Chairman: Dr. Rakesh Kumar & Dr. S. Balasubramanyam
order to reach a phreatic aquifer, water from precipitation, from irrigation, or
from an influent river, infiltrates from the ground surface and percolates
downward through the unsaturated zone. The same is true for the pollutants
carried with water. These pollutants might already been present in water
reaching the ground surface, or they may be added to water by the processes of
leaching, dissolution, and desorption along their path, from the ground surface
to the underlying aquifer. Solid waste in landfills, septic tanks, fertilisers,
pesticides and herbicides, applied over extended areas and dissolved in water
applied to the ground surface, may serve as examples of sources of pollutants
that travel through the unsaturated zone. Hence the understanding and
consequently the ability to assess and predict the movement of water in the
unsaturated zone is essential when we wish to determine the (total)
replenishment of a phreatic aquifer as part of our groundwater flow model.
Information on the movement of water is also needed in order to foretell the
movement and accumulation of pollutants in the unsaturated zone and the rate and
concentration at which the pollutants reach the water table.
and drainage engineers are faced with the problem
of getting water into or out of the soil. In either case, the flow
phenomenon involved is flow through partially saturated porous media. When water
enters a soil, air must be replaced; and when water is removed, air must enter.
The flow, therefore, involves two largely immiscible fluids: air and water. In
the design of drainage and irrigation systems, engineers (with rare exception)
have made the simplifying assumptions that soil is either completely saturated
water or it is completely unsaturated and that resistance to flow of air
(associated with the movement of water into and out of soil) is negligible. Such
assumptions are in most cases far from realistic. In real cases, there exist
functional relationships among the saturation, the pressure difference between
air and water, and the permeabilities
of air and water. The present work describes these functional
relationships and the properties of porous media, which affect them. Regardless
of the scales involved, the soil hydraulic properties, which affect the flow
behaviour, are incorporated into two fundamental characteristics:
the soil water retention curve describing the relation between volumetric
soil water content and soil water pressure; and
the relation between volumetric water content and hydraulic conductivity
samples from Thirnahalli, Mallasandra and Makali villages were collected.
Suction pressure (y
m ) of water for corresponding moisture contents (q
in cc/cc) were measured in the laboratory. The soil moisture curves were
developed. A rigorous evaluation of several texture based regression models
proposed in the literature indicated their superiority in predicting the
laboratory SMC rather than the field measured one.
equations for the study site are:
Tirnahalli study area, Chickballapur - y
Mallasandra study area, Tumkur - y
Makali village study area, Bangalore - y
unsaturated hydraulic conductivity models developed for the three study areas
Tirnahalli site – K (q)
= 4.41 x 10-5 [(q
- 0.01)0.5 (e23 – 1)2]
Mallasandra, Tumkur - K (q)
= 1.16 x 10-6 [(q
- 0.01)0.5 (e50 – 1)2]
Makali village - K (q)
= 6.9 x 10-8 [(q
- 0.01)0.5 (e41.54 – 1)2]
one dimensional flow model is developed for predicting vertical flow in the
unsaturated zone of the homogenous soils. The model is developed based on the
pressure head form of Richards equation. This form is chosen to couple the
unsaturated flow model with saturated flow models. The cumulative infiltration
derived from the solution is of the form of Green-Ampt infiltration equation.
The analytical model is capable of incorporating soil properties ranging from
weakly non-linear to those of a highly non-linear Green-Ampt like model. The
analytical solution describes the development of the moisture content profile
during constant infiltration and capable of predicting the time dependence of
both soil moisture content and soil moisture potential.
UGC-DSA Center in Fluid Mechanics,
Department of Mathematics, Bangalore University,
Central College Campus, Bangalore 560 001.
Faculty of Civil Engineering, Jnanabharathi,
Bangalore University, Bangalore 560 056.