Quantifying the trade-off between landscape vegetation height, surface temperature, and water consumption in single-family residential houses for a desert city.

In light of climate change and urban sustainability concerns, researchers have been studying how residential landscape vegetation affect household water consumption and heat mitigation. Previous studies have analyzed the correlations among residential landscape practices, household water consumption, and urban heating at aggregate spatial scales to understand complex landscape decision tradeoffs in an urban environment. This research builds upon those studies by using parcel-level variables to explore the implications of vegetation quantity and height on water consumption and summertime surface temperatures in a set of single-family residential homes in Tempe, Arizona. QuickBird and LiDAR vegetation imagery (0.600646m/pixel), MASTER temperature data (approximately 7m/pixel), and household water billing data were analyzed. Findings provide new insights into the distinct variable, vegetation height, thereby contributing to past landscape studies at the parcel-level. We hypothesized that vegetation of different heights significantly impact water demand and summer daytime and nighttime surface temperatures among residential homes. More specifically, we investigated two hypotheses: 1) vegetation greater than 1.5 m in height will decrease daytime surface temperature more than grass coverage, and 2) grass cover will increase household water consumption more than other vegetation classes, particularly vegetation height. Bivariate and stepwise linear regressions were run to determine the predictive capacity of vegetation on surface temperature and on water consumption. Trees of 1.5m-10m height and trees of 5m-10m height lowered daytime surface temperatures. Nighttime surface temperatures were increased by trees of 5m-10m height and decreased by grass. Houses that experienced higher daytime surface temperatures consumed less water than houses with lower daytime surface temperatures, but water consumption was not directly related to vegetation cover or height. Implications of this study support the practical application of tree canopy (vegetation of 5m-10m height) to mitigate extreme surface temperatures. The trade-offs between water and vegetation classes are not yet clear because vegetation classes cannot singularly predict household water consumption.