water cycle
the continual movement of water among Earth's atmosphere, oceans, and land surface through evaporation, condensation, and precipitation
precipitation
any form of water that falls from clouds and reaches Earth's surface
ground water
water that fills the cracks and spaces in underground soil and rock layers
tributary
a stream or smaller river that feeds into a main river
watershed
the land area that supplies water to a river system
divide
a ridge of land that separates one watershed from another
habitat
the place where an organism lives and where it obtains all the things it needs to survive
reservoir
a lake that stores water for human use
wetland
a land area that is covered with a shallow layer of water during some of all the year
permeable
characteristic of a material that is full of tiny, connected air spaces that water can seep through
impermeable
a characteristic of materials, such as clay and granite, through which water does not easily pass
saturated zone
a layer of permeable rock or soil in which the cracks and pores are totally filled with water
water table
the top of the saturated zone, or depth to the groundwater under Earth's surface
unsaturated zone
a layer of rocks and soil above the water table in which the pores contain air as well as water
spring
a place where groundwater flows to the surface
aquifer
an underground layer of rock or sediment that holds water
artesian well
a well in which water rises because of pressure within the aquifer
geyser
a fountain of water and steam that builds up pressure underground and erupts at regular intervals
irrigation
the process of supplying water to areas of land to make them suitable for growing crops
conservation
the practice of using less of a resource so that it will not be used up
water pollution
the addition of any substance that has a negative effect on water or the living things that depend on the water
pollutant
a harmful substance in the air, water, or soil
point source
a specific source of pollution that can be identified
nonpoint source
a widely spread of pollution that is difficult to link to a specific point of origin
water quality
the degree of purity of water, determined by measuring the substances in water besides water molecules
concentration
the amount of one substance in a certain volume of another substance
pH
the measurement of how acidic or basic a substance is on a scale of 0 (very acidic) to 14 (very basic)
hardness
the level of the minerals calcium and magnesium in water
coliform
a type of bacteria found in human and animal wastes
filtration
the process of passing water through a series of screens that allow the water through, but not larger solid particles
coagulation
the process by which particles in a liquid clump together