Transpiration effect of Tufted sedge for a horizontal subsurface flow constructed wetland

Abstract

We studied water loss performance in a model plant, the Tufted sedge (Carex elata All.), which is an active water balance component of subsurface flow constructed wetlands. Due to active regulation of transpiration, the volume and dynamics of water loss in these constructed wetlands are difficult to plan without preliminary and targeted measurements and calculations with regard to the specific plant component. We estimated transpiration values in the laboratory based on daytime transpiration ranges for spring, summer and autumn, and examined the transpiration effect of the hydraulic load. During spring, water loss via transpiration can reach 83% of the hydraulic load on certain days. During summer, this value can increase to 100% of the hydraulic load, which means that the daytime transpiration can significantly affect effluent concentration. Air humidity proved to be the most critical environmental factor for water loss resulting from transpiration, therefore a water discharge plan designed in such a way as to be able to also adjust soil moisture is the key to optimal water circulation at the system level.

Estimated seasonal daily evapotranspiration rates for a horizontal subsurface flow constructed wetland

“…The values were 13.6-22.7 mm/day in autumn, which is 34.0-56.8% of the maximum hydraulic load. These values are similar to those of Dittrich et al [30] There were days when the morning and evening condensation were very high causing significant increase in water level. This has two consequences, on the one hand, condensed vapor increases the water level supplying the constructed wetland, on the other hand, due to humidity of around 100%, evapotranspiration is slightly reduced.…”

“…It follows that the concentration processes caused by evapotranspiration were 4-10 times more potent during daytime than nighttime in this constructed wetland. -The evapotranspiration at night is significant, as there are some days when the total, daily water loss via evapotranspiration is 21.0-28.0 % of the total daily water loss, these values are similar to Dittrich et al [30]. -There were days when the condensation values were high, consequently, the daytime and nighttime ratio could not be divided.…”