Unit 7

Runoff

Water that flows downslope on Earth’s surface and may enter a stream, river, or lake.

Watershed

Land area drained by a stream system.

Divide

Elevated land that divides one watershed from another.

Suspension

Method of transport for all particles small enough to be held up by the turbulence of a stream’s moving water.

Bed load

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, and the moving water erodes away the sides of the streambed.

Delta

Triangular deposit, usually made up of silt and clay particles, formed 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.

Wetland

Area covered in water a large part of the year that supports specific plant species.

Infiltration

Process by which precipitation 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 rises 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.

Aquifers

Permeable underground layer through which groundwater flows relatively easily.

Aquicludes

Layer of impermeable material that is a barrier to groundwater.

Springs

Natural discharge of groundwater at Earth’s surface.

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 precipitation and runoff is added to the zone of saturation.

Artisan well

Fountain of water that spurts above the land surface from a confined aquifer.

Cave

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.

Karst topography

Irregular topography with sinkholes, sinks, and sinking streams caused by groundwater dissolution.

Stalactite

Cone-shaped or cylindrical deposit of calcium carbonate hanging from a cave’s ceiling.

Stalagmite

Mound-shaped deposit of calcium carbonate forming on a cave’s floor beneath a stalactite.