Regional dynamics in the irrigation requirement of maize and wheat crops in relation to changes in the climate and cultivated area in the Shandong’s Yellow River Basin

Under the dual pressures of climate change and human activities, the irrigation water requirement (IWR) in the irrigated areas has undergone notable changes, posing major challenges for balancing regional water supply and demand and ensuring food security. In this study, the Theil–Sen estimator and Mann–Kendall analysis were used to elucidate the spatiotemporal variation characteristics of meteorological factors, cultivated area, and IWR based on the long-series data from 2003 to 2023 in the Shandong’s Yellow River Basin. The impacts of meteorological factors and cultivated area on the IWR variations were explored by combining sensitivity analysis and contribution analysis method. Hurst exponent was used to assess the persistence of historical trend. The results revealed that the study area experienced a pronounced “warm-dry” trend, characterized by notable increase in temperature (T), sunshine duration (SD), and potential evapotranspiration (ETo), overall decline in relative humidity (RH) and wind speed (Ws), and cultivated area expanded by 3.3 % per year. These factors collectively led to a rise of 48.23 m3ha−1 per year in IWR and a distinct north–south spatial differentiation. Cultivated area as the dominant driver of IWR, contributing 0.61 × 108 m3, while declining RH and rising T were the primary climatic contributors to increased IWR, with respective contributions of 0.15 × 108 m3 and 0.13 × 108 m3. RH and T were the dominant factors in the southwest, whereas parts of the north exhibited high sensitivity to changes in planting area. Most of the area will continue to follow historical trends, with total volume of IWR is expected to rise from 176.27 × 108 m3 in 2023–216.22 × 108 m3 in 2033, an increase of 22.7 %. This intensifies the contradiction between water supply and demand, highlighting the urgent need to develop differentiated water conservation and climate adaptation strategies.