Assessment of aquatic plants evapotranspiration for secondary agriculture drains (case study: Edfina drain, Egypt)

This research was set in order to estimate aquatic plants evapotranspiration, (ET) in Edfina drain, Nile Delta, Egypt, which had an in-stream treatment wetland that was taken as a case study. A simple field scale approach is presented to measure drain water evaporation and water consumption of five aquatic plants, cultivated in floating tanks. Plants ET, (ETp) values were obtained by measuring the daily quantity of water required to renovate the tank’s initial volume. Crop coefficients (Kc) were obtained and water loss from the drain wetland was calculated due to evaporation and plants cells ETp. Results presented values of ETp and Kc which were controlled by plant leaf area and growing stage. The major ETp was for Hyacinth followed by Cattail, Reeds, Torpedo grass, and then duckweeds. All ETp values exceeded twice the adjacent non-vegetated water evaporation. The obtained Kc values referenced to the drain water evaporation were almost twice the Kc values of FAO Penman–Monteith ET, due to the landscape effects, as hot dry air can cause extra heat input and water loss. Total losses from in-stream treatment series of pond, 4 plants reaches and open disinfection zone did not exceed 0.55% of drain discharge.