Abstract
Estimation of evapotranspiration is necessary for efficient water management and crop planning. Fifteen different methods of ET0 estimation were employed to compute daily reference evapotranspiration for the period 2010 to 2014. In the absence of reliable open pan evaporimeter data, FAO-56 Penman Monteith method was considered as one of the reliable method of ET0 estimation. The results showed that mean weekly evapotranspiration values obtained from Penman-Monteith method were very closer to FAO-56 Penman-Monteith method and values from all the other methods except FAO- 24 Pan, Christiansen Pan and Hargreaves methods generally predicted higher values of mean weekly daily ET0 in comparison to FAO-56 Penman-Monteith method. The analysis shows that mean weekly daily ET0 estimates of combination methods resulted better ET0 estimates than radiation, and temperature and evaporation methods. Weekly ET0 values estimated by FAO-56 Penman-Monteith method were found to vary in the range of 1.3 mm/day to 6.7 mm/day. Average annual reference evapotranspiration was found as 1517.1 mm.
Highlights
Crop water requirement mainly depends upon crop sowing date, crop growth stages, crop duration and climatic conditions during the growing season of an individual crop
Irmark et al in north-central Florida, compared ET0 values obtained from two equations derived from FAO56-PM (first equation was solar radiation (Rs) based and second net radiation (Rn) based) against FAO56-Penman-Monteith method and results were found correlated very well with the standard
Annual reference evapotranspiration in these years were computed as 1535.4 mm, 1523.5 mm, 1485.2 mm, 1501.6 and 1539.9 mm, respectively, and average annual reference evapotranspiration was found as 1517.1 mm
Summary
Crop water requirement mainly depends upon crop sowing date, crop growth stages, crop duration and climatic conditions during the growing season of an individual crop. George et al used DSS model for estimation of reference evapotranspiration for three climatic conditions: Davis, Jagdalpur, and Kharagpur by different applicable methods [2]. Comparison of the estimates of different methods with the Penman- Monteith ET0 estimates showed that Hargreaves, FAO24 Blaney Criddle and 1982 Kimberley- Penman methods ranked first, respectively for the Davis, Jagdalpur and Kharagpur stations. They recommended that DSS model is a user- friendly tool for estimating ET0 under different data availability and climatic conditions. Irmark et al in north-central Florida, compared ET0 values obtained from two equations derived from FAO56-PM (first equation was solar radiation (Rs) based and second net radiation (Rn) based) against FAO56-Penman-Monteith method and results were found correlated very well with the standard
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