Modeling the Impact of Climate Change on Evapotranspiration and Irrigation Requirements of Rice in Chandauli Using NEX-GDDP and CROPWAT

Abstract

A study was conducted to evaluate the impact of climate change on the water requirements of rice crops in the Chandauli district of Uttar Pradesh, where rice is a principal cereal crop. Climate change poses serious threats to food security and water resources, necessitating such assessments. The research employed the CROPWAT 8.0 model to estimate evapotranspiration (ET) and irrigation water requirements (IWR) for rice cultivation. Climate data, including maximum temperature (Tmax), minimum temperature (Tmin), and rainfall, were derived from the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) for both the baseline period (1981–2015) and the future period (2020–2040), under the RCP 4.5 scenario. Due to inherent biases in General Circulation Models (GCMs), two bias correction methods—linear scaling and modified difference—were tested, with linear scaling proving more effective. Climate projections indicate an approximate increase of 1.7 °C in both Tmax and Tmin by 2040. Although total rainfall may rise, effective rainfall (ER) is projected to fluctuate. The study predicts an 8.8% increase in crop water requirements (CWR) by 2040 due to rising temperatures. Meanwhile, irrigation water requirements (IWR) are expected to vary: increasing by 19% in 2020, decreasing by 9% in 2030, and rising again by 2.9% in 2040. These findings underscore the importance of adaptive water management and agricultural planning to mitigate climate change impacts on rice production in the region.