7 Infiltration and Percolation
The term infiltration represents the entrance of surface water into the ground at the
soil-water or soil-air interface. It is affected by topography, the surface conditions of
the ground, the characteristics of the surface material, and the rate of precipitation. It
is greatest with plowed fields, with vegetative cover, and on flat ground.
Percolation represents the flow of water within the soil in both the horizontal and
vertical directions. There is a fine line of distinction where infiltration ends and
percolation begins. Percolation is controlled by gravity and the type of soil through
which the water is flowing. Percolation will continue in a downward movement until
an impermeable barrier is reached. This may be a very fine material such as clay or
an impermeable substance such as rock. From this point the water will flow in more
of a horizontal direction, but still down slope along the top of the impermeable
barrier. The velocity of flow is a function of the soil material and the amount of water
being applied to force the system in a downward direction as a function of gravity.
This zone of water above the first confining layer is called the free or unconfined
ground water. Since at various locations on the earth there are intermittent layers of
porous and nonporous materials, water may enter a lower level and in flowing
downward may pass under an impermeable layer and become a confined aquifer.
Confined aquifers usually flow under pressure as a function of the connection to the
free ground water surface. Thus there may be numerous aquifers as one proceeds
deeper into the earth. However, as a general rule, the deeper the aquifer, the more
dissolved solids are present and the poorer the quality of the water. Since the free
ground water has the potential to be contaminated from the surface, the most
desirable water from the standpoint of domestic use is usually that found in the
first confining aquifer. A more detailed discussion of ground water is given in a
separate section on ground water.
8 Runoff
Precipitation which does not evapotranspire back into the atmosphere or infiltrate
into the soil as ground water runs across the surface of the earth as runoff, forming
streams and lakes. These may be used as a source of water for various uses including
navigation, recreation, waterpower both directly and in the generation of electricity,
and many industrial uses including production of materials and cooling water.
Surface waters serve as a water supply for many people particularly for large
metropolitan areas. The animals in the water provide food for many people. When
used for irrigation the water may be used for growing crops on land. Runoff
represents the earth’s freshwater resources. Once the water flows to the ocean, it
becomes saline and takes on significantly different characteristics.
6 Basic Hydrology, Water Resources, and DAF Boat Plant for Lake Restoration
251
The term infiltration represents the entrance of surface water into the ground at the
soil-water or soil-air interface. It is affected by topography, the surface conditions of
the ground, the characteristics of the surface material, and the rate of precipitation. It
is greatest with plowed fields, with vegetative cover, and on flat ground.
Percolation represents the flow of water within the soil in both the horizontal and
vertical directions. There is a fine line of distinction where infiltration ends and
percolation begins. Percolation is controlled by gravity and the type of soil through
which the water is flowing. Percolation will continue in a downward movement until
an impermeable barrier is reached. This may be a very fine material such as clay or
an impermeable substance such as rock. From this point the water will flow in more
of a horizontal direction, but still down slope along the top of the impermeable
barrier. The velocity of flow is a function of the soil material and the amount of water
being applied to force the system in a downward direction as a function of gravity.
This zone of water above the first confining layer is called the free or unconfined
ground water. Since at various locations on the earth there are intermittent layers of
porous and nonporous materials, water may enter a lower level and in flowing
downward may pass under an impermeable layer and become a confined aquifer.
Confined aquifers usually flow under pressure as a function of the connection to the
free ground water surface. Thus there may be numerous aquifers as one proceeds
deeper into the earth. However, as a general rule, the deeper the aquifer, the more
dissolved solids are present and the poorer the quality of the water. Since the free
ground water has the potential to be contaminated from the surface, the most
desirable water from the standpoint of domestic use is usually that found in the
first confining aquifer. A more detailed discussion of ground water is given in a
separate section on ground water.
8 Runoff
Precipitation which does not evapotranspire back into the atmosphere or infiltrate
into the soil as ground water runs across the surface of the earth as runoff, forming
streams and lakes. These may be used as a source of water for various uses including
navigation, recreation, waterpower both directly and in the generation of electricity,
and many industrial uses including production of materials and cooling water.
Surface waters serve as a water supply for many people particularly for large
metropolitan areas. The animals in the water provide food for many people. When
used for irrigation the water may be used for growing crops on land. Runoff
represents the earth’s freshwater resources. Once the water flows to the ocean, it
becomes saline and takes on significantly different characteristics.
6 Basic Hydrology, Water Resources, and DAF Boat Plant for Lake Restoration
251