Artesian aquifers and water pressure

An artesian aquifer is a confined aquifer containing groundwater that is under pressure. The pressure in the aquifer is usually caused by the weight of water in the recharge area, which pushes down on the water in the aquifer. This pressure can cause water to flow upwards to the surface, without the need for a pump.

Water pressure in an artesian aquifer is typically measured in pounds per square inch (psi) or in meters of head. The pressure in the aquifer can be either above or below atmospheric pressure, depending on the depth of the aquifer and the elevation of the recharge area.

Explanation of options

a) At sub atmospheric pressure - This option is incorrect because water in an artesian aquifer is usually under pressure and therefore, cannot be at sub atmospheric pressure.

b) At atmospheric pressure - This option is incorrect because water in an artesian aquifer is usually under pressure and therefore, cannot be at atmospheric pressure.

c) At 0.5 times of the atmospheric pressure - This option is incorrect because the pressure in an artesian aquifer can vary depending on the depth of the aquifer and the elevation of the recharge area. It is not always at a fixed fraction of atmospheric pressure.

d) Above atmospheric pressure - This option is correct because water in an artesian aquifer is usually under pressure and can be above atmospheric pressure.

Conclusion

In conclusion, water present in an artesian aquifer is usually under pressure and can be above atmospheric pressure. This pressure is caused by the weight of water in the recharge area, which pushes down on the water in the aquifer. The pressure in the aquifer can be measured in psi or in meters of head and can vary depending on the depth of the aquifer and the elevation of the recharge area.