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The Geosphere and Geochemistry
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Most groundwater originates as meteoric water from precipitation in the form of rain or snow. If water from this source is not lost by evaporation, by transpiration, or to stream runoff, it may infiltrate into the ground. Initial amounts of water from precipitation onto dry soil are held very tightly as a film on the surfaces and in the micropores of soil particles in a belt of soil moisture. At intermediate levels, the soil particles are covered with films of water, but air is still present in larger voids in the soil. The region in which such water is held is called the unsaturated zone or zone of aeration and the water present in it is vadose water. At lower depths in the presence of adequate amounts of water, all voids are filled to produce a zone of saturation, the upper level of which is the water table. Water present in a zone of saturation is called groundwater. Because of its surface tension, water is drawn somewhat above the water table by capillary-sized passages in soil in a region called the capillary fringe.
Water and the Hydrogeology of Watersheds
Published in Daniel T. Rogers, Urban Watersheds, 2020
As surface water continuous its journey downward through the unsaturated zone it encounters the capillary fringe. The capillary fringe is the subsurface layer where groundwater seeps up from the water table by capillary action to fill pore spaces (USGS 1999). At the base of the capillary fringe the pore spaces are filled with water due to tension saturation. The thickness of the capillary fringe is dependent upon the balance between the soil/sediment’s adhesion binding capability and surface tension, and the gravitational force of the lifted water mass. What factors prevail here? In most cases, the thickness of the capillary fringe is less in course-grained materials than finer-grained materials (Payne et al. 2008). Figure 3.21 shows the vertical arrangement of the subsurface zones just described.
Preferential Flow in Structured and Sandy Soils: Consequences for Modeling and Monitoring
Published in L.G. Wilson, Lorne G. Everett, Stephen J. Cullen, Handbook of Vadose Zone Characterization & Monitoring, 2018
Tammo S. Steenhuis, J.-Yves Parlange, Sunnie A. Aburime
The field experiment carried out on Long Island was to determine if a nematicide, Mocap, could be used to control the nematode population without contaminating the ground water. The field selected was located in the town of Jamesport, NY. The root zone was approximately 75 cm deep and consisted of sandy loam. The intermediate zone consisted of coarse sand with clay lenses at the 180 cm depth, gravel layers below the 2.3 m depth, and the water table at a depth of 2.7 m. The capillary fringe was estimated to be 30 cm in thickness. Porous cup lysimeters were installed at 60, 75, 170, 180, 190, 230, and 260 cm depths. Suction was applied for one day each month. Figure 5.12 shows the concentration of Mocap obtained from those regions yielding samples. The samplers at 75, 170, 190, and 230 cm, which were all located in the intermediate zone, did not collect any water. Only samplers in the root zone and capillary fringe and one sampler at 180 cm (probably above a structural interface) yielded sufficient volume to be analyzed for Mocap. Porous cups in the capillary fringe yielded the samples of greatest volume.
Effect of sediment transport, flow depth and infiltration on soil moisture profiles in irrigation furrows
Published in Journal of Applied Water Engineering and Research, 2023
Kapil Rohilla, Sanjay Kumar, Satish Kumar
Figure 14(b) provides the soil moisture characteristics curve at different values of . As the value of increases, the moisture content reduces due to a reduction in capillary fringe thickness of the soil. It can also be seen from Figure 14(b) that at a lower value of , the soil holds a considerable amount of moisture in the soil at a higher value of pressure head as compared to a greater value of due to enhancement in capillary fringe thickness. For the higher value of , soil loose most of the moisture at a lower value of pressure head due to the reduction in capillary fringe thickness of the soil.