Evapotranspiration increases during summer due to ambient air temperature. This will be affecting effluent water temperature in vegetated constructed wetland but either increasing or decreasing. If anyone could explain this.
I am not sure reena if the evapotranspiration should substantially effect effluent water temp. However, effluent water temp should be affected by land surface temperature, evapotranspiration usually cannot affect LST or water surface temperature to any reasonable degree.
To help you finding an answer, i would like to add that, evapotranspiration increases in summer not only because of higher ambient temperature, but also may be more importantly due to lower relative humidity i.e. higher VPD, and if available higher wind speed...
Very interesting question, Reena.
Let me speculate: evapotranspiration has to cool the surfaces, where it occurs - but not the water body from where water for evapotranspiration is taken. Evapotransiration is likely to reduce the volume of the effluent water - increasing the surface to volume ratio and thus water temperature. On the other hand increasing water vapor above the water surface may reduce the amount of solar radiation reaching the water surface..
My guess is, that evapotranspiration may lead to slightly increased water temperature. Are you planning a project?
kind regards
Irene
Thanks Irene
Actually I found temperature reduction in outlet water of constructed wetland microcosm during summer. I thought evapotranspiration could be one of the reason behind it.
@Reena, this is very interesting. As far as I know nothing is published on the subject. You could run an experiment with several microcosms measuring air and water temperature, humidity and irradation on several locations and get the results published. You´ll have to role out other explanations, especially effects of shading, though.
best wishes, Irene
You can find detalied information about evaporation, evapotranspiration and crop water use in FAO Paper No 56, by Allen et al.
In vegitated wetland system, lesser incoming solar radiation into the waterbody due to presence of upper vegitation, will lead to lower water temperature compared to other waterbodies. But no clear idea about your specific question on evapotranspiration.!!!
Wetlands typically cool water by two methods: (1) vegetation blocks solar radiation and keeps water in wetlands cooler than water that is not vegetated and (2) in order for water to evaporate, (kinetic) energy is lost and thus cooling occurs. When plants transpire, evaporative cooling occurs. Therefore, effluent should be cooler than the water that is entering a constructed wetland.
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