Experimental and numerical investigations of deep soil water infiltration in the Mu Us Sandy Land

Quantification of water flux of sand dunes is an issue in accounting for regional water balance in the Mu Us Sandy Land. The TE525MM-type rain sensor and ECH₂O-5 soil moisture sensor to quantitative monitor precipitation, soil water for 0-200 cm deep in the dune of the Mu Us Sandy Land. The hydraulic properties of the soils at the site were determined using laboratory measurements. A HYDRUS-1D model was built up for simulating the coupling processes of vertical water-vapor movement and heat transport in the desert soil. The soils hydraulic properties using in the model was well calibrated and validated using the site measurements of the soil water and temperature at various depths. Then, the parameters of above calibrated and validated model were applied in the model to simulate the vertical flow across a 2-m-depth soil. The analysis of soil moisture variations, infiltration of rainfall and soil water recharges characteristics showed, most of the soil accumulate water will leak into 200 cm and then recharge deep soil water, with the time increasing. The simulation results showed that the proper deep infiltration depth could be estimated as a certain value for hydrological years with 75%, 50% and 25% probability of rainfall occurrence, respectively. The results may provide a scientific support for ecological construction in the Mu Us Sandy Land in northern China.