Infiltration and drainage processes of different textural soil moisture in middle reaches of Heihe River Basin

Abstract: Heihe River irrigation region is typical arid agricultural oasis. It is also important commodity grain, cotton and oil-producing areas. Water shortage is a key issue of limiting socio-economic development. Flood irrigation is still the main irrigation methods about agricultural production and they believe that a large number of farmland irrigation result in high crop yields. This approach not only reduces water use efficiency but also wastes a lot of valuable water resources. Therefore, investigating soil moisture movement laws has important theoretical significance and practical value for the agricultural water-saving irrigation. Although many related results for infiltration and drainage of soil moisture have been reported in previous literature, most of the studies have been focused on the Loess Plateau, red soil area of South China and karst area of Southwest China, few on arid oasis area. The double-ring infiltrometer is used to measure infiltration by the constant-head method, composed of inner-ring and outer-ring whose diameters are 80cm and 100cm, respectively. Representative position in the maize farmland and protection forestland was chose, and the Trime Tube depth of 275 cm and 265 cm was installed, respectively. The double-ring was embedded in soil and the water depth of the inner and outer-ring was 5 cm. Soil water content of infiltration and drainage processes was measured by Trime-IPH TDR and soil water movement was simulated accurately by Hydrus-1D model. Results of the simulations indicated that the soil textures significantly affected water infiltration and drainage. The finer grained layer was capillary barriers for water infiltration and drainage as well as had strong water holding capacity. The statistical analysis indicated that root mean square error (RMSE) and the relative error (RE) between the measured and estimated soil water content were below 0.02 and 0.68%, respectively. Root mean square error (RMSE) and the relative error (RE) between the measured and estimated soil water storage were below 0.908 and 0.9% respectively. HYDRUS-1D model had a high precision for the simulation of water transport of the oasis soil in vertical direction. The results can provide a scientific basis for water management and sustainable development of Heihe River Basin.