<p>Irrigation as a key component of sustainable agriculture, is crucial for ensuring food security. This study examines the effects of climate change on water resources and irrigation demands within the rice-wheat rotation system in the middle and lower Yangtze River basin. Meteorological data from 121 stations (1970–2020) were analyzed using Mann-Kendall tests and climate tendency rates. The FAO-56 Penman-Monteith model, crop coefficients, and effective precipitation quantified crop evapotranspiration and irrigation needs. Drought risks were assessed using the Crop Water Surplus Deficit Index (CWSDI). The results showed that over the past 50 years, temperatures in the middle and lower reaches of Yangtze River had generally increased, with a strong linear warming trend during the rice growing season and more pronounced warming during the wheat growing season, particularly in northern regions. Precipitation patterns also changed over time, in the southern regions, increased rainfall helped alleviate irrigation demands during the rice season. However, in the north, limited rainfall increases led to prolonged water shortages during the wheat season, with significant interannual variability causing fluctuations in irrigation needs. CWSDI analysis revealed that drought risk during the rice season remained relatively stable, typically at a mild level. In contrast, drought severity during the wheat season exhibited an upward trend, with increasing frequency and intensity observed in the northern parts of the study region. Overall, climate change has intensified spatiotemporal disparities in water availability, with increasing drought risk during the wheat season in northern areas, such results underscore the need for targeted, region-specific water management strategies.</p>