Estimation of Reference Evapotranspiration, Effective Rainfall and Crop Evapotranspiration Using CROPWAT 8.0 in Puttur, Andhra Pradesh, India
C. Aparna *
Vikas College of Engineering & Technology, Nunna, India.
G. Sindhuja
College of Agricultural Engineering, Sangareddy, PJTSAU, India.
Preeti Sajjan
Department of Civil Engineering, Indian Institute of Technology, Bombay, India.
Mallela Prem Kumar
Division of Agricultural Engineering, ICAR-Indian Agricultural Research Institute, New Delhi, India.
*Author to whom correspondence should be addressed.
Abstract
Efficient management of irrigation water requires reliable estimation of evapotranspiration and effective rainfall. The present study evaluated reference evapotranspiration (ETo), effective rainfall and crop evapotranspiration (ETc) for Puttur, Andhra Pradesh, India, using the CROPWAT 8.0 model. Meteorological data including maximum and minimum temperature, relative humidity, wind speed, sunshine duration and rainfall for the period 2019–2023 were obtained from the Regional Agricultural Research Station (RARS), Tirupati. Reference evapotranspiration was estimated using the FAO Penman–Monteith method implemented in CROPWAT 8.0. Effective rainfall was estimated from monthly rainfall data, while crop evapotranspiration was calculated using the crop coefficient approach (ETc = Kc × ETo) for paddy, sugarcane, groundnut and tomato. The results showed a distinct seasonal pattern in reference evapotranspiration, with relatively high values during the warmer months and lower values during the later part of the year. The maximum monthly ETo values were 252.03 mm in May 2019, 252.96 mm in May 2020, 249.55 mm in June 2021, 242.42 mm in May 2022 and 234.36 mm in May 2023. The minimum ETo values were 146.10 mm in November 2019, 142.80 mm in November 2020, 140.70 mm in November 2021, 140.43 mm in January 2022 and 139.19 mm in December 2023. Effective rainfall was highest during October in all five years, with values of 132.2, 133.1, 133.6, 134.1 and 134.5 mm for 2019–2023, respectively. Among the crops evaluated, paddy exhibited the highest crop evapotranspiration, reaching 290.67, 291.74, 287.81, 279.59 and 279.29 mm month⁻¹ during the respective study years. The results demonstrate the usefulness of CROPWAT 8.0 for assessing seasonal crop water demand and effective rainfall and provide information that can support irrigation planning and water-resource management in the study area.
Keywords: CROPWAT 8.0, reference evapotranspiration, effective rainfall, crop evapotranspiration, Penman–Monteith, irrigation water management, Puttur