Sustainable water resource management under changing climate in north interior Karnataka: Insights from CROPWAT modelling on soybean

The increasing scarcity of water resources, exacerbated by both natural factors such as increasing erraticity of rainfall over space and time, and human-induced mismanagement practices, poses a significant global challenge. This study focuses on the North Interior Karnataka (NIK) region, characterized by a semi-arid ecosystem, where water resources are under pressure due to a growing demand for food and changing climates. Soybean is an important oilseed crop in NIK and it faces challenges related to climatic variability, thus requires quantifying crop water demand and its management in coming years. CROPWAT model was used to estimate soybean crop water requirement in response to changing climates. Weather data was analysed, including rainfall and temperature, from recent past three decades (1991-2020) and projected climates of coming three decades (2021-2050) across 12 districts of NIK. The model simulated outputs revealed an increasing trend in reference evapotranspiration under projected climates, driven by rising temperatures. Spatial distribution maps across NIK illustrated impact on crop evapotranspiration (ETc) and irrigation requirements (IR), with variations among districts. Further, this study examined the effects of delayed sowing on ETc, revealing a decreased pattern over 60 years. Effective rainfall also influenced irrigation requirements, showing an increase in most districts under projected climates. This work underscored the urgency of efficient use of water. The CROPWAT model proved effective in estimating soybean water requirements, providing valuable insights for sustainable agricultural practices in the face of changing climates and water challenges.