Monitoring irrigation performance in Esfahan, Iran, using NOAA satellite imagery

Performance of four irrigation systems in the Zayandeh Rud Basin, Esfahan, Iran, was assessed for the systems as a whole, rather than on only official registered water extractions and uses. NOAA satellite images were analyzed using the SEBAL (surface energy balance algorithm for land) algorithm to obtain actual and potential evapotranspiration and biomass production. The missing term in the water balance was used to estimate groundwater extractions and unaccounted extraction from the river. For Abshar-Left groundwater extraction surpassed surface water applications, while for Nekouabad-Left groundwater extractions were very low. For Abshar-Right a large amount of water was pumped directly out of the river. The assessment of the systems was expressed by the productivity of water, defined as kg biomass over m3 water evaporated. Productivity was higher (∼0.72 kg m−3) for the systems relying on surface water (Nekouabad-Left and Abshar-Right) than for the conjunctive systems, reflecting the difference in water quality between groundwater and surface water. Finally, it was concluded that the advantages of the methodology presented here over the traditional assessments are: (i) most data is readily available, (ii) all water users are included, (iii) groundwater extraction can be estimated, and (iv) a real time assessment can be setup using this approach.