You might have observed that well water or water pulled out from deep underground using water pumps is felt cold in summer while hot in winter season and you might be wondering why this happens! The reason for this phenomenon is very simple.
Actually, temperature of underground water remains almost constant through out the year because water table is far below from the surface of Earth. Sun is not able to heat such deep underground water. The temperature of underground water could be 10-20 degree Celsius (50-68 °F). It is different for different geographical regions. So, if temperature outside is suppose 40 degree Celsius (104 °F) but underground water is only 15 °C (59 °F), you will feel it cold. In winter, if temperature on surface of Earth is 0 or below 0 °C (32 °F), well water with over 15 degree Celsius (59 °F) temperature will definitely be felt as warm.
The same phenomenon also happens in case of tube well water and the reason remains the same. Tube well which is used for irrigation purposes and to supply water to towns is a type of well having a narrow pipe going down the Earth to underground aquifer. Water is then pulled up using water pumps.
It has been observed that water from deeper well is cooler than the well which is just few feet deep. We have also observed a noticeable temperature difference between well water at cooler regions and in hot deserts. Surrounding temperature has great impact on wells especially open wells.
Note that the regions with little to no rainfall have got water table at extreme depth and water is also salty and unfit for drinking. Places where there are rivers or large streams flowing have got sweet underground water due to the constant percolation of fresh water from top.
Below is the illustration of few water wells. To get water from underground you need to keep digging till some better quality water is obtained.
|Types of water wells. Levels and depth of underground water.
Sometimes, the underground water which is pumped out is very hot. It is a rare case but naturally possible. It happens when underground water comes in contact with burning hot rocks or magma. Hot water falls, geysers and hot natural fountains are also formed due to the result of same contact between water and magma or hot rocks.