Evapotranspiration of the Vetiver and Tifton 85 grasses grown in horizontal subsurface flow constructed wetlands

摘要

Estimation of the Crop Evapotranspiration (ETC) in Horizontal Subsurface Flow Constructed Wetlands (HSSF-CWs) is of great importance for hydrological modeling of these systems. The objective of this work was to obtain the Crop Coefficient (K-C) values of Vetiver (Chrysopogon zizanioides) and Tifton 85 (Cynodon spp.) grasses when grown in HSSF-CWs whose porous medium was saturated with solutions containing different nutrients concentrations. The water balance was performed every day in order to determine the K-C of the grasses. It was verified that the K-C values of the Vetiver grass were independent of the nutrient availability, expressed in terms of Electrical Conductivity (EC) of the nutrient solution. The K-C value in the initial growth phase (Phase I) was 0.99, independent of the seasons. In Phase II, the K-C were 0.95 and 1.36 for autumn and spring, respectively, and for Phase III were 1.12 in autumn and 1.60 in spring. In relation to the Tifton 85 grass, the K-C values showed a quadratic behavior as a function of the EC, where the K-C estimation models were obtained by the cluster analysis in Phase II and III. For Phase I, the K-C value was 1.17, independent of the EC and the time of year.