hydrospheres

The hydrosphere encompasses all water found on Earth, in any form and at any location. It includes oceans, seas, rivers, lakes, groundwater, snow and ice on land, glaciers, the atmosphere's water vapor and clouds, and liquid water within soils and rocks. The hydrosphere interacts continuously with the atmosphere, lithosphere, and biosphere, forming a core component of the global Earth system.

Distribution: About 97.5 percent of Earth's water resides in the oceans as saline water. Freshwater accounts for about 2.5 percent of total water, but most of this is not readily accessible: roughly two-thirds are in glaciers and ice caps, about one-third in groundwater, and a small fraction in surface water such as lakes, rivers, and wetlands. The atmosphere contains a very small, highly variable portion as water vapor and clouds.

Hydrological cycle: The hydrosphere is constantly moved by processes such as evaporation, transpiration, condensation, precipitation, infiltration, runoff, and sublimation. Energy exchanges with the atmosphere drive climate patterns and weather. The cycle transports and stores heat, minerals, and nutrients, shapes landforms, and sustains ecosystems. Ocean salinity gradients, weathering, and groundwater flow link the hydrosphere to other reservoirs.

Human impacts and importance: Human activities influence the hydrosphere through water use, pollution, dam construction, and climate change. Groundwater depletion, river and lake contamination, and changes in precipitation patterns affect water security and ecosystem health. Ongoing monitoring of the hydrosphere informs weather forecasts, climate models, and resource management.