ABSTRACT
Approximately 71% of the earth’s surface is hydrosphere, i.e., covered with water. More than 97% of the earth’s water resides in oceans and saltwater seas. Of the remaining 3%, 2% is distributed in snow and ice, and 1% is distributed in rivers, freshwater lakes and seas, groundwater, and water vapor (Table 10.1). The nature of these water accumulations varies tremendously in physical and chemical characteristics and biology. Variation between and within hydrospheric units depends on climate, depth and topography, underlying geochemistry, access to other bodies of water, and ecological relationship to the adjacent landforms. From a geological point of view, bodies of water and landforms are dynamic and interactive. Snow, ice, and water are part of a vast array of exogenous agents and processes constantly changing the earth’s surface, and being changed by it. Global Water Inventory
Reservoir
Volume (thousand km)
Volume (%)
Rivers
1
0.0001
Atmosphere
13
0.0010
Soil moisture
67
0.0049
Freshwater lakes
125
0.0092
Saline lakes and inland seas
104
0.0076
Groundwater (to 4-km depth)
8350
0.6149
Glacial ice
29,200
2.1504
Oceans
1,320,000
97.2118
Total
1,357,860
100.0001
Source: Adapted from Skinner and Porter (1987).