Abstract
Variation in soil water content in the delta plain has its own particularity and is significant for agricultural improvement, the utilization of water resources and flood risk mitigation. In this study, experimental data collected from a plot of farmland located in the Taihu Basin were used to investigate the temporal and vertical variation of soil water content, as well as the effects of individual rainfall on soil water and shallow groundwater and their interaction. The results showed that the variation of soil water content is dependent on the comprehensive influence of soil hydraulic properties, meteorological factors and shallow groundwater and the correlation to the groundwater table is the strongest due to the significant capillary action in the delta plain. A saturated-unsaturated three-dimensional soil water numerical model was developed for the study area in response to rainfall and evapotranspiration. Scenario simulations were performed with different soil depths for soil water content and the error source was analyzed to improve the model. The average RMSE, RE and R2 values of the soil water content at the five depths between the measured and simulated results were 0.0192 cm3·cm−3, 2.09% and 0.8119, respectively. The results indicated that the developed model could estimate vertical soil water content and its dynamics over time at the study site at an acceptable level. Moreover, further research and application to other sites in delta plains are necessary to verify and improve the model.
Highlights
Most delta plains are lowlands, which are often densely populated and form centers of agricultural production, economic activity and transportation [1] such as the Taihu Basin in the Yangtze River Delta, East China, approximately 30% of which are lowland polders [2]
The results indicated that the soil water contents in the topsoil at depths between 10 cm and 20 cm were much more affected by meteorological factors than groundwater, while those below depths of 40 cm were related to the shallow groundwater table in the field
Soil water is a determinant part in the interaction between surface water and groundwater, both of which are important for crop growth and for farm planning decisions
Summary
Most delta plains are lowlands, which are often densely populated and form centers of agricultural production, economic activity and transportation [1] such as the Taihu Basin in the Yangtze River Delta, East China, approximately 30% of which are lowland polders [2]. For certain types of applications, a successful synopsis of both monitoring and modeling issues was presented by Morbidelli et al [41] that referred to the experimental field campaigns carried out to measure the soil water content with the TDR method in the vertical soil profiles of five different plots. It was not designed for delta plains with shallow groundwater.
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