Hydrosphere• Only planet with

correct atmospheric

pressure and

temperature

to allow water to

exist in all its phases• 97% water held in ocean basins• 2% water frozen• Only 1 % water fresh*

Figure 2-11 (Merritts et al., 1998)

Image ID: corp1893, NOAA Corps CollectionLocation: Alaska SoutheastPhoto Date: August 1991Photographer: Commander John Bortniak, NOAA Corps

The Hydrologic Cycle• Water continuously circulates from the ocean to the atmosphere to the land and

back to the ocean.

• Regardless of its physical form-solid,liquid, or vapor-every molecule of water eventually moves through the hydrologic cycle.

Water sources for Earth included 1) water from icy comets, 2) volcanoes, and 3) minerals.

(Press and Siever, 1986)

Hydrosphere residence times

• Oceans = 3,100 years

• Atmosphere = 9 days

• Continents = 403 years

• Rivers 12 - 20 days

• These residence times are significant for evaluating environmental issues.

Water budget for the U.S.• ~15.9 trillion liters/day

fall on the U.S. • 66% returned to

atmosphere by evaporation and transpiration

• 3% seeps into groundwater

• 31% as runoff to rivers and lakes

Water Reservoirs

• Rivers

• Lakes

• Wetlands

• Groundwater

• Oceans

• “cryosphere” (glaciers)

Rivers: sources of flow

• Rain falling on the surface of the Earth may infiltrate (to groundwater), runoff (to rivers), or evaporate/

transpirate (to atmosphere).

River discharge

• Amazon, South America 212,400 m3/s• La Plata, South America 79,300 m3/s• Congo, Africa 39,600 m3/s• Yangtze, Asia 21,800 m3/s• Brahmapututra, Asia 19,800 m3/s• Ganges, Asia 18,700 m3/s• Mississippi, North America 17,300 m3/s

• Colorado River, North Am. 300 m3/s

Large rivers of the U.S.

Rivers: Human influences

• Commerce

• Transportation

• Irrigation

• Waste disposal

• Dams diversions

Lakes

• Basins that collect water

• Location of basins defined by geologic setting, presence of water based on climate (local or regional)

• Most of the world’s freshwater resides in lakes

Lakes: Human influences

• Pollution

• Water diversion

• Exotic species

Wetlands• Wetlands are usually inundated by water during some

part of the year, are poorly drained, have low relief, and have high soil moisture.

• Wetlands may appear along coasts as swamps or marshes (i.e. salt marshes) or in the continental interior as marshes, wet meadows, or prairie potholes, or peat moss bogs

http://www.epa.gov/owow/wetlands/

http://www.epa.gov/owow/wetlands/

Natural wetlands have distinct ecosystem functions to which society can assign a “value.”

• nutrient storageremoval of fertilizing nutrients helping farmers to attain compliance with water quality targets

• accumulation of organic material for fuel or agriculturestorage of carbon, source of peat

• filtering of solids from waterswastewater and sewage treatment, trapping sediment

Natural wetlands have distinct ecosystem functions to which society can assign a “value.”

• animal habitatsfishing, wildfowl hunting and fish and shrimp hatcheries. In addition, Wetlands are a home to a third of the nation’s threatened and endangered species.

• plant habitatsforestry, agriculture• regulating water outflowflood and erosion

protection• all functionsrecreation, research, and education

Wetland losses in the U.S.In the 1660’s, 220 million acres of wetlands were thought to exist in the U.S. By 1980, only 103 million acres remained.• Drainage• Dredging• Stream

channelization• Diking, damming• Tilling• Logging• Levees,• Mining nutrient levels• Pollution• Nonnative species

http://www.epa.gov/owow/wetlands/

Groundwater• Water enters the ground as excess surface water• Water then seeps downward due to gravity and the porous

nature of soil, rock, and sediment• Water ultimately seeks it’s base level (usually sea level)

Groundwater Depletion

• Overdraft

• Subsidence

• Saltwater intrusion

Groundwater Pollution• Contaminant transport

Environmental problems related to water usually involve problems with water quantity or water quality.