Unit 7
Runoff- water that flows downslope on Earth’s surface and may enter a stream, river, or lake; its rate is influenced by the angle of the slope, vegetation, rate of precipitation, and soil composition.
Watershed- land area drained by a stream system.
Divide- elevated land that divides one watershed from another.
Suspension- the method of transport for all particles small enough to be held up by the turbulence of a stream’s moving water.
Bed load- describes sediments that are too heavy or large to be kept in suspension or solution and are pushed or rolled along the bottom of a streambed.
Discharge- measure of a volume of stream water that flows over a specific location in a particular amount of time.
Flood- potentially devastating natural occurrence in which water spills over the sides of a stream’s banks onto adjacent land areas.
Floodplain- broad, flat, fertile area extending out from a stream’s bank that is covered with water during floods.
Stream channel- narrow pathway carved into sediment or rock by the movement of surface water.
Stream bank- ground bordering each side of a stream that keeps the moving water confined.
Base level- the elevation at which a stream enters another stream or body of water.
Meander- curve or bend in a stream formed when a stream’s slope decreases, water builds up in the stream channel, and moves water erodes away the sides of the streambed.
Delta- triangular deposit, usually made up of silt and clay particles, that forms where a stream enters a large body of water.
Rejuvenation- process during which a stream resumes downcutting toward its base level, increasing its rate of flow.
Lake- natural or human-made body of water that can form when a depression on land fills with water.
Eutrophication- process by which lakes become rich in nutrients from the surrounding watershed, resulting in a change in the kinds of organisms in the lake.
Wetland- any land area, such as a bog or marsh, that is covered in water a large part of the year and supports specific plant species.
Infiltration- process by which precipitation that has fallen on land surfaces enters the ground and becomes groundwater.
Zone of saturation- Region below Earth’s surface where all the pores of a material are completely filled with groundwater.
Water table- upper boundary of the zone of saturation that riser during wet seasons and drops during dry periods.
Zone of aeration- region above the water table where materials are moist, but pores contain mostly air.
Permeability- ability of a material to let water pass through; is high in material with large, well-connected pores and low in material with few pores or small pores.
Aquifers- permeable underground layer through which ground water flows relatively easily.
Aquicludes- layer of impermeable material, such as silt, clay, or shale, that is a barrier to groundwater.
Springs- natural discharge of groundwater at Earth’s surface where an aquifer and an aquiclude come in contact.
Hot springs- thermal spring with temperatures higher than that of the human body.
Geysers- explosive hot spring that erupts regularly.
Wells- deep hole drilled or dug into the ground to reach a reservoir of groundwater.
Drawdown- difference between the water level in a pumped well and the original water-table level.
Recharge- process in which water from a precipitation and runoff is added to the zone of saturation.
Artisan well- fountain of water that spurts above the land surface when a well taps a confined aquifer containing water under pressure.
Cave- a natural underground opening connected to earth’s surface, usually formed when groundwater dissolves limestone.
Sinkhole- depression in Earth’s surface formed when a cave collapses or bedrock is dissolved by acidic rain or moist soil.
Karst topography- irregular topography with sinkholes, sinks, and sinking streams caused by groundwater dissolution of limestone.
Stalactite- cone-shaped or cylindrical dripstone deposit of calcium carbonate that hangs like an icicle from a cave’s ceiling.
Stalagmite- mound-shaped dripstone deposit of calcium carbonate that forms on a cave’s floor beneath a stalactite.