Lake Ice and
Snow Science
BASIC CONCEPTS: Hydrological Cycle Facts
Over 70% of the earth's surface is covered by water. However, not all of it is useable by human beings. Some sources of freshwater have long "replacement" times.
| ALL WATER ON EARTH | |
 |
|
| Oceans% 97.5 | Freshwater% 2.5% |
|
|
| Glaciers and permanent snow 79.0% | |
| Fresh ground water 29.9% | |
| Freshwater lakes and river storage (only renewable portion of the system) 0.3% |
|
| Other sources including soil moisture, swamps and permafrost 0.9% | |
QUESTION: How much of the earth's water supply is accessible for human consumption?
RENEWAL TIME OF SOME FRESHWATER SOURCES
| Water in the Hydrosphere | Period of Renewal |
| Ocean | 2500 years |
| Ground water | 1400 years |
| Polar ice | 9700 years |
| Mountain glaciers | 1600 years |
| Ground water in permafrost zone | 10000 years |
| Lakes | 17 years |
| Bogs | 5 years |
| Soil moisture | 1 years |
| Channel network | 16 days |
| Atmospheric moisture | 8 days |
QUESTION: How long does it take to completely replace the water in the hydrosphere?
Source: All data United Nations Educational, Scientific and Cultural Organization