Using OpenET Platform and LI-710 Sensor for Irrigation Management in Arizona

Abstract

While freshwater is renewable, water resource depletion is occurring considerably more quickly than expected. With population growth and socioeconomic development, global water consumption has increased nearly sevenfold in the last century (Gleick, 2000), impacting the long-term sustainability of agriculture. The agriculture sector, the largest water user, accounts for over two-thirds of withdrawals. Therefore, precise irrigation is vital in arid regions where agriculture uses a significant share of water resources. Crop evapotranspiration (ETc) accounts for most of irrigation water use, especially in dry climates. Thus, accurate ETc estimation is important. Different methods are used to estimate ETc, such as lysimeters, Bowen ratio, surface renewal, and eddy covariance (EC), but they are costly and require expertise (Elsadek et al., 2025). Remote sensing models can also be used to estimate ETc, but their applications are limited by cost, expertise, and computational requirements (Volk et al., 2024). Recently, the OpenET platform has been developed to offer free, high-resolution ET data suitable for US irrigation management. The LI-710 sensor (LI-COR Inc., Lincoln, Nebraska, USA) was also presented as a lower-cost, user-friendly alternative to EC systems, providing continuous ETc measurements with less maintenance. Limited studies evaluated OpenET for irrigated alfalfa in Arizona; however, no cited studies evaluated OpenET or LI-710 for late-planted cotton in Arizona (Attalah et al., 2025, 2024). The following guide leverages a field study that cross-validates cotton ET from OpenET and LI-710 against soil water balance (SWB) estimates in Gila Bend, Arizona, aiming to identify the best technique for estimating cotton ET for irrigation management under arid conditions.