Estimating Water Consumption and Irrigation Requirements in a Long-Established Mediterranean Rural Community by Remote Sensing and Field Data

The present study illustrates an original methodology for estimating irrigation requirements and quantifying real water consumption in a long-established Mediterranean rural community (Delta Llobregat, Barcelona, Spain), combining data from remote sensing, field mapping and in situ measurements. Because of land fragmentation and crop diversification, SPOT-5 imagery was used, given its spatial and temporal resolution and spectral attributes. Simultaneously, four flow meters were installed in two representative locations to measure water inputs and outputs every 5 min. Conveyance and irrigation efficiency were estimated for the entire irrigation community. The average conveyance efficiency was 46.8% and the classical and net irrigation efficiency reached 26.4 and 59.8%, respectively, with half of the water volume (55% or 3.2 hm³) returned to the river or diverted to wetlands, the maximum percentage of estimated error being about 3.4%. These results indicate an exceptionally high water loss rate due to the irrigation system (flooding), the ageing conveyance network and urban infrastructure breakdown. The applied protocol proved useful for monitoring low-efficiency irrigation systems in small communities experiencing intense urban and industrial pressures.