Alternative solution for determining the irrigation water quantity: ET<sub>Gauge</sub>

Measuring the reference evapotranspiration (ET0) isdifficult and costly. Some regions can have variable microclimates and these can often bequite far from climate stations. Therefore, itis optimal touse local measurements rather than aregionally calculated ET0. Inthis respect, one piece ofequipment that provides cheap and reliable measurement results isETGaugeequipment. Inthis study, ET0values measured with ETGaugeequipment were compared with daily and monthly ET0values calculated byfive different commonly used empirical methods (ThornthwaiteAdj, Blaney-Criddle, Penman-Monteith = PM, Jensen-Haise and ASCE standardised Penman-Monteith = ASCE SZ PM). During the measurement period, daily ET0values measured with ETGaugevaried between 0–10mm/day and the average was determined as4.5 ± 2.7mm/day inthe study area. Inthe calculations made with the empirical models, the change inThornthwaiteAdjis1.3–6.6mm/day with anaverage of3.8 ± 1.6mm/day, the change inBlaney-Criddle is1.8–7.2mm per day with anaverage of5.1 ± 1.4, the change inPM is1.2–10.5mm/day with anaverage of5.8 ± 2.7 mm/day, the change inJensen-Haise was 5.8 ± 2.7mm/day with anaverage of5.5 ± 2.7mm/day, and the change inASCE SZ PM was calculated as1.0–10.1mm/day with anaverage of5.4 ± 2.5mm/day. Considering the obtained results, the ETGaugeequipment can be used safely in creating irrigation programmes.