Construction of Open wells & Types of Tube wells
It is the part of subsurface water which occur within the saturated zone of earth's crust, where all openings are filled with water. It is that part of the subsurface water which can be lifted or which flows naturally to the earth surface.
Occurence of ground water depends upon two factors:
Transmissibility: it represents the same physical meanings of permeability.
Water table: it can be said as the upper limit of saturated zone.
A saturated geological formation capable of yielding water economically insufficient quantity is known as aquifer or water bearing strata or G. W reservoir.
The ground water is under pressure and water level in the well indicates the piezometric pressure at that point.
Availibility, movement and quality of ground water depends upon characteristics of soil:
It is the ratio of volume of water drained by gravity to its own volume
It indicates the yielding capacity of unconfined aquifer.
It is the amount of water (volume) retained against the force of gravity to its own volume.
Coefficient of permeability:
K of a medium is measured in terms of hydraulic conductivity which is equal to the volume of water which flows in unit time through unit cross sectional area of medium under unit hydraulic gradient at the prevailing temperature units m/d or m/hr
b = aquifer thickness
T = Kb
T is the amount of water which flows through unit width of saturated aquifer under unit h.g
Q = KIA or V = KI
i = H G
A water well is a hole usually vertical excavated in the earth for bringing Gw to surface
Types of tube wells
Design of strainer or well screen
In design, find its length, slot size, opening area, diameter and material requirements