Abstract
Meteorological data from vegetated and un-vegetated wetlands during wet and dry seasons, were collected and analyzed to evaluate the role of wind and vegetation on wetlands’ hydrology. Wind speed diminished by as much as 40%, accompanied by a measurable change in wind directions in the vegetated compared to the open water site. Wind speed and direction means were significantly different (p < 0.001 and <0.01), for vegetated and non-vegetated wetland, respectively. Cattails (Typha sp.) and open water estimates of wind drag coefficients using the log wind profile, were 0.016 and 0.009 for dry season, and 0.012 and 0.005 for wet season, respectively. Wind set up near the wetland outlet was more pronounced at shallow water depth (<20 cm). Measured velocity profile during inflow discharge event with a wind speed of 0.53 ms−1, showed two-layer flows; wind-generated surface water flow opposite to a sub-surface inflow. This opposing surface flow increases hydraulic residence time and improve nutrient uptake. Conversely, wind-generated flows aligned with inflow discharges, accelerates water flow towards the outlet, reduce the duration of water-biotic interactions, and decrease nutrient uptake.
Highlights
Aquatic vegetation is an integral part of all natural and constructed wetlands and plays a vital role in treating both urban and agricultural runoff as well as wastewater
We found no major differences in results obtained for the aforementioned parameters, due to presence or absence of emergent vegetation at the two wetland cells
Similar to vegetation resistance to water movement in the water column induced by the presence of aquatic vegetation [24,30], emergent vegetation in this experiment, induced resistance to air flow and impacts the frequency of wind classes compared to open water site
Summary
Aquatic vegetation is an integral part of all natural and constructed wetlands and plays a vital role in treating both urban and agricultural runoff as well as wastewater. Aquatic plants assimilate nutrients for growth and reproduction, provide surface area for microbial growth, stabilize the soil, act as a filter to trap submerged detritus and sediment, induce resistance to flow, and decrease the ability of the water to carry sediments [1,2,3,4,5]. In south Florida, permanent features such as above ground reservoirs (flow equalization basin (FEB)) and large constructed wetlands (stormwater treatment area (STA)) are used to store and remove phosphorus (P) from stormwater runoff. The key role of aquatic vegetation in both features is to remove phosphorus from agriculture runoff to acceptable levels before water is released southward into the Northern Everglades. The presence of EAV in those features induce resistance to flow, which causes delays of water deliveries within and in-between features [7]
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