What data is required to calculate a landscape water budget?

• A. ET + Total Area
• B. Plant Factor + ET
• C. Plant Factor + ET + Total Area
• D. Total Area only

Answer: (C)

To estimate a landscape water budget, you need to turn a rate of water loss into a total volume for the whole landscape. Evapotranspiration (ET) tells you how much water is lost per unit area over time, but landscapes often have a mix of plants that use water differently, which is captured by the Plant Factor. By applying the Plant Factor to ET, you get the actual landscape ET rate (ETc) for the plant mix. Then you multiply that rate by the Total Area to convert from a per-area rate to a total volume for the entire landscape. So the data needed are Plant Factor, ET (to form ETc), and Total Area. Without any one of these, you can’t accurately compute the total water use for the landscape.