Abstract: Researching the impact of agricultural irrigation on the groundwater dynamic under different crop growth conditions in arid and semi-arid area holds significant practical importance for the rational development and utilization of regional groundwater. Using the MODFLOW-NWT program and unsaturated zone simulation subroutine package UZF1 in GMS software, a numerical model was established for the northern bank of the Kaidu River in the Yanqi Basin. The model was calibrated using daily groundwater level data. Water balance analysis was also conducted. Water requirement for five typical crops (peppers, tomatoes, wheat, sugar beets, and corn) was computed using the crop coefficient method. The calibrated groundwater model was used to simulate the effects of agricultural irrigation on the groundwater depth dynamic under different planting scenarios. The results show that planting the high-water-consumption sugar beets corresponds to the greatest average groundwater depth, while planting wheat results in the smallest average groundwater depth. Average Groundwater depth are similar when planting tomatoes, peppers, and maize. During sugar beets cultivation, the average groundwater depth is 0.85 meters greater than during wheat cultivation. With a 100-millimeter-increase in water demand, the average groundwater depth increases by 0.31 meters during the growing season. It indicates that crop water requirement is a crucial factor affecting groundwater level fluctuation in study area. The finding can provide a scientific guidance for the sustainable management of water resources and the formulation of agricultural planting strategy of arid and semi-arid area. 

Key words: groundwater, numerical simulation, Yanqi Basin, agriculture irrigation, MODFLOW-NWT