Living green walls: Estimation of water requirements and assessment of irrigation management

Abstract

Most studies of living green walls (LGWs) address their benefits in enhancing vegetative cover and irrigation levels. However, few have focused on the estimation of corresponding water and irrigation management requirements. These issues are addressed in this work in reference to substrate, physical and hydraulic properties and irrigation systems.The studied LGW is located in the itd-UPM building (Madrid) and was studied for 109 days.This paper measures the annual water consumption of this LGW and its plant phenology cycle while adapting methodologies to agricultural crops and to traditional urban gardening methods based on 4 months of daily data collection.The landscape coefficient (KL) was calculated as the rate between the measured values of real and reference evapotranspiration and as real evapotranspiration and was estimated with the WUCOLS III method. We obtained a KL-curve of 0.32 (for the winter) to 0.6 (for the summer) based on the three components of the KL (species Ks, microclimate Kmc and planta density coefficient Kd).From these results, one can schedule LGW irrigation in a more optimal manner than methods traditionally used, which are based on trial and error.Appropriate irrigation design, operation and irrigation management was assessed by measuring the substrate water content (θ) distribution around the LGW and by analyzing differences with an ANOVA and Tukey’s honestly significant difference test.LGW irrigation involved a combination of drip irrigation and percolation, producing a border effect and resulting in the development of two hydro zones: one located in the upper LGW (12% of the total area) with a water deficit and the other located at the base (88% of the total area) with a high θ and prone to root asphyxia water. Both are in a fragile equilibrium and can be maintained or improved upon by following the recommendations given in this paper.