken place either in coastal systems [ Harvey et al , 1995; Nepf , 1999; Tobias et al , 2001], or in wetlands constructed for water treatment [ Schulz and Peall , 2001; Martinez and Wise , 2003; Keefe et al , 2004].…”

“…[4] Field-based measurements of solute transport in wetlands are relatively few [Nepf, 1997[Nepf, , 1999Andradottir and Nepf, 2001;Martinez and Wise, 2003;Keefe et al, 2004].…”

Summer water circulation in Frenchman's Bay, a shallow coastal embayment connected to Lake Ontario

“…Such temperature gradients can arise due to the differential heating and cooling of shallow water bodies (Monismith et al, 1990;Andradóttir and Nepf, 2001;Wells and Sherman, 2001). In studies of deep coastal embayments of Lake Ontario, these temperature driven exchange flows have been found to be the dominant water exchange process during the summer (Lawrence et al, 2004;Rueda and Cowen, 2005), rather than the flows due to short term water level fluctuations.…”

Determinants of temperature in small coastal embayments of Lake Ontario

“…In the Great Lakes, exchanges between the connected lake and the embayment are driven primarily by horizontal temperature or density gradients and seiche-driven changes in water level (Hamblin and He, 2003;Lawrence et al, 2004;Rueda and Cowen, 2005;Wells and Sealock, 2009). Horizontal temperature gradients establish because shallow embayments and the deeper Great Lakes have large differences in their thermal inertia (Andradóttir and Nepf, 2001;Monismith et al, 1990;Wells and Sherman, 2001). The extent of the thermal gradient varies according to local meteorological and atmospheric conditions and the occurrence of episodic cold water upwelling or warmer downwelling events (Boyce et al, 1989;Csanady, 1977;Haffner et al, 1984;Plattner et al, 2006;Rueda and Cowen, 2005).…”