Estimation of reference crop evapotranspiration of barley using cropwat model in Punjab

Abstract

Reference crop evapotranspiration (ETo) of barley during Rabi 2016–17 for Gurdaspur and Ludhiana regions of Punjab was computed by CROPWAT model. Seasonal mean reference crop evapotranspiration was relatively higher for Ludhiana (2.74 mm day−1) as compared to Gurdaspur (2.17 mm day−1) region. Higher temperature, wind speed, sunshine hours and lower relative humidity at Ludhiana seemed to be the reason for higher ET rates at Ludhiana than Gurdaspur. Radiation use efficiency was also more for Ludhiana (14 MJ m−² day−1) than Gurdaspur (12.9 MJ m−² day−1), which has also been observed to be directly proportional to the ETo at both the locations. An increase in the temperature by 0.5, 1.0, 1.5 and 2.0°C from the existing temperature was found to increase the ET o by 0.72, 1.82, 2.91 and 4.01%, respectively and water requirement by 1.27, 3.10, 4.26 and 5.56% in the similar order at Ludhiana. The corresponding simulated departures for Gurdaspur were 0.92, 1.38, 2.30 and 3.33% for ET o and 2.65, 3.93, 5.43 and 7.10% for irrigation water requirement. The study concluded that global warming scenarios are likely to increase crop water requirements thus putting tremendous pressure on already over-exploited water resources, suggesting thereby the need for effective planning of water resources in the region.