Evaluation of Soil Water Availability (SWA) Based on Hydrological Modelling in Arid and Semi-Arid Areas: A Case Study in Handan City, China

To evaluate the spatial and temporal soil water availability (SWA) and improve the soil water use efficiency in agriculture, this study established a new index system for SWA evaluation considering the soil storage capacity, the temporal and spatial matching degree between soil water supply and crop water demand, and the soil water transformation and utilization efficiency. To quantitatively calculate the indexes, a self-developed hydrological model (MODCYCLE) was introduced and applied in Handan City. The results show that MODCYCLE performed well in simulating the soil hydrological processes. A comparison of the observed soil moisture data and the simulated values revealed relative errors below 10% and correlation coefficients all above 0.7. According to the evaluation results, the SWA for different typical years was very unevenly distributed in Handan City. The average SWA in a normal year is 0.71, which is higher than that in dry years at 0.62 and in wet years at 0.65. Regarding different regions, the average SWA was generally much higher in the eastern plain area than that in the western mountainous area. Generally, there is a great potential for improving SWA and further the sustainable development of soil water resource, particularly for dryland farming in similar areas.