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Water is constant.

Water moves continuously below, on, and above the surface of the earth. Individual water molecules may come and go quickly or very slowly, but the overall amount of water remains fairly constant.

Reservoir

Atmosphere

Soil

Seasonal snow cover

Rivers

Glaciers

Lakes

Groundwater, shallow

Groundwater, deep

Polar ice sheets

Average residence

9 days

1 to 2 months

2 to 6 months

2 to 6 months

20 to 100 years

50 to 100 years

100 to 200 years

10,000 years

10,000 to 1,000,000 years

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