Comparison of methods for computing soil hydraulic conductivity measured by disc infiltrometer
Gao Xuemei1,2, She Dongli1,2, Fang Kai3
1.Key Laboratory of Efficient Irrigation-Drainage and Agricultural Soil-Water Environment in Southern China, Ministry of Education, Hohai University, Nanjing, Jiangsu 210098, China; 2.National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Hohai University, Nanjing, Jiangsu 210098, China; 3.Suqian Water Conservancy Bureau, Suqian, Jiangsu 223800, China
Abstract：Soil hydraulic conductivity is one of the most important soil hydraulic parameters. Precisely measuring and computing the conductivity not only can promote the theoretical study on water flow process in an unsaturated soil but also can provide a scientific basis for reasonable determination of technical parameters in irrigation and drainage of farmland. To check the applicability of various methods for computing hydraulic conductivity, a series of infiltration experiments are conducted on the soils collected from vegetable and tea gardens by using a disc infiltrometer with 10 cm and 20 cm discs under four different negative pressure heads, namely -9, -6, -3, and 0 cm. Then the conductivities are figured out by means of different computing methods. The results show that the hydraulic conductivity is less affected by the disc diameter, the conductivities given by various methods are nearly the same, and a smaller disc is therefore recommended for the field test. It is suggested that the choice of computing method for the conductivity depends on type of soil, for example, the conductivity of the soil from cultivated land such as a vegetable garden should be estimated by making use of a steady flow model, while for the soil in a tea garden, the transient flow model should be adopted. At the same pressure head, the hydraulic conductivity is obviously dependent on type of soil. The variations of hydraulic conductivity calculated by using different methods are almost the same under four pressure heads for two kinds of soil.
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