Biochar is widely recognized as an effective soil amendment with strong water-retention capacity. However, the effects of biochars produced at different pyrolysis temperatures on soil water movement remain unclear, and long-term, quantitative assessments are constrained by time and cost. To address this knowledge gap, a two-year field experiment (2023-2024) was conducted in the northern foothills of the Yinshan Mountains, China, to evaluate the effects of biochar pyrolysis temperature (T1: 300 degrees C, low temperature; T2: 500 degrees C, medium temperature; T3: 700 degrees C, high temperature) and application rate (C1: 10 t ha(-1), low rate; C2: 20 t ha(-1), medium rate; C3: 30 t ha(-1), high rate) on soil water distribution and potato productivity. The HYDRUS-2D model was used to simulate soil water dynamics and water balance under different biochar pyrolysis temperatures and application rates in an arid climate. Subsequently, the AquaCrop model was applied to simulate potato yield under various biochar and irrigation scenarios. A multi-objective optimization was performed to identify optimal biochar-irrigation combinations for the potato growing season in North China, targeting yield stability and maximum irrigation water productivity. The results from HYDRUS-2D simulations indicate that the C2T2 treatment has the best moisture regulation capacity. Compared to the CK treatment, soil water retention and root water uptake increased by 30.8% and 48%, respectively, while soil evaporation and soil leakage decreased by 40.9% and 75.9%. AquaCrop simulations show that under normal rainfall conditions, with an irrigation quota of 162 mm, the application of 500 degrees C biochar (20 t ha(-1)) results in higher irrigation water productivity (28.6 kg m(-3)) and potato yield (46.41 t ha(-1)). In extreme rainfall years, the combination of 500 degrees C biochar (20 t ha(-1)) and 102 mm of irrigation is the optimal management strategy for achieving high potato yield while conserving water. These findings provide a theoretical basis for the optimized management of biochar and drip irrigation in potato fields in the Yinshan foothills and similar semi-arid sandy loam regions, and may inform sustainable agricultural practices in comparable environments.