This document discusses different types of irrigation wells. Lift irrigation involves pumping water from a source to higher elevations for irrigation. Shallow wells are less than 50 feet deep and tap into upper aquifers, while deep wells are over 22 feet deep. There are two main types of wells - water table wells whose levels change with rainfall, and artesian wells where underground pressure forces water up. Open wells can be unlined or lined using precast concrete rings or masonry walls. Tube wells consist of bored pipes that penetrate multiple water-bearing layers between impermeable surfaces, with shallow wells less than 40 meters and deep wells over 200 meters tapping deeper aquifers.

1. LIFT IRRIGATION
Definition
Irrigation is the science of applying water to the soil by artificial means for sustenance of plant growth.
While Lift Irrigation would simply means lifting of water for irrigation, the term Lift Irrigation Scheme (LIS)
in the present context would mean a scheme in which an appreciable quantity of water would be raised
by means for a pump (lifting device) from a dependable source of water to an appropriate height for
irrigation of an area located at a level higher than that of the water source.
In conventional Lift irrigation practice, water is released at an elevated location so that irrigation of the
desired area is performed under gravity flow through open channels or buried pipe lines . In sprinkler and
drip irrigation system however, water is applied by means of a pump directly to the crops.
Both the surface and ground water reservoirs are used as the dependable source or water for
irrigation. While the common surface water sources are rivers, streams, canals and tanks, groundwater
resource through open dug wells, tube wells and dug cum bore wells is also used as a dependable
source under favourable hydrological conditions.
Shallow wells
A hole which has been dug, bored, driven or drilled into the ground for the purpose of extracting water is
a well. A well is considered to be shallow if it is less than 50 feet deep. The source of a well is an aquifer.
An aquifer is an underground layer of permeable soil (such as sand or gravel) that contains water and
allows the passage of water.
Aquifers are replenished as rainfall seeps down through the soil. Ground water travels through
permeable soil on top of hard or impermeable layers. Shallow wells usually are only deep enough to
intercept the uppermost (or most easily reached) perched water table.
There are two main types of wells:
Water table wells are those that penetrate into aquifers in which the water is not confined by an
overlying impermeable layer. The level at which the soil is saturated is the water table. Pumping the well
lowers the water table near it. These wells are particularly sensitive to seasonal changes and may
dwindle during dry periods.
Artesian wells penetrate into ground water having confining layers above and below the aquifer.
Rainfall enters into the aquifer through permeable layers at high elevations causing the ground water to
be under pressure at lower elevations. Because of this pressure, the water level in the well is higher than
the aquifer. A well that yields water by artesian pressure at the ground surface is a "flowing" artesian
well.
Deep wells
A well in which the water level is at a depth exceeding 22 feet beyond which the ordinary suction pump
does not operate satisfactorily. To access the complete Unabridged Dictionary, with an additional
300,000 words that aren't in our free dictionary, start a free trial.
Aquifer wells types
An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials
(gravel, sand, orsilt) from which groundwater can be extracted using a water well. The study of water
flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms
include aquitard, which is a bed of low permeability along an aquifer and aquiclude (or aquifuge), which
is a solid, impermeable area underlying or overlying an aquifer. If the impermeable area overlies the
aquifer, pressure could cause it to become a confined aquifer
Aquifers may occur at various depths. Those closer to the surface are not only more likely to be used for
water supply and irrigation, but are also more likely to be topped up by the local rainfall. Many desert
areas have limestone hills or mountains within them or close to them that can be exploited
as groundwater resources.

2. Ground water flow
Groundwater flow is defined as the "...part of streamflow that has infiltrated the ground, has entered
the phreatic zone, and has been discharged into a stream channel, viasprings or seepage
water". In hydrogeology it is measured by the Groundwater flow equation. Groundwater is water that is
found underground in cracks and spaces in the soil, sand and rocks. The area where water fills these
spaces is called saturated zone. Groundwater is stored in and moves slowly through the layers of soil,
sand and rocks called aquifers. The speed at which groundwater flows depends on the size of the
spaces in the soil or rocks and how well the spaces are connected.
Construction of open wells
Open wells may be unlined or lined
1.Construction of Unlined Wells
This type of open well is constructed in hard soil. In this case, the excavation of earth is started
according to the required diameter of the well.The excavation is continued until the water rushes out
from the bottom. Generally , the diameter varies from 1.5 m to 2m and the depth varies from 10m to 12
m. As lining is not provided in this well , it is very cheap. This type of well is common in hilly areas.
2.Construction of Lined Open Wells
a. By pre-cast R.C.C. Rings – In this case, a pit is first excavated up to a depth of 30cm according to
the diameter of the rings and one ring is placed in position perfectly. Then two more rings are set on it.
Now , excavation is started and the rings go on sinking gradually due to their weight. More and more
rings are set over the previous rings and the excavation proceeds. Finally, the water rushes out from the
bottom . In village area, the earthen ware rings are generally used. The diameter of this type of well
varies from 1 m to 1.5m and depth varies from 15m to 18m . care should be taken for the vertical sinking
of well.
b. By masonry wall- In this case, a pit is first excavated up to a depth of 30cm and a well curb(made of
steel, wood or R.C.C.) having a cutting edge at the bottom is placed in position. The top width of the
circular curb is equal to the thickness of the well wall . On the top of the well curb the masonry wall is
constructed up to a height of 1.5 m . After proper curing of the wall, the excavation is started inside the
well and below the curb. The masonry wall goes on sinking due to its weight. The masonry wall is
constructed step- by – step (1.5 m height at a time ) as the excavation proceeds. Thus the well is sunk
up to the required depth .the verticality of the wall should be maintain with a Plumb bob.
Construction of Tube-wells
A tube well consist of G.I. pipes of diameter varying from 3.75 cm to 15 cm and of length varying from
7m to 8m. The tube well is sunk into the ground by boring. The joints of the pipe are socket joints. It
penetrates a number of water bearing strata which are sandwiched between the impervious layers.
Again, the tube well maybe shallow or deep. The diameter of shallow tube well varies from 3.75 cm to 5
cm and the depth varies from 30 m to 40 m .
The discharge of this well depends on the water table. If the water table goes below the suction head in
summer, the tube well is likely to defunct.
The diameter of deep tube well varies from 10cm to 15 cm and the depth from 200m to 300 m. It draws
water from the deeper most aquifers. Hence , the water is available throughout the year.
Yield of an open tube well