Effects of shallow groundwater table on soil matric potential and hydraulic characteristics

Abstract

Groundwater recharge significantly affects soil moisture redistribution through capillary rise. In this study, the soil matric potential at depths of 5, 10, 20 and 30 cm above the groundwater tables of 10, 30 and 60 cm were measured for 5 d. Soil hydraulic properties were analyzed by using the Philips and de Vries model. Results showed that evaporation mainly influenced the matric potential of the shallow layer at the 5 cm depth regardless of the saturation of the layer. Groundwater recharge mainly affected soil moisture at the depth of 20 cm or more. A constant matric potential layer existed between the evaporation front and capillary rise front where moisture content did not change. The isothermal-liquid hydraulic conductivity (K _Lh) and the thermal-vapor hydraulic conductivity (K _vT) were the dominant hydraulic conductivities in the liquid and vapor phases. At the groundwater table depths of 10, 30 and 60 cm, the mean peak values of K _Lh were 2.32×10⁻⁷, 1.63×10⁻⁷ and 0.29×10⁻⁷ m/s, respectively, whereas the mean peak values of K _vT were 2.7×10⁻⁷, 2.4×10⁻⁷ and 1.8 ×10⁻⁷m/s, respectively.

Keywords

shallow groundwater / matric potential / thermal hydraulic conductivity / isothermal hydraulic conductivity

References

[1] Philip J R, De Vries V D. Moisture movement in porous materials under temperature gradient [J]. Transactions-American Geophysical Union, 1957, 38(2): 222-232.

[2] Zeng Y, Wan L, Su Z, et al. Diurnal soil water dynamics in the shallow vadose zone (field site of China University of Geosciences, China) [J]. Environmental Geology, 2009, 58(1): 11-23.

[3] Fan Z, Neffa Jason C, Jennifer W H, et al. Water and heat transport in boreal soils: Implications for soil response to climate change [J]. Science of the Total Environment, 2011, 409(10): 1836-1842.

[4] Saito H, Šimunek Jiri. Effects of meteorological models on the solution of the surface energy balance and soil temperature variations in bare soils [J]. Journal of Hydrology, 2009, 373(3/4): 545-561.

[5] Zeng Y, Su Z, Wan L, et al. Diurnal pattern of the drying front in desert and its application for determining the effective infiltration [J]. Hydrology and Earth System Sciences, 2009, 6(1): 1021-1054.

[6] Scherm H, Yang X B. Development of sudden death syndrome of soybean in relation to soil temperature and soil water matric potential [J]. Phytopathology, 1996, 86(6): 642-649.

[7] Denis C, Beare H M, Hernandez-Ramirez G. Temperature and moisture effects on microbial biomass and soil organic matter mineralization [J]. Soil Science Society of America Journal, 2012, 76(6): 2055-2067.

[8] Marcel G S, Feike J L. Improved prediction of unsaturated hydraulic conductivity with the Mualem — van Genuchten model [J]. Soil Science Society of America Journal, 2000, 64(3): 843-851.

[9] Dexter A R. Soil physical quality Part III: Unsaturated hydraulic conductivity and general conclusions about Stheory [J]. Geoderma, 2004, 120(3/4): 227-239.

[10] Sakaguchi A, Nishimura T, Kato M. The effect of entrapped air on the quasi-saturated soil hydraulic conductivity and comparison with the unsaturated hydraulic conductivity [J]. Vadose Zone Journal, 2005, 4(1): 139-144.

[11] Gran M, Carrera J, Massana J, et al. Dynamics of water vapor flux and water separation processes during evaporation from a salty dry soil [J]. Journal of Hydrology, 2011, 396(3/4): 215-220.

[12] van Genuchten M T, Leij F J, Yates S R. The RETC Code for Quantifying the Hydraulic Function of Unsaturated Soils [M]. 1991, Washington, USA: United States Environmental Protection Agency.

[13] Wang J, Yang Z, Chen J, et al. Study on water hysteresis in aerated soil [J]. Journal of Hydraulic Engineering, 2000, 2(2): 1-6.

[14] Yang Y, Wang Doutian. Determination of soil permeability and the soil improvement in shore saline region [J]. Tianjin Agricultural Sciences, 1999, 5(3): 29-31.

[15] van Genuchten M Th. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils [J]. Soil Science Society of America Journal, 1980, 44(5): 892-898.

[16] Mualem Y. A new model for predicting the hydraulic conductivity of unsaturated porous media [J]. Water Resources Research, 1976, 12(3): 513-521.