Irrigation performance in private urban landscapes: A study case in Zaragoza (Spain)

Irrigation water use in private landscapes represents an increasing share of total water use in semiarid areas. In this work, 102 households located in the Montecanal neighbourhood (Zaragoza, Spain) were analysed. Research took advantage of the dual water supply network (separate indoor and irrigation water networks). The analysis was based on bi-monthly water billing records for the period 2005–2007. The total household landscape area (93 m2) and the area occupied by turf, trees and shrubs were derived from aerial photographs. A method based on reference evapotranspiration was used to estimate net landscape irrigation requirements. The total average water use was 0.80 m3 household−1 day−1, with irrigation water use amounting to 46% of the total water use. Average air temperature largely determined irrigation water use (the correlation coefficient was 0.958). Overirrigation was common in the three years of study, with the average irrigation water application (IWA) being much higher than the Net Irrigation Requirements (1359 and 555 mm, respectively). Only 34% of the households showed adequate irrigation, while 6% of the households underirrigated their landscape areas. In the rest of the households (60%), overirrigation was observed. Significant time correlations were found for IWA and for an adequacy index, suggesting that landowners applied their inadequate irrigation criteria in a consistent way. Local private landscape irrigation performance was found to be very poor, probably owing to low water cost and over-the-average household income.

Research highlights
► In the households studied, landscape irrigation use amounted to 46% of the total water use.
► Indoor water use was minimum in July–August and maximum in May–June.
► Irrigation water use was determined by temperature and not influenced by precipitation peaks.
► Overirrigation was common in the three years of study, particularly in autumn.
► Households were classified according to the distance between water requirements and water application.