Developing Water Balances of Ornamental Landscapes

Landscape irrigation represents a major portion of the potable water use in arid and semi-arid regions (30-70% in Intermountain West). Therefore, there is considerable potential for water savings through conservation in the landscape. Using plant species that require less water is one important principle of XeriscapingTM, but little research has been done to investigate the water requirements of water efficient landscapes differing only in plant materials. Nine landscapes were installed in large, drainage lysimeters with three classes of plant material: traditional (high water use), intermediate (moderate water use), and native/adapted plant species of the Intermountain West (low water use). Each plot was divided into three irrigation zones: shrub, turf and perennial. In each zone, 4 Acclima™ soil moisture sensors were installed at 80, 45, 20, and 5-cm depths. Sensors measured soil volumetric water content and electrical conductivity, representing soil layers between 100 to 60, 60 to 30, 30 to 10 and 10 to 0-cm, every hour. Three plots (one for each landscape type) were chosen as master plots, and sensors at different depths in each zone of master plots were used to control irrigation. Leachate from each landscape was quantified using dippers connected a Campbell Scientific™ CR1000 data logger. Water balances for each irrigation zone were developed using the water balance equation (Total ET= DW + Precipitation + Irrigation–Leachate), and allowed comparisons to be made of the water requirements of different plant materials in landscapes. Furthermore, water balances were developed for each plot to investigate the overall water requirements for the three landscape types.