Chapter 9, Problem 1LC

To determine

To explain: Whether the amount of precipitation and evapotranspiration over the continents the same or not.

Answer to Problem 1LC

The amount of precipitation and evapotranspiration are not the same over the continents, rather the precipitation amount goes beyond the amount of evapotranspiration.

Explanation of Solution

Of the total precipitation falling on the Earth, only $22\text{percent}$ reaches the continents while the rest $78\text{percent}$ reaches the oceans. The precipitation falling on the continents undergoes complex series of processes. The water may runoff to the lakes, streams or rivers, infiltrate into the ground and rest goes to the atmosphere through evaporation and transpiration.

The water infiltrated may else be stored as soil moisture or penetrates to even more depth to become a part of the groundwater. The groundwater would appear again on the surface as springs and the soil moisture would ultimately transpire or evaporate into the atmosphere.

If taken on a global scale including both the oceans and land surface the rate of precipitation and evapotranspiration is in balance. But if the continents alone are considered, precipitation surpasses evapotranspiration and vice versa in the case of oceans. The advectional movement of moist marine air onto the land surfaces creates this imbalance between the precipitation and evapotranspiration on continents.