Sea water contains salts from weathering of minerals from rocks. Sea water is similar in salt concentration as blood. Water with its high heat capacity produces a stable environment. Most fresh water is stored as ice or underground. Surface water seeps downward through soil and porous rock until it reaches impermeable rock or clay.
Unconfined aquifers communicate directly with the surface.
Old river management methods build high levees at the river s edge. They are costly and keep silt in the river channel. New methods build shorter levees away from the river bank creating a flood plain that becomes wetlands and stores water and silt during spring floods. In Ontario, Canada, urbanization changed water runoff patterns. Aquifer depletion in coastal regions causes saltwater intrusion into fresh water well fields.