18 Journal of Cereal Research Volume 14 (Spl - 2): 18-26 Research Article Homepage: http://epubs.icar.org.in/ejournal/index.php/JWR Article history: Received: 18 July, 2022 Revised: 04 Aug., 2022 Accepted: 08 Aug., 2022 Citation: Suprava Nath, N Devakumar, SS Patra and A Nanda. 2022. Estimation of crop water requirement and irrigation scheduling of rice in Shivamogga district of Karnatakausing FAO CROPWAT. Journal of Cereal Research 14 (Spl-2): 18-26. http://doi.org/10.25174/2582- 2675/2022/125782 *Corresponding author: E-mail: supravanath96@gmail.com © Society for Advancement of Wheat and Barley Research Estimation of crop water requirement and irrigation scheduling of rice in Shivamogga district of Karnataka using FAO CROPWAT Suprava Nath 1 *, N Devakumar 2 , Sitanshu Sekhar Patra 3 and Abhishek Nanda 4 1,2 Department of Agronomy, University of Agricultural Sciences, Bangalore, Karnataka, India, 560065 3 Department of Meteorology and Oceanography, Andhra University, Visakhapatnam, Andhra Pradesh, India, 530003 4 Department of Agronomy, GBPUA&T, Pantnagar, Uttarakhand, India, 263145 Abstract Climate change is expected to have a signifcant impact on the water needs of rice crop worldwide in the upcoming decades. Proper water management is essential to enhance the crop yield as well as maximising the region’s water use effciency. The objective of this study was to estimate the crop water requirement (CWR) and irrigation scheduling of rice in Shivamogga district of Karnataka using CROPWAT model for a time span of 20 years (2001 to 2020). It was estimated that the crop water requirement of rice was 565.50 mm with the highest and lowest CWR 606.1 and 527.9 mm in 2011 and 2001, respectively. Crop water requirement value showed a slight increasing trend (R 2 = 0.0544) throughout the years from 2001 to 2020. Total gross irrigation (TGI) and total net irrigation (TNI) for rice was 491.61 and 344.12 mm, respectively during the study period. The present study is useful for effective planning and management of irrigation water needs of rice in Shivamogga district of Karnataka. Keywords: Climate change, Crop water requirement, CROPWAT model, Gross irrigation, Irrigation scheduling, Rice 1. Introduction Despite having 18% of the world’s population, India only has 4% of the world’s water resources (Dhawan, 2017). Out of total available freshwater in India, 78 per cent of water is consumed by the agricultural sector (Sharma et al., 2018; Biswas et al., 2022). It is widely acknowledged that the world is experiencing an unprecedented water shortage, and that one of the main factors escalating the situation is poor water management in agriculture (Madani et al., 2016). Climate change has shifted India’s climate to extremes (Mall et al., 2006), changing rainfall patterns and intensity (Wassmann et al., 2009), which has a signifcant impact on crop production, primarily in rainfed areas (Kumar, 2022). Two basic factors are critical- frstly, agriculture is by far the largest user of freshwater and secondly, water use in agriculture tends to have lower net returns as compared to other competing users of fresh water (Moe and Rheingans, 2006; Taheripour et al., 2015). As per estimates, in the future, the world’s food systems will need 40–50% more freshwater than they do now to produce the same amount of food (Foley, 2011). Municipal, domestic as well as industrial demand for fresh water will increase by 50-70 per cent during this period. India has one of the world’s most vulnerable and unreliable water supplies and experiences considerable water stress (Srinivasan et al., 2013). One of the main approaches to these emerging challenges is to focus on improving water productivity in agriculture, as even small improvements could have large implications for local and national water budgets and allocation policies (Hamdy et al., 2003).Managing irrigation water starting from the source to its application to the crop holds a crucial place in improving water use