Soil and the Gobal Water Cycle
There is roughly six times more water stored in the global soil resource than is stored in the Earth's atmosphere?
In fact, annually, more than 29,000 trillion gallons of water fall from the atmosphere onto the surface of the Earth, much of it landing on soil. To put that in perspective, if you could build a swimming pool the size of Texas, the sidewalls would have to be more than 1,800 feet tall to contain all of the rain. A siginificant portion (approximately 63%) of the precipitation falling evaporates and returns to the atmosphere. Another thirty five percent of the precipitation is not absorbed by the surface of the soil and is actually what feeds the creeks, streams, rivers and lakes of the planet.
The remaining water is that reaches the Earth's surface seeps into the ground through the process known as infiltration. The rate at which water enters the soil is not constant...its affected by the slope, amount and type of vegetation, the soil or rock type and the amount of water already in the soil. Although less than two percent of precipitation eventually finds its way into the soil, the quantity of water is still quite substantial accounting for an annual cycle of roughly 396 trillion gallons. In rural areas, this influx of water is what recharges the groundwater used for drinking, manufacturing and crop production. As you can imagine, any conservation practice that improves the infiltration of rain or snow-melt can have significant impacts on the sustainability of human life as we know it.