A Richards-equation-based soil moisture module was developed and integrated within the Soil and Water Assessment Tool (SWAT). Four years of daily soil moisture measurements from 10 monitoring stations at three depths (i.e., 5, 10, and 50 cm) in the Choptank River watershed, Maryland, were used to test the module performance. Results show that, as compared with the original SWAT soil moisture module, the Richards-equation-based soil moisture module improved R² from 0.12 to 0.45 and reduced soil moisture simulation bias (mean[simulation] – mean[measurement]) from −0.10 to −0.02 (m³ m⁻³), averaged across the 10 stations at soil surface layer (i.e., 5 cm depth). Noticeable improvements were also observed for deeper soil layers, and for both dry and wet periods. Notably, the soil moisture coupling strength between different soil layers was substantially improved with the new module. The enhanced SWAT model is expected to better inform soil water and irrigation management.

开发了基于Richards方程的土壤湿度模块，并将其集成到土壤和水评估工具（SWAT）中。在马里兰州乔普坦克河流域的三个深度（即5、10和50厘米）的10个监测站​​进行了为期四年的每日土壤湿度测量，以测试模块的性能。结果表明，与原始的SWAT土壤水分模块相比，基于Richards方程的土壤水分模块将R ²从0.12提高到0.45，并将土壤水分模拟偏差（均值[模拟] –均值[测量]）从-0.10降低了。至-0.02（m ³ m ^-3），在土壤表层（即5厘米深）的10个站点上取平均值。在更深的土壤层以及干燥和潮湿时期也观察到了明显的改善。值得注意的是，新模块大大提高了不同土壤层之间的土壤水分耦合强度。增强的SWAT模型有望更好地为土壤水和灌溉管理提供信息。