TESTING THE VARIABILITY OF WATER ABSORPTION IN AN EXTENSIVE GREEN ROOF WITH AN IRRIGATION SYSTEM

The implementation of a drip irrigation system to an extensive green roof is considered to be an attractive sustainable design for a residential building. In this study, the performance of a drip irrigation system in a green roof was determined by measuring the significance in variability of water absorption.To do this, random samples of the soil medium were gathered to a depth of 2 cm., first layer. The soil medium consisted of three layers: 1 Soil mixture at 2 cm depth (40% peat, 40% organic, and 20% silt), 2 Silt from 2-4 cm depth, and 3 Soil mixture from 4-8 cm depth (40% peat, 40% organic, and 20% silt). Two techniques for determining the water absorption were evaluated, being a soil moisture sensor and the “Standard Test Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass.” This experiment was conducted in a full-scale green roof with a drip irrigation system installed. The purpose for conducting this study was to test the effectiveness of a self design drip irrigation system on a green roof. Finally, to assure a consistent Bowen ratio and a low conductive heat fluxes according to Gaffin et al. (2006) and Tabares-Velasco (2009).

There is no strong evidence of a linear regression between water absorption and irrigation intervals through time due to a low coefficient of determination (r²) of 0.064 (Townend, 2002). Value tells us that only 6% of the total variation of water absorption can be attributed to successive irrigation intervals (Berk, 2010). The ratio given by dividing the between-group variance by the within-group variance gives an F test value approximately equal to one (F=0.636). This indicates that there is no difference means since both, between and within, variances are approximately the same (Bluman, 2008). We can point out that sample means give a good representation of the total population.

There is no significant difference between and within any of the irrigated intervals and there is enough evidence to support the claim that there are equal means of water absorption trough time. We can assume that the irrigation system creates a homogeneous moisture distribution during every application of water on the surface layer of this green roof. This said a consistent Bowen ratio and a low conductive heat fluxes is expected according to Gaffin et al. (2006) and Tabares-Velasco (2009).