Control of Water and Solute Movement in Soil using Geo-Textile

Research Project

Project/Area Number	06660301
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	Irrigation, drainage and rural engineering/Rural planning
Research Institution	Mie University
Principal Investigator	KIYOSAWA Hideki Mie Univ.Fac.Bioresources, Asso.Prof., 生物資源学部, 助教授 (50093125)
Project Period (FY)	1994 – 1995
Project Status	Completed (Fiscal Year 1995)
Budget Amount *help	¥2,200,000 (Direct Cost: ¥2,200,000) Fiscal Year 1995: ¥300,000 (Direct Cost: ¥300,000) Fiscal Year 1994: ¥1,900,000 (Direct Cost: ¥1,900,000)
Keywords	Geo-textile / Soil water movement / Solute transport / Solute accumulation / Farm irrigation / 不飽和透水係数 / 数値シミュレーション
Research Abstract	A buried geo-textile was used to investigate the potential to control the upward migration of solutes under cvaporation from a shallow water table. First, experiments about water and solute distribution measuremants during evaporation using soil columns were conducted. From the data, soil water flux and solute flux through the geo-textile were calculated. The unsaturated conductivity of geo-textile decreased rapidly to about 1/1000 as that of the soil when the surrounding soil suction increasd to only 20cm. Also, the solute flux was proportionate to water flux and was controlled by convection. So, liquid water movement was concluded to be important in controlling solute tansfer to the soil surface. Next, using the characteristics of the soil and the geo-textile obtained in the column experiments, numerical simulation was carried out. Under field conditions of cvaporation from a shallow water table, soil water flux was usually approximated by the product of two functions of time and depth. When geo-textile was buried, the ground water condition makedly afffected the patters of water flux distribution. Deriving the proper distribution functions, an approximate solution was obtained. Using this approximate solution and the numerical simulation, the depth, the thickness, and the characteristics of geo-textile buried considerably affected the soil water flux and solute tranfer.