Hydrology: Science dealing with the properties, distribution, and circulation of water on and below the earth's surface, and atmosphere.Water Cycle: Circulation of water among various ecological systems, in various states, on, above, and below the surface of the earth.Water Movements: The flow of water in enviromental bodies of water such as rivers, oceans, water supplies, aquariums, etc. It includes currents, tides, and waves.Rivers: Large natural streams of FRESH WATER formed by converging tributaries and which empty into a body of water (lake or ocean).SvalbardWetlands: Environments or habitats at the interface between truly terrestrial ecosystems and truly aquatic systems making them different from each yet highly dependent on both. Adaptations to low soil oxygen characterize many wetland species.Ice Cover: A thick mass of ICE formed over large regions of land; RIVERS; LAKES; ponds; or SEAWATER.Soil: The unconsolidated mineral or organic matter on the surface of the earth that serves as a natural medium for the growth of land plants.Climate Change: Any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer). It may result from natural factors such as changes in the sun's intensity, natural processes within the climate system such as changes in ocean circulation, or human activities.Rain: Water particles that fall from the ATMOSPHERE.Ecosystem: A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)Climate: The longterm manifestations of WEATHER. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Biodiversity: The variety of all native living organisms and their various forms and interrelationships.Fresh Water: Water containing no significant amounts of salts, such as water from RIVERS and LAKES.Conservation of Natural Resources: The protection, preservation, restoration, and rational use of all resources in the total environment.Environmental Monitoring: The monitoring of the level of toxins, chemical pollutants, microbial contaminants, or other harmful substances in the environment (soil, air, and water), workplace, or in the bodies of people and animals present in that environment.Population Dynamics: The pattern of any process, or the interrelationship of phenomena, which affects growth or change within a population.Models, Theoretical: Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.Water: A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)