Simultaneous measurement of water flux density vectors and thermal properties under drainage conditions in soils

Abstract

River water and groundwater are used to irrigate paddy fields and are also principal sources of drinking water for humans. It is important to understand the transport characteristics of water (e.g., direction and intensity of water flow), when grasping a pollution situation in the soil. Endo and Hara (Soc Inst Contr Eng Trans Ind App 2:88–95, 2003) developed the Quintuple-Probe Heat-Pulse (QPHP) sensor to identify water flux density vectors and thermal properties under saturated and steady state conditions. However, there has not yet been any investigation of moisture transfer under transient conditions such as during internal drainage and mid-summer drainage of paddy fields. Only Sand has been used in previous experiments, and examinations with Loamy and Clayey soils have not yet led to done. Simultaneous measurements of the water flux density vectors and thermal properties of soil texture of three types under drainage conditions as well as the soil moisture transfer analysis with Finite Element Method (FEM), were done. The representative drainage flow was indicated as downward, except in the Sandy-Clayey Loam, in which the rightward flux exceeded the downward flux owing to anisotropy of the soil-pore structure and hydraulic conductivity. The apparent horizontal/vertical advanced distance was introduced in order to know about how water moved through the soil column. The estimated volumetric water content was in good agreement with the measured value. Thus, this measurement method was shown to be valid under transient water flow conditions.