Spatio-temporal variation of reference evapotranspiration from empirical methods in Chihuahua, Mexico

<strong>Introduction:</strong> Evapotranspiration is key in the management of arid agricultural areas. In Chihuahua, volume irrigation water based on reference evapotranspiration (ET<sub>o</sub>) calculated with empirical methods and extrapolated to cropped area, which inaccurate. The alternative calculate ET<sub>o</sub> variation by spatial interpolation.</br> <strong>Objective:</strong> To analyze spatio-temporal using interpolation Mexico.</br> <strong>Methodology:</strong> Records from 33 meteorological stations 1960-2013 seven estimation were used. results compared Penman-Monteith method, modified FAO (PMMF), ANOVA analysis (P ≤ 0.05), homogeneous surfaces built point values <strong>Results:</strong> Hargreaves method (R<sup>2</sup> = 0.91, RMSE 1.16 ME -0.69 mm-day<sup>-1</sup>) had a smaller bias respect PMMF. ranged 2.5 7.1 mm-day<sup>-1</sup> west-east direction, maximum at low elevations minimum high elevations, showed influence Sierra Madre Occidental ET<sub>o</sub>. This characteristic was most noticeable warm months (June September).</br> <strong>Limitations study:</strong> use estimated data needs field validation.</br> <strong>Originality:</strong> one extrapolate areas scarce data.</br> <strong>Conclusions:</strong> allows estimating large extensions limited information.</br>