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

Abstract

Estimation of the Crop Evapotranspiration (ET_C) 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.

Keywords:

• crop coefficient
• Penman-Monteith
• wastewater treatment
• hydrological modeling