Why is groundwater warm in winter and cool in summer?

Winter underground warm water cool summer, why is that? Can groundwater automatically adjust its temperature? Groundwater is water that is several dozen meters below or below the surface of the earth. Its temperature is not much different from that of lava and soils deep underground. Because a thick layer of soil surrounds the groundwater, it can not directly absorb heat from the atmosphere on the ground; it is also difficult to disperse heat into the atmosphere. The heat transfer of the soil deep below again very slowly. So the groundwater stays almost constant and can’t automatically adjust to it.

When groundwater is pumped up to the ground, due to the huge changes in the ground temperature and the four seasons of the year, people experience a different heat and cold from the groundwater. In winter, the air temperature is lower than the groundwater temperature, so people feel that the groundwater is a little warmer; summer air temperature higher than groundwater temperature, people immediately feel groundwater a little cooler.

Suppose a thermometer is used to measure the groundwater temperature in the hot ground (for example, well water). It will be noticed that the summer groundwater temperature is also higher than in the winter. Only the temperature change is generally only 3 – 4 ° C, not as big as the temperature difference on the ground.