Hydrology in tidal creeks


Block diagram of hydrology in tidal creeks

Hydrology processes in tidal creeks

1. Catchment freshwater input

Very little freshwater enters from the catchment, which itself may be very small. The quantity of freshwater input can vary seasonally, depending on regional climatic conditions, however is, by definition, very low in tidal creeks. Tidal creeks lack distinct river or creek input channels, and receive freshwater from sheet runoff only. Groundwater input may also be a significant source of freshwater.

2. Tidal mixing

Tidal creeks typically exhibit very well-mixed water circulation conditions, due to the mixing effect of strong tidal currents. Circulation processes are complicated by the massive system of intricate dendritic drainage (Wolanski et al., 1992). Mixing regimes may also vary seasonally (Eyre, 1998, Digby et al., 1996). Salinity is homogenous throughout the channels, and due to the limited input of freshwater, stratification does not occur. The tidal range within tidal creeks may be amplified in comparison to the adjacent coastal ocean (depending on the geometry of the channel), and tides also tend to penetrate further inland with increasing tidal range.

3. Hypersaline groundwaters

Saltflat environments are rarely inundated (e.g. 3-4 days per month), resulting in hypersaline groundwaters and often a saline crust on the surface (Ridd et al., 1997).

4. Exchange of marine water

Exchange of marine water occurs through the wide entrance of the tidal creek. Flood and ebb tides may follow different routes into and out of the tidal creek, and the volume of the tidal prism tends to be large (Wolanski, 1986b).

5. Evaporation

Evaporation is a significant process in tidal creeks due to the extensive intertidal area (also depending on climatic conditions). Hypersaline conditions may occur (particularly in arid regions) if dry weather conditions continue for a long period (Heggie et al., 1999b, Yassini et al., 1995), however due to mixing this typically does not cause significant stratification.